PL_WI99

Document Sample
PL_WI99 Powered By Docstoc
					                                                SPRAY & DRIP IRRIGATION                                                  Winter 1999




Pipeline
                                                                                                                         Vol. 10, No. 1
                                                                                                                                         SMALL
                                                                                                                                    AL
                                                                                                                                N




                                                                                                                                                 FL
                                                                                                                         O
                                                                                                                       N AT I




                                                                                                                                                     OWS
                                                                                                                       CL




                                                                                                                                                 E
                                                                                                                            E




                                                                                                                                                 S
                                                                                                                                AR               U
                                                                                                                                     INGHO


                                      Small Community Wastewater Issues Explained to the Public

  SPRAY AND DRIP IRRIGATION FOR WASTEWATER REUSE, DISPOSAL
               id you ever wonder how golf         Another benefit of applying wastewater


 D             courses keep their large fair-
               ways looking so lush, healthy,
               and green all season long?
The answer may surprise you.
                                                to land is that the soil provides additional
                                                treatment through naturally occuring
                                                physical, biological, and chemical pro-
                                                cesses. Irrigating with wastewater also
                                                                                                  Treated wastewater can
                                                                                                  be reused to irrigate . . .

  In many communities in the U.S. and           adds nutrients and minerals to soil that are      • lawns;
around the world, treated wastewater is         good for plants, and it helps to recharge         • parks;
reused to irrigate golf courses, lawns,         valuable groundwater resources.
                                                                                                  • landscaped areas around offices
landscaping, forests, and even crops.
Because water is such a precious com-           A Solution for “Problem” Sites                      and industrial developments;

modity, recycling wastewater can have             Irrigation systems often can be used in         • landscaped areas around
both economic and environmental benefits        place of soil absorption fields (drainfields)       residences;
for communities. Irrigation also can be         to provide final treatment and disposal of        • pasture grass;
the most practical and environmentally-         wastewater from individual onsite sys-            • highway medians;
friendly way communities can dispose of         tems, such as septic systems and home
                                                                                                  • golf courses;
treated effluent from wastewater treatment      aerobic treatment units. As the demand
plants and individual home systems.             for land in rural areas is increasing, more       • cemeteries;
                                                sites are being developed in places previ-        • forests;
Better for the Environment                      ously considered unsuitable for onsite
                                                                                                  • trees, corn, alfalfa, and other
  Currently, the most common way com-           systems. Irrigation sometimes is permitted
                                                                                                    feed, fodder, and fiber crops; and
munity treatment plants dispose of waste-       as an alternative wastewater disposal
water after treatment is to discharge it to     method for difficult sites, such as areas         • food crops.
surface waters. However, as populations         with slowly permeable soils, shallow
grow, the burden to local streams and           soils, or complex topographies.
rivers is increasing. Reusing wastewater          This Pipeline issue provides a brief
to irrigate land can help protect precious      overview of two types of wastewater irri-
                                                                                                when they may be a good option for
surface water resources by preventing pol-      gation systems—spray systems and sub-
                                                                                                homes, businesses, and communities.
lution and by conserving potable water for      surface drip systems—how they work,
                                                                                                Operation and maintenance issues also
other uses.                                     their advantages and disadvantages, and
                                                                                                are discussed.
                                                                                                  Readers are encouraged to reprint
                                                                                                Pipeline articles in local newspapers or
                                                                                                include them in flyers, newsletters, or
                                                                                                educational presentations. Please include
                                                                                                the name and phone number of the
                                                                                                National Small Flows Clearinghouse
                                                                                                (NSFC) on the reprinted information and
                                                                                                send us a copy for our files.
                                                                                                  If you have any questions about reprint-
                                                                                                ing articles or about any of the topics dis-
                                                                                                cussed in this newsletter, please contact
                                                                                                the NSFC at (800) 624-8301 or (304)
                                                                                                293-4191.
                                                   SPRAY & DRIP IRRIGATION

         Is irrigating with wastewater a good option
                 for your home or community?
     If you live in an area where water must       is higher quality than the wastewater            system clogging. Additional treatment
  be conserved or is expensive, or where           discharged from treatment plants due to          may be necessary to protect the receiving
  other options for disposing of wastewater        the additional treatment provided in the soil.   environment and may include secondary
  are restricted, then reusing wastewater for         Regulations protect public health and         treatment plus disinfection. This adds to
  irrigation may be a good option for your         the environment by requiring that waste-         the cost of building, operating, and main-
  home, farm, business, or community. It also      water always be pretreated prior to irrigation   taining systems, which should be consid-
  can be a good choice simply because it is        and by restricting its quality, use, and the     ered when determining whether irrigation
  an efficient use of local resources.             manner and location of its application.          is a practical wastewater disposal option.
     In arid climates, such as in Arizona, New     Cumulative levels of nutrients, salts, heavy
  Mexico, and parts of California, for exam-       metals, and disease-causing organisms also       Site Conditions Are Important
  ple, or where the demand for water threat-       must be monitored in the soil at some sites.       Not all sites are appropriate for waste-
  ens to exceed the supply, as it does in parts                                                     water application. Communities wishing
  of Florida, many homes and businesses            Regulations Vary                                 to dispose of wastewater from treatment
  could not afford to maintain grass lawns           Wastewater reuse is not permitted every-       plants through irrigation sometimes must
  or landscaped areas without reusing waste-       where. Regulations vary from state to state      purchase or lease suitable land for dispos-
  water. In Hawaii, treated wastewater is used     and sometimes from community to commu-           al or enter into cooperative arrangements
  to irrigate pineapples and sugar cane to         nity. State and local governments may have       with local farmers or landowners. Sites
  save money and conserve fresh water for          additional or more stringent requirements        near surface water or high groundwater
  other uses.                                      than the federal regulations.                    often are restricted, especially when
     Irrigation also can serve as an alternative     Community residents can contact local          these are used as drinking water sources.
  onsite disposal method for lots deemed           health agency officials to find out about        Regulations typically require minimum
  unsuitable for conventional septic tank/soil     regulations in their area. The National Small    separation distances or buffer zones from
  absorption systems. Because irrigation sys-      Flows Clearinghouse (NSFC) also offers           ground and surface water resources and
  tems are designed to deliver wastewater          information about federal and state regu-        public areas to minimize contact with
  slowly at rates beneficial to vegetation, and    lations. (Refer to the contacts list on page 7   wastewater.
  because the wastewater is applied either to      and the products information on page 8.)           Other important site selection criteria
  the ground surface or at shallow depths,                                                          include the type of soil, soil wetness,
  irrigation may be permitted on certain sites     Pretreatment Is Required                         slope, drainage patterns, and local cli-
  with high bedrock, high groundwater, or             After wastewater receives primary and         mate, including rainfall amounts and
  slowly permeable soils. Irrigation systems       sometimes secondary treatment in a com-          evaporation rates. In areas that have cold
  also can be designed to accommodate sites        munity treatment plant or individual onsite      or wet weather part of the year, waste-
  with complex terrains.                           treatment system, additional treatment steps     water often must be stored in lagoons or
     Local governments sometimes choose            often are required prior to irrigation to        holding tanks until irrigation is needed.
  to reuse wastewater from community               reduce the amount of suspended solids and        Some irrigation equipment also can freeze
  treatment plants for irrigation, rather than     organisms in the wastewater. Both can pose       in very cold weather.
  discharging all of it to local surface waters.   a threat to public health and clog systems.
  Irrigation can help communities to save          Microorganisms, such as bacteria, can col-       Maintenance Is Necessary
  money or avoid exceeding surface dis-            lect or multiply and create slime that clogs        All systems, including irrigation sys-
  charge permit limits, while preserving           systems. Pretreatment also minimizes odors       tems, have operation and maintenance
  the quality of local water resources for         in wastewater, so there is less potential for    requirements. These include periodic
  drinking water, aquatic life, and recreation.    creating a public nuisance and attracting        checking and cleaning of filters, checking
  Some communities even have two sep-              animals that can spread diseases.                valves, pumps, and timers, and, in some
  arate distribution systems—one for                 Different degrees of pretreatment are          cases, monitoring wastewater quality and
  potable water and another for reclaimed          required for the wastewater depending on         its impact on soils. Large systems serving
  water for watering lawns and other               how it will be used and the intended method      farms, businesses, or communities often
  irrigation needs.                                of irrigation. For example, standards are        have operators, but most systems are at
                                                   more rigorous for surface irrigation methods,    least partially automated.
  Is it safe?                                      such as spray irrigation, and when irrigating       Although spray and subsurface drip
    Irrigating with wastewater is safe when        food or feed crops or land intended for pub-     irrigation systems serving individual
  all federal, state, and local regulations        lic use. Biological pretreatment to remove       homes may only need maintenance about
  regarding its treatment and use are strictly     organic matter from the wastewater is fol-       once or twice per year, homeowners
  followed. When regulatory requirements           lowed by filtration, to remove small parti-      should consider that these systems will
  are met, the wastewater returned to the          cles from the wastewater, and disinfection.      require more attention than conventional
         environment after irrigation usually        Subsurface drip irrigation systems also        onsite systems.
  2                                                employ filters mainly to protect against
PIPELINE - Winter 1999; Vol.10, No. 1                                                                 National Small Flows Clearinghouse 1-800-624-8301
                                                  SPRAY & DRIP IRRIGATION

                    Spray Systems Irrigate Lawns, Parks, Crops
                                        1   House Sewer        3       Septic Tank       5   Sand Filter          7   Pump Chamber

         Example                        2   Septic Tank        4       Dosing Tank       6   Cl2 Disinfection     8   Spray System


         residential
         spray system
                                                    1
         schematic                                                                                                                   8

                                                                   2         3

                                                                                     4         5           6           7




     Spray irrigation is an efficient way to          Chlorination is the most common disin-                 Another design used to irrigate row
  nourish plants and apply reclaimed waste-         fection method used with spray irrigation.             crops, called a portable irrigation reel, is
  water to land. Some spray systems are             One common chlorinator design accepts                  a little less high-tech. It consists of a hard
  very similar to potable-water sprinkler           chlorine tablets or powder; another doses              plastic hose wound to a drum reel. One
  systems used to irrigate lawns. Others            liquid chlorine into the wastewater. With              end of the hose is attached to a portable
  are specifically designed for agricultural        chlorination, adequate contact time is                 sprinkler cart, which is pulled away from
  applications.                                     necessary to allow the chlorine time to                the reel during setup, and the other end of
    While there are many possible spray sys-        kill harmful bacteria and other pathogens.             the hose is attached to a hydrant. A motor
  tem designs, they all work by distributing          A holding tank or lagoon is another nec-             or turbine rewinds the reel and crops are
  treated wastewater across the soil surface.       essary component in most spray systems,                irrigated as the sprinkler cart moves along
  Systems should be designed by qualified           because storage space allows operators to              the uncultivated irrigation paths, which
  professionals who have specific experience        adjust application rates, if needed. In                must be kept clear for this purpose.
  working with irrigation systems.                  some onsite systems that employ a recir-                 There also is a variety of sprinkler
                                                    culating sand filter, the recirculation tank           designs for irrigating smaller field crops,
  System Design                                     serves as the storage tank. However, spray             lawns, and landscaping, which are similar
    Because spray systems apply effluent            systems in cold or wet climates may need               to potable-water lawn sprinkler systems.
  above-ground, the wastewater must be              to store 130 days of design flow or more.              The sprinklers can be fixed (called solid-
  treated to a high enough level to protect         Systems may be permitted to apply waste-               set) or moveable, buried or above-ground,
  public health and reduce odors. In general,       water only certain months of the year, or              and some designs are telescoping to adjust
  regulations require that effluent used for        they may be required to include subsur-                the height of application to fit the height
  surface irrigation at least meet secondary        face drainage to help prevent runoff and               of the plants. Other variations exist in
  treatment standards plus disinfection.            erosion during wet weather.                            the amount of pressure and manner in
    With spray systems, therefore, after              Large community systems sometimes                    which the wastewater is released from the
  primary treatment in a septic tank or com-        reduce the amount of storage area they                 sprinklers—examples include full circle,
  munity treatment plant, the wastewater            need by obtaining controlled discharge                 partial circle, gun, and microspray. Dif-
  usually goes to a home aerobic treatment          permits, which allow them to release                   ferent pressure amounts are appropriate
  unit, sand filter, recirculating sand filter,     wastewater to surface water in winter or               for irrigating different plant types. Indi-
  or other filter, and then to a dosing tank        during times of high stream flows.                     vidual home systems use low trajectory
  or pump chamber. The wastewater is then                                                                  sprinklers to minimize aerosol production.
  disinfected with chlorine, ozone, or ultra-       Spray Equipment                                          Fixed, buried sprinkler systems usually
  violet light before it is stored in a lagoon        There is an impressive array of high-tech            are among the most expensive designs to
  or holding tank for later use or just prior       spray equipment available for irrigating               purchase and install, but they have certain
  to its application to land. In some com-          crops. Some consist of series of sprinkler             advantages. They are less likely to be van-
  munity systems, aerated or facultative            heads mounted to elevated distribution                 dalized or accidently damaged and they
  lagoons provide treatment as well as              pipes, which move across fields either                 make maneuvering farm equipment and
  additional storage area for the wastewater.       laterally, by means of drive units at both             lawn mowers easier. However, some
    After treatment, filtration, and disinfec-      ends of the pipe (called linear move), or              moveable system components can be
  tion, a pump equipped with timers sends           in a circular motion from one fixed end                stored indoors in the winter. Most spray
  the wastewater under pressure through the         (called pivot move). The height and                    system designs include valves and con-
  mains and lines of the spray distribution         amount of pressure with which the spray                trols that allow operators or homeowners
  system at preset times and rates as needed        nozzles emit wastewater can be adjusted.               to adjust the flow to certain areas of the
  for irrigation. The area to be irrigated          Systems even can be programmed to                      spray field. Some larger systems have
  (the spray field) can be sloped up to 30          adjust application rates for different parts           both automated and manual controls.
  percent, depending on local regulatory            of the field and to shut off automatically             continued on page 4
  requirements, but must be vegetated and           during rain or high winds. And some can
  landscaped to minimize runoff and erosion.        be operated remotely.
                                                                                                                                                      3
PIPELINE - Winter 1999; Vol.10, No. 1                                                                       National Small Flows Clearinghouse 1-800-624-8301
                                        SPRAY & DRIP IRRIGATION

Some Advantages of Spray                Spray Systems Irrigate                                Farmers must schedule irrigation times
                                                                                           and rates carefully, always adjusting for
Systems Include . . .                   Lawns, Parks, Crops                                different rainfall and evaporation amounts.
                                                                                           Some use devices, such as tensiometers,
                                        continued from page 3
• When properly designed,                                                                  to measure soil wetness, and rain gauges
  installed, and operated, most
  spray systems provide uniform
                                        Setbacks and Buffer Zones                          and pan evaporation tests to keep track of
                                          To guard against the possibility that            irrigation needs. Spray irrigation of crops
  distribution of wastewater to                                                            also needs to be scheduled around applica-
  plants and eliminate discharge        drifting aerosols and runoff created by
                                        spray irrigation systems will reach and            tions of pesticides and fungicides to plants.
  to streams.                                                                                 Scheduling the irrigation of other types
• Above-ground irrigation is need-      contaminate nearby public areas and
                                        water resources, regulations typically             of spray fields is usually less complicated.
  ed for some germinating plants.
                                        require considerable minimum setback               Unrestricted public access sites, such as
• Spray irrigation increases levels
                                        distances or buffer zones to nearby resi-          the lawns of homes or businesses, land-
  of nitrogen, phosphorus, and
                                                                                           scaping, parks, highway medians, and golf
  minerals in the soil.                 dences, property lines, public areas, wells,
• Above-ground spray system             streams, rivers, lakes, and wetlands.              courses, often are irrigated only at night or
  components are easier to              Minimum setbacks of as much as 150 to              during off-hours to minimize the potential
  inspect, control, and service         500 feet from neighboring residences and           for public contact with the wastewater.
  than subsurface drip irrigation       water sources are not unusual, depending           Small systems and systems serving indi-
  components.                           on local regulations. Buffers also may be          vidual homes often are designed to apply a
• When performed during the             required from water lines, embankments,            set amount of wastewater twice a week or
  heat of the day it has a cooling      drains, drainage ditches, and public rights        so at predetermined rates and times. The
  effect on some crops and deco-                                                           system designer estimates the amount
                                        of way. A minimum vertical separation
  rative landscape plants.                                                                 needed based on records showing average
                                        distance to the water table also applies.
• Evaporation contributes to the                                                           precipitation and evaporation rates in the
                                          Because of these setback requirements,
  rate of wastewater disposal.                                                             area. Homeowners usually can adjust or
                                        spray systems tend to be mainly practical
                                        for irrigating crops, fields, and larger land      override the pump settings if needed.
Some Disadvantages of                   areas or home lots.                                   If a system is designed and sized primarily
Spray Systems Include . . .                                                                for wastewater disposal, the loading rates
                                        Operation and Scheduling                           permitted for the wastewater may be below
• Spray systems generate                   Unlike traditional irrigation systems           the irrigation needs of the plants. Therefore,
  aerosols, which can pose a            whose sole purpose is to deliver water to          additional water may be required for irriga-
  threat to public health. Therefore,   plants, several additional factors must be         tion with some systems.
  regulations typically require large
                                                                                           Monitoring and Maintenance
                                        considered when managing wastewater
  minimum setback distances,
                                        irrigation systems. The timing and rate of
  buffers, and other restrictions                                                             The pump, disinfection system, and
                                        wastewater application must be designed so
  that make spray systems                                                                  spray heads in spray irrigation systems
  inappropriate for small lots.         that plants benefit as much as possible from
                                        the nutrients and other constituents in the        require regular maintenance. For example,
• Wet soil surface promotes weed                                                           the chlorine tablets in chlorinators need to
  growth, making some crops and         wastewater without being overwhelmed by
                                        them. In addition, there is the potential that     be replenished regularly—approximately
  landscaping difficult to maintain.
                                        certain wastewater constituents may accu-          once per month for home systems. Open
• Wet soil surface makes weeding,
                                        mulate in the soil and plants over time and        pipes and spray heads can become dam-
  harvesting, and operating lawn
                                                                                           aged, plugged, or frozen. Any changes in
  mowers and farm equipment             become toxic to the plants, clog the soil, or
  more difficult.                       alter the soil structure.                          pressure in the system can alter the spray
• Applications of insecticides and         For example, too much nitrogen can result       patterns in the field, so spray patterns
  fungicides to crops must be           in nitrate accumulation in crops, but too little   should be tested to ensure that the system
  scheduled carefully between           can result in reduced yields. If evaporation       still complies with all setback requirements.
  spray irrigation applications to      regularly exceeds precipitation, too much             Other monitoring requirements vary
  allow maximum contact/                salt may remain in the soil, which can             depending on state and local regulations,
  exposure times.                       damage roots. The particular characteristics       public access to the site, and system size.
• Above-ground spray equipment                                                             In some systems, regular daily or weekly
                                        of the wastewater must be considered in
  is exposed to the elements and                                                           monitoring is needed to check influent
                                        relation to such factors as climate and the
  can be accidentally damaged or                                                           and effluent quality, system storage capac-
                                        individual nutrient requirements of the
  vandalized.                                                                              ity, wind speed and direction, signs of
• Bacteria tends to survive better      crops, grass, or landscape plants selected.
                                           In addition, the need to dispose of the         ponding or runoff in the spray field, and
  in wet, cool soil conditions.                                                            depth to water table. Cumulative levels of
                                        wastewater has to be balanced with the
                                        needs of the plants during various stages          nutrients, heavy metals, fecal coliforms,
                                        of growth and the hydraulic capacity of the        and other wastewater constituents must be
                                        soil and its ability to effectively provide        monitored in the soils (and groundwater)
  4                                     treatment.                                         at some sites once or twice per year.

PIPELINE - Winter 1999; Vol.10, No. 1                                                        National Small Flows Clearinghouse 1-800-624-8301
                                                 SPRAY & DRIP IRRIGATION

       Subsurface Drip Irrigation Systems Have Many Advantages

     Drip irrigation systems (also known as        Drip system emitters are designed to          to groundwater. (Refer to page 6 for a list
  “trickle” systems) are another efficient       ensure that the wastewater is always            of some advantages and disadvantages of
  and proven technology many small com-          released at the same slow rate at atmos-        subsurface drip systems.)
  munities can chose to recycle and dispose      pheric pressure, even though the water
  of wastewater. Drip irrigation technology      pressure inside the tubes can range from 5      Other System Design Elements
  using treated wastewater is used in Israel     to 70 pounds per square inch (psi) during          As with spray irrigation systems, waste-
  and throughout the world as a way to con-      a dosing cycle. However, most systems           water must be pretreated prior to drip
  serve water resources. These systems           are engineered to maintain relatively con-      irrigation to protect public health and the
  require less water than spray systems to       sistent pressure inside the tubes, usually      environment and to prevent systems from
  irrigate plants, and the technology has been   about 20 psi. The pressure-compensating         clogging. Settleable and floatable solids are
  used for more than 30 years for various        feature of emitters allows drip irrigation      removed by primary treatment, which may
  agricultural and landscape applications.       lines to be installed at different elevations   take place in a community treatment plant
                                                 at a site while maintaining uniform flow.       or lagoon or on individual home lots in a

  Subsurface Drip Systems                          Because subsurface drip systems release
                                                 wastewater below-ground directly to plant
                                                                                                 septic tank or home aerobic treatment unit.
                                                                                                 Primary treatment always is followed by
  Deliver Effluent to Plant Roots                roots, they irrigate more efficiently and       filtration in a particle-size filter to protect
    With drip systems, treated wastewater is     have advantages different from those of         the tubing from clogging.
  applied to soil slowly and uniformly from      surface irrigation systems. For example,           In most systems, effluent flows to a tank
  a network of narrow tubing (0.5- to 0.75-      the soil surface tends to stay dry, which       or pump chamber equipped with controls,
  inch diameter), usually plastic or polyeth-    means there is less water lost to evapora-      where it is stored until a predetermined
  ylene, placed either on the ground surface     tion and there is almost no opportunity for     dosing volume is reached. All drip systems
  or below ground at shallow depths of 6 to      the wastewater to come in contact with          are equipped with a filtration system before
  12 inches in the plant root zone. The          plant foliage, humans, or animals. Also,        the distribution system, such as a series of
  wastewater is pumped through the tubes         percolation losses are reduced because the      disc filters or mesh screen filter membranes,
  under pressure, but drips out slowly from      wastewater is applied to a wide area of         to remove small suspended solid materials
  a series of evenly-spaced openings. The        soil at a slow rate directly to plant roots.    from the wastewater that can clog tubes
  openings may be simple holes or, as is           In addition, in drip systems the waste-       and emitters. Some systems also include
  the case in most subsurface systems, they      water is delivered to the most biologically     a disinfection step to protect public health.
  may be fitted with turbulent flow or pres-     active part of the soil, which enhances            The U.S. Environmental Protection
  sure-compensating emitter devices. These       treatment and minimizes the possibility of      Agency approves the use of the chemical
  emitter designs are proprietary and vary       groundwater contamination. The constant         trifluralin to prevent root intrusion into
  depending on the manufacturer of the           moisture in the root zone also may              emitters, although some states may not
  system. (The graphic below is meant            increase the availability of nutrients to       permit it. One manufacturer of drip system
  to illustrate a generic subsurface drip        plants, reducing the delivery of nitrogen       tubing incorporates a chemical barrier to
  tube design.)                                                                                  root intrusion directly into the tubing mate-
                                                                                                 rial itself. However, the consistently wet
                                                                                                 conditions in the soil and the pressure
   Example drip tubing                                                                           compensating emitter design discourages
                                                                                                 root growth into the distribution lines.
                                                                                                    The distribution system in subsurface
                                                                                                 drip systems usually includes a mainline,
                                                                                                 submain, and narrow drip laterals with
                                                                                                 emitters. The total length of drip tubing
                                                                                                 will depend on the restrictiveness of the
                                                                                                 site, the area needing irrigation, and the
                                                                                                 amount of storage space available. The
                                                                                                 laterals normally are installed in narrow
                                                                                                 trenches (approximately 10 centimeters
                                                                                                 wide) dug with a vibratory plow. Because
                                                                                                 of the flexibility of the laterals and their
                                                                                                 shallow placement, drip lines can be laid
                                                                                                 around trees and other topographic features
                                                                                                 with little disturbance to the site.
                                                                                                 continued on page 6
                                                                                                                                            5
PIPELINE - Winter 1999; Vol.10, No. 1                                                             National Small Flows Clearinghouse 1-800-624-8301
                                             SPRAY & DRIP IRRIGATION

Advantages of Subsurface
                                                                                               scale buildup develops on emitters, an
Drip Systems Include . . .                   Subsurface Drip                                   acid treatment may be necessary.
• Water and nutrients are delivered
                                             Systems Have Many
                                                                                               Setbacks and Buffer Zones
  directly to plant roots.
• Less water is required when irri-
  gating with drip systems than with
                                             Advantages                                          As with spray irrigation systems, regu-
  spray systems and other suface             continued from page 5                             lations typically require that drip systems
  irrigation methods.                                                                          be installed at minimum distances from
                                               The submains supply the amount of
• Wastewater is distributed more                                                               nearby residences, property lines, public
  evenly with drip systems than              water required by the individual laterals it
                                             feeds, and valves are located between the         areas, wells, surface water resources, and
  spray systems and open irrigation
  trenches.                                  main and the submains to control the flow         groundwater. However, because drip sys-
• Evaporation losses and weed                of water to different parts of the system.        tems deliver wastewater below ground
  growth are reduced because the                                                               and do not produce aerosols, buffer zones
  soil surface remains dry.
• Operating lawnmowers and farm
                                             Clogging                                          of 25 to 50 feet are generally required to
                                               Drip system emitter clogging was more           neighboring residences—considerably
  equipment is easier because system
                                             of a problem in the past than it is today.        less than is required for spray systems,
  components are buried and the soil
  surface stays dry.                         Root intrusion into the drip tubing and           making drip disposal more practical for
• There is no aerosol generation and no      internal clogging from the buildup of sed-        smaller home lots.
  wastewater contact with plant foliage.     iment, suspended solids, algae, and bacte-
• Crops irrigated with drip systems          rial slime have been diminished greatly by        Operation, Maintenance, and
  can be harvested sooner than when
                                             better pretreatment, filtration, disinfection,    Scheduling
  irrigated with spray systems.                                                                  As with spray systems, drip irrigation
• Fewer problems exist with odors,           and new tubing and emitter designs. Most
                                             systems allow weekly or biweekly forward          must be scheduled so that plants benefit
  ponding, and runoff.
• There is less chance of wastewater         flushing of the tubes to scouring velocity to     from the nutrients and other constituents
  carrying additional chemicals, such as     remove slime and sediment buildup.                in the wastewater without being over-
  pesticides and fungicides, from the          The size of the emitter orifices also is        whelmed by them, and the needs of the
  ground surface to groundwater.                                                               plants must be balanced with the capacity
                                             important to prevent clogging and should
• Studies suggest nitrogen in wastewater                                                       of the soil to treat the most restrictive
  may be better absorbed by plants and       range from four to six times the maximum
                                             size of the particles that can pass through       components in the wastewater. These
  less likely to pollute groundwater when
  applied directly to plant roots.           the mesh of the filter screen preceding the       concerns must be balanced in turn with
• In some cases, fewer pretreatment          distribution system. For example, a system        climate and other site factors.
  steps are required for wastewater with     using a filter screen size of 115 microns           Less labor usually is required for oper-
  drip systems.                                                                                ating and maintaining fixed subsurface
                                             (140 mesh) should have emitters approxi-
• It is less likely that subsurface drip                                                       drip system components as compared to
  components can be accidently or            mately 800 microns in diameter to achieve
                                             about a six-to-one ratio.                         spray systems and surface drip systems
  intentionally damaged.
• Flexible tubing can accommodate sites        When even a few emitters do clog, it can        with moveable components. For small
  with complex topographies.                 affect the pressure inside the tubes and the      and individual home systems, the pattern
• There are generally fewer operation        uniformity of wastewater distribution in          of flow may be fixed or adjusted manual-
  and maintenance requirements than          the field. It also may be difficult to identify   ly or automatically by the homeowner
  with spray systems.                                                                          or operator, depending on the system
                                             and service buried emitters that clog. And
                                             like traditional soil absorption systems          design and sophistication. In general, the
Disadvantages of Subsurface                  used with septic systems, saturation of the       best care for subsurface drip systems is
Drip Systems Include . . .                   soil around the emitters of a drip system         provided by following the individual
• Emitters can potentially clog, affecting   can eventually lead to the formation of a         manufacturer recommendations.
  the uniformity of application.             biological clogging mat, which can cause            Some communities may require home-
• Temporary use of sprinklers or other       system failure. However, in general, sub-         owners and small system owners to main-
  surface irrigation may be necessary                                                          tain a service contract with an authorized
  during plant germination period.
                                             surface drip systems are considered to be
                                             a manageable and reliable technology.             manufacturer’s representative to ensure
• It is difficult to monitor and correct
                                               Filters on all drip systems need to be          appropriate monitoring and maintenance.
  potential emitter clogging.
• Effects of freezing temperatures on        checked and periodically backflushed or           Larger systems often have full-time oper-
  drip systems and applying wastewater       cleaned. Backflushing reverses the water          ators to maintain and service systems and
  to frozen ground is still the subject of   flow through the lines and the filters to         to control the pattern of wastewater flow
  study and debate.                                                                            to irrigate different crops or fields. Some
                                             release trapped sediments. Some systems
                                             can be set up to backwash automatically           systems can be operated and monitored
                                             at preset intervals, or operators can do it       remotely through telemetry.
                                             manually as needed. The wastewater flow             Refer to the list of NSFC documents on
                                             needs to checked periodically to deter-           page 8 and the list of contacts on page 7
                                             mine if any emitters are plugging. If a           for more detailed information on subsur-
    6                                                                                          face drip systems.
 PIPELINE - Winter 1999; Vol.10, No. 1                                                           National Small Flows Clearinghouse 1-800-624-8301
                                                 SPRAY & DRIP IRRIGATION



      Wisconsin Drip System Is an “Educational Opportunity”
     If you were to pinpoint the center of          “Because we are working with the uni-
  Wisconsin on a map, you just might find        versity, we were able to get an experimen-
  Nasonville Elementary School. Located          tal permit for a drip system,” Rodenbeck
  in the rural Marshfield School District,       said. “Graduate students from the univer-

                                                                                                   CONTACTS
  in the middle of dairy country, Nasonville     sity regularly monitor the system’s per-
  has plans to consolidate with another local    formance, which is good for us and an
  school adding 67 students to the 95 cur-       educational opportunity for them.”
  rently enrolled. But before health officials
  would approve the additional students, the
                                                    Nasonville’s new system is sized to
                                                 handle 2,500 gallons of wastewater flows
                                                                                                 The National Small Flows
  school needed to upgrade its old waste-        per day, which is enough to accommodate         Clearinghouse (NSFC)
                                                                                                 The NSFC offers technical assistance and
  water system.                                  approximately 350 students. Rodenbeck
                                                                                                 free and low-cost information about onsite
     “In our part of Wood County, we have        estimated the system size needed by             and small community wastewater techno-
  some of the densest clay soils ever seen,”     checking daily water use at other area          logies and issues, including spray and drip
  explained Paul Rodenbeck, the school dis-      schools. The system consists of a 3,000-        irrigation, wastewater reuse, and state and
  trict’s building and grounds director. “For    gallon septic tank equiped with a Zabel™        federal regulations. Only a few of the NSFC’s
  years, the school’s wastewater system          filter at the outlet. From the septic tank      many resources and services are mentioned
                                                                                                 in this issue. Visit the NSFC’s Web site at
  consisted of a septic tank that discharged     the wastewater flows to a recirculation         www.nsfc.wvu.edu, or call (800) 624-8301 or
  across an open field. Because of the diffi-    tank where the wastewater is pumped to a        (304) 293-4191 for assistance or to request a
  cult local site conditions (heavy silt loam    recirculating gravel filter. After treatment    free catalog.
  over massive clays), our options for           in the gravel filter, the wastewater returns
  upgrading were somewhat limited.”              to the recirculation tank and then flows to     Local and State Health Agencies
     Holding tanks are the only new onsite       an intermediate settling tank equipped          For more information about spray and drip
  wastewater systems being permitted in the      with another Zabel™ filter at the outlet.       irrigation, local regulations, or permit require-
  area. But Rodenbeck, a former municipal        Next, the wastewater flows to a dosing          ments, community residents should contact
                                                                                                 their local or county health department
  wastewater treatment plant operator, was       tank where it is sent to the drip distribu-
                                                                                                 officials. Community leaders who wish to
  inspired to research possible onsite waste-    tion system.                                    evaluate irrigation as an alternative to direct
  water treatment alternatives for the school.      “The system is designed to dose over         discharge should contact their state health
     One option that may have been appropri-     a 24-hour period,” explained Rodenbeck.         agency. State and local agencies usually are
  ate for Nasonville was a mound system,         The drip system itself has four zones or        listed in the government section or blue
  but the school was not keen on the way         cells and takes up about one acre of the        pages of local phone directories.
  it might look on the school grounds, the       10-acre school lot.
  earthwork involved, or the prospect of            Rodenbeck said that the system has           Extension Service Offices
                                                                                                 Many universities have U.S. Department
  having to mow it. Repair costs were anoth-     been working well. “Due to mechanical
                                                                                                 of Agriculture Extension Service offices on
  er concern. “Even if only one part of the      problems, the gravel filter was taken out       campus and in other locations, which provide
  system needs to be repaired, the mound         of service during the winter, and we had        a variety of services and assistance to indi-
  has to be dug up,” Rodenbeck said.             to bypass the filter all together,” he said.    viduals and small communities. For the
     Rodenbeck’s inquiries led him to work       “The university requested that we not fix       number of the Extension Service office in
                                                                                                 your area, check the government pages of
  with Duane Grueul of the Wood County           this problem, but, instead, operate the
                                                                                                 your local phone directory, call the NSFC,
  Planning and Zoning Department. Grueul         system with just the septic tank effluent       or call the U.S. Department of Agriculture
  suggested several area design firms that       going through the drip system filters and       directly at (202) 720-3377.
  have experience with onsite systems. He        then to the drip lines. The system has
  also introduced Rodenbeck to Dr. James         been working fine this way. None of the         The Irrigation Association (IA)
  Converse of the University of Wisconsin’s      emitters have plugged and I haven’t even        The IA is the irrigation industry’s trade organi-
  Small Scale Waste Management Project,          had to clean the filters. The gravel filter     zation and has members who can provide
                                                                                                 professional assistance in all aspects of irri-
  one of the first research programs in the      will be modified and be online for the start
                                                                                                 gation. IA members include researchers,
  country to study onsite systems.               of school.”                                     technicians, manufacturers, distributors, deal-
     The firm the school chose for the proj-        The university students continually          ers, system designers, consultants, installers,
  ect, Ayres and Associates of Madison,          monitor the performance of the system           and contractors. Visit its Web site at www.
  worked together with Dr. Converse,             and levels of bacteria in the soil as well as   irrigation.org to conduct a search of IA’s
  Grueul, and Rodenbeck to design a solu-        investigate the effect of temperature on        membership or for consumer information,
                                                                                                 including how to hire an irrigation contractor.
  tion for the site—namely, a subsurface         the levels of bacteria in the soil.
                                                                                                 Or, contact IA headquarters in Fairfax,
  drip system. The system was installed in          To learn more about Nasonville’s system      Virginia, at (703) 573-3551 for assistance.
  August 1998 and is part of the University      and the University of Wisconsin study, con-
  of Wisconsin’s research project.               tact Dr. Converse at (608) 262-1106.
                                                                                                                                               7
PIPELINE - Winter 1999; Vol.10, No. 1                                                             National Small Flows Clearinghouse 1-800-624-8301
    RESOURCES AVAILABLE FROM NSFC
                                                 SPRAY & DRIP IRRIGATION



  To order any of the following products,        Computer Search: Drip Irrigation               Free Brochure: Water Reuse Via Dual
  call the National Small Flows Clearing-        This booklet is a compilation of article       Distribution Systems
  house (NSFC) at (800) 624-8301 or (304)        abstracts on drip irrigation compiled from     This free brochure examines the benefits
  293-4191, fax (304) 293-3161, e-mail           a search of the NSFC’s Bibliographic           of a wastewater reuse system and includes
  nsfc_orders@estd.wvu.edu, or write             Database. Complete copies of the articles      information on system operation, design,
  NSFC, West Virginia University, P.O. Box       can be ordered from the NSFC. The price        cost, and public acceptance issues.
  6064, Morgantown, WV 26506-6064. Be            is $2.75. Request Item #WWBLCM18.              Request Item #WWBRGN15.
  sure to request each item by number and
  title. A shipping and handling charge                                                                                              PIPELINE
  will apply.                                    Computer Search: Spray Systems                                     L   SMALL
                                                                                                                 NA
                                                 Spray systems as an alternative to conven-




                                                                                                                                FL
                                                                                                             O




                                                                                                                                  OW
                                                                                                       NAT I
  Spray and Drip Irrigation Technology




                                                                                                                                    S
                                                 tional methods of wastewater disposal is
                                                                                                                                               an equal opportunity/affirmative action




                                                                                                                                 E
                                                                                                        CL
  Package                                        the topic of this NSFC Bibliographic                        EA




                                                                                                                                S
                                                                                                                   R IN GHOU                                institution
                                                 Database search. Abstracts of spray system      Pipeline is published quarterly by the National Small
  A selection of useful articles about spray                                                       Flows Clearinghouse at West Virginia University,
                                                 articles are included. The price is $6.75.
  and drip irrigation with wastewater is pre-                                                       P.O. Box 6064, Morgantown, WV 26506-6064
                                                 Request Item #WWBLCM19.
  sented in this publication. The articles are
                                                                                                                      Pipeline is sponsored by:
  chosen from the NSFC’s Bibliographic                                                                           U.S. Environmental Protection Agency
  Database. Onsite irrigation systems and        Manufacturers and Consultants Database                                     Washington D.C.
                                                 Customized searches of the NSFC’s                                   Steve Hogye—Project Officer
  the application of wastewater to forest                                                                              Municipal Support Division
  lands and parks are among the topics dis-      Manufacturers and Consultants Database                           Office of Wastewater Management
  cussed. Case studies also are included.        are available upon request. Contact the
                                                                                                             National Small Flows Clearinghouse
  The price is $16.25. Request Item              NSFC and ask to speak with a technical                              West Virginia University
  #WWBKGN53.                                     assistance specialist to request a search of                           Morgantown,WV
                                                 irrigation system manufacturers, dealers,                   Peter Casey—Program Coordinator
                                                                                                           Andrew Lake—Special Technical Advisor
                                                 designers, consultants, and operators in
  Guidelines for Water Reuse                     your area. The price varies. Request Item
                                                                                                               Cathleen Falvey—Writer/Editor
                                                                                                                Jill A. Ross—Associate Editor
  This EPA manual presents federal guide-                                                                      Kairi Frame—Graphic Designer
                                                 #WWPCCM16.
  lines for implementing a water reuse sys-                                                         Permission to quote from or reproduce articles in
  tem and how to evaluate water reclamation                                                     this publication is granted when due acknowledgement
  and reuse opportunities. Chapters are          Guide to State Level Onsite Regulations           is given. Please send a copy of the publication in
                                                 This guide provides information about            which information was used to the Pipeline editor at
  devoted to each of the technical, financial,                                                                      the address above.
  legal, institutional, and public involve-      state regulations regarding onsite waste-                                  ISSN 1060-0043
  ment considerations that a reuse planner       water systems. Contacts, keywords, and             Pipeline is funded by the United States Environmental Protection
                                                                                                  Agency. The contents of this newsletter do not necessarily reflect the
  might examine.The price is $30.00.             definitions are included. The price is           views and policies of the Environmental Protection Agency, nor does

  Request Item #WWBKDM72.                        $12.50. Request Item #WWBKRG01.                     the mention of trade names or commercial products constitute
                                                                                                                 endorsement or recommendation for use.

                                                                                                                                    Printed on recycled paper




           For wastewater information, call the NSFC at (800) 624-8301 or (304) 293-4191




                                                                                           ADDRESS SERVICE REQUESTED
 Morgantown, WV                                                                       Morgantown, WV 26506-6064
  Permit No. 34                                                                       P.O. Box 6064
  8
U.S. Postage Paid
Nonprofit Organization
                                                                                      West Virginia University
                                                                                      National Small Flows Clearinghouse
PIPELINE - Winter 1999; Vol.10, No. 1                                                            National Small Flows Clearinghouse 1-800-624-8301

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:2/6/2012
language:
pages:8