Household Wastewater Treatment S by fjzhangweiqun


									  Household Wastewater Systems
                    Mike Kizer
OSU Extension Biosystems & Agricultural Engineering
       Typical Waste Water System


               Renovated Wastewater
 Wastewater System Regulation
• Regulatory agency in Oklahoma is:
  Department of Environmental Quality (DEQ)
  707 N. Robinson, OKC (Tel: 405-702-6100)
• DEQ field offices in many counties
 Check local listing under: Oklahoma – State of –
• Regulations are outlined in Title 252 of
    Oklahoma Administrative Code, Ch. 641
• DEQ wastewater system website:
    Minimum Lot Size for
  Wastewater Disposal Systems
  Disposal System            Water Supply Source
       Type               Private Well Public Supply
Aerobic w/ sprinklers        ¾ acre        ½ acre
ET/Absorption Trench         1 acre        1 acre
Subsurface (fast perc.)      ¾ acre        ½ acre
Subsurface (slow perc.)      1 acre        1 acre
Lagoon                      2 ½ acres    2 ½ acres
Wastewater System Separation Distances
                                   (distance in feet)

                      Tanks        Perforated   Solid Pipe   Lagoon     Sprinkler   Spray
                  (septic, pump,    Pipe or                              Head       Head
                     aeration)     Chamber

Private Well        50 / 100       50 / 100     50 / 100     50 / 100   50 / 100     15

Public Well           300            300           50          300        300        15

Buildings               5              5           NA          50         NA        NA

Other Structure        NA             10           NA          NA         NA        NA

Water Line              5             15           10          15          15       NA

Property Line           5              5            5          10          5         5

Stream/Lake            15             15           NA          15          15        15

Drains                 15             15           NA          15         NA         15
Wastewater System Components
• Water-tight sewer lines
• Septic tank
• Disposal system
  – Subsurface drain field
       • Absorption trenches
       • Infiltration chambers
  –   ET/Absorption trenches
  –   Aerobic system with sprinkler
  –   Total retention lagoons
  –   Pre-approved alternative disposal systems
                                                  Screen vent pipe opening to prevent
                                                  blockage by birds, squirrels, etc.

Household Plumbing
Sewer and Vent System
•Sewer lines in the house
collect waste water for
conveyance to the septic
•Roof vents and the traps
under sinks, tubs, showers,
toilets and wall/floor drains
prevent sewer gas from
entering the house.
                                Main Sewer Pipe
                Septic Tank
• All household wastewater systems will have a
  septic tank
• Microbial action digests solid wastes
• Liquids flow through tank to disposal area
• Tank size
  – 1000 gallon liquid capacity (4-BR house or less)
  – Add 250 gallons per additional bedroom
    Typical Septic Tank Installation
             Two-Chamber Tank


 Wastewater Piping Materials
• Water-tight Sewer Conveyance Lines
  –   Cast iron
  –   PVC (Sch. 40 is preferred weight)
  –   Transite (asbestos-cement)
  –   Orangeburg (paper-tar product: old houses)
• Drain Field Lines
  – Perforated PVC
  – Polyethylene infiltration chambers
  – Clay tile (old houses)
Effluent Disposal Area Options
• Absorption field
  – Absorption trenches
  – Infiltration chambers
  – ET/Absorption trenches
• Lagoons
• Aerobic systems
• Authorized alternative systems
Subsurface Absorption Field Approval
 • Percolation Test
   – 3 test holes in drainage area perc at a rate of
     60 min/inch of water or faster
 • Soil Profile Description
   – 3 test holes without any of the following:
      •   (1) impervious material (bedrock, clay pan)
      •   (2) water saturated soil (discoloration)
      •   (3) loamy coarse sand or coarser soil, or
      •   (4) sandy clay or finer soil
The size and type of waste water disposal system
is very dependent on the soil at the building site.
Even before a percolation test or soil profile
evaluation you can get an idea of site suitability
from the county soil survey.
Cross-Section of Subsurface Absorption Trench

 8-ft minimum distance to
 center of next trench           Perforated Pipe
150’ MAX.
Lateral lines following the slope contour

           150’ max. length
Infiltration Chambers
      • Polyethylene infiltration
      chamber has 100% open
      volume vs. 50% for gravel-
      filled absorption trench

       • Corrugated design gives
       strength to support ground
       traffic over its 2-ft width

        • Chamber cost per unit
        length is approximately
        equal to unit cost of
        perforated PVC pipe, plus
        gravel and installation
 ET/Absorption Trench System
• Used when soil percolation rate is too slow
  for ordinary subsurface absorption trenches
• Uses evapotranspiration (ET) of grasses plus
  soil absorption to dispose wastewater
• Plant a mix of cool and warm season grasses
  for year-round ET
   Cross-Section of ET/Absorption Trench
Cool-Warm Season Grass Mixture

                                 Perforated Pipe
• Used when soil percolation rate is too
  slow for soil absorption systems
• Require 2 ½ acre minimum lot size
• Fencing required around the lagoon
• Size based on house size, and rainfall and
  evaporation of geographic zone
• Must retain all wastewater (no overflow)
        Typical Lagoon Installation
- 2.5 acre minimum lot size required
- 4-ft high fence required
- lagoon size based on house size and local rainfall

 4 ft
                                    1       1 ft min.
             7 ft

                        5 ft max.

         Concrete Pad
Location & Lagoon Size

The required size of
total retention waste
water lagoons (because
of their annual
hydraulic balance)
makes them less
desirable the farther
east you build in
           Aerobic Systems
• Used to treat septic tank effluent where
  subsurface disposal is not possible
• Bubbling air through effluent supports
  aerobic bacteria for further digestion
• Exposure to oxygen kills most pathogens
• Chlorination allows surface land application
  of wastewater through sprinklers
       Onsite Aerobic Treatment System
Onsite aerobic treatment systems treat septic tank
effluent further by aerobic digestion, chlorination to
kill pathogens, and surface application through a
spray head sprinkler system.

   (Septic Tank)
  SEPTIC TANK                              WASTEWATER
                                           TO CHLORINATOR
                                           & SPRINKLERS


Typical Aeration Chamber of Aerobic Treatment System
Stack-Feed Contact
Tablet Chlorinator
              Chlorine Tablet
              Feed Tubes

                                Effluent Outlet

     Effluent Inlet

   Pump Chamber and             Spray Heads
Surface Application System
              Access Hatch

               Pump Control &
               Alarm Floats
Finding Waste Water System Components
• Waste water components are normally downhill
  from the house (gravity flow)
• Septic tank can be no less than 5 feet, and is
  normally no more than 50 feet from house
• Two-way sanitary sewer clean-outs located:
  – Within 5 feet of the house
  – Within 5 feet of every bend greater than 45º
  – Every 100 feet of straight sewer line
• Grass over septic tank may be brown in summer
• Grass over drain field will be greener in summer
Locating Waste Water System Components

    Clean-outs on main sewer line
Locating Waste Water System Components

    2 1/2-inch roof vent on branch line

         4-inch roof vent on main sewer line

             Sewer system roof vents
     Locating Waste Water System Components

Largest roof vent on main sewer line

 Clean-outs on main sewer line exiting house
Regular green stripes in a dry
  lawn are the lateral lines
          Household Water Use
• Typical Usage: 50-100 gallons/person-day
  –   Clothes washer:   30-50 gallons/load
  –   Dishwasher:        7-15 gallons/load
  –   Garbage Disposal: 4 - 6 gallons/day
  –   Shower/Bathtub: 25-60 gallons/use
  –   Ordinary toilet:   1.6 - 5 gallons/flush
  –   Water softener: 50-100 gallons/regeneration
       Septic System Additives
       Biological          Chemical
•   Bacteria        •   Acids
•   Yeast           •   Bases
•   Enzymes         •   Organic Solvents
•   Combination     •   Flocculants
        Biological Additives
• Will not eliminate need for tank pumping
• 20% of sludge is inorganic (indigestible)
• Billions of bacteria live in septic tanks--
  a few million more have little effect
• If natural bacteria have been killed,
  added bacteria will die also
• Normal population is restored in 30-60
  hours even if 99.99% has been killed
Maximum Safe Levels of Cleaners
  (Single dose in 1000-gallon septic tank)
• Bleach (5.25% Cl):           1.3 gallons
• Cleansers/Disinfectants:     2.5 gallons
• Drain Cleaners:              0.65 ounces
        Chemical Additives
Strong Acids and Bases
• Disrupt normal tank biological activity
• Harm soil structure in drain field

Organic Solvents
• Clean thin layers of sewer line build-up
• Contaminate ground water
    Annual Cost of Additives
   Amherst, MA Retailers Study - 1989
   (using manufacturer’s recommended rates)

• Biological (11):    $19.75/yr
• Solvents (3):       $78.00/yr
• Acid/Base (8):      $13.48/yr
  Annualized Pumping Cost
     (USPHS Pumping Frequency Estimate)
 $150 Pumping Cost for 1000-gal tank
Family Size   Pumping Freq.     Annual Cost
    2             20 yrs          $ 7.50/yr
    3             12 yrs          $12.50/yr
    4               8 yrs         $18.75/yr
    5               6 yrs         $25.00/yr
    6               4 yrs         $37.50/yr
      Septic System Additives
• Biological additives are harmless but of little use
• Chemical additives can damage septic system
  and contaminate ground water
• Don’t use if active ingredients are unspecified
• Annualized cost of additives is about the same as
  for tank pumping on recommended schedule
• “These products make a lot of money for the
  people that sell them.”
 Waste Water System Failures
           Common Causes
• Hydraulic overloading (too much water)
• Solids migration to drain field
  – Failure to pump tank on schedule
  – Baffle failure
• Root intrusion into sewer lines
• Traffic damage to drain field
• Garbage disposal overuse
 Reducing Hydraulic Loading
• Equipment Adjustments
  – Low flow toilets (1.6 gpf and 0.6 gpf)
  – Water-saving showerheads
  – Front-loading washing machines
• Lifestyle Adjustments
  –   Shower vs. bath
  –   Distribute laundry loads throughout week
  –   Distribute bathing morning & evening
  –   Full loads only for washer & dishwasher
               Root Damage
• Plant no trees or shrubs near sewer lines
• Copper sulfate to kill tree/shrub roots
  – Treatment is not toxic to plants
  – Once intruding roots are killed, absorption ends
  – Add ½ cup of crystals to distribution box or to
    cleanout downstream from septic tank
  – If added through toilet, 2 pounds of crystals are
    needed (not harmful to tank bacteria)
• See OSU CR-6428 for more information
           Traffic Damage
• No vehicle parking over drain field
• No vehicle traffic except lawn mowers
• No traffic at all if ground is saturated
        Solids & Drain Fields
• Solids must be retained in septic tank
• Baffles should be inspected when tank is
  inspected or pumped
• Use of additives that “liquefy” sludge and
  scum can lead drain field failure
• Septic tanks: like fuses in electrical wiring
  (failure in controlled location; cheap to fix)
         Garbage Disposals
• Add to hydraulic load (running water)
• Add to solids (more frequent pumping)
• Poorer digestion environment
  – (Carbon:Nitrogen ratio is more unfavorable)
Water Softeners & Septic Systems
• Salt does not affect septic tank functioning
• Added hydraulic load (regeneration water)
  – Use water meter or sensor controlled
    regeneration rather than time clock alone
• Added sodium can affect marginal drain
  fields (dispersal of clays slows perc rate)
  – Use potassium chloride (KCl) salt if a problem
MWPS-24                  Home*A*Syst     OK DEQ Ch. 641
Onsite Domestic Sewage    Worksheet #3
Disposal Handbook

 On-Site Wastewater System Resources
If you don’t maintain your on-site wastewater system, it
will demand your attention when it is most inconvenient.

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