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A Study of Ammonia and Nitrite Levels in Iowa Ground Water

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A Study of Ammonia and Nitrite Levels in Iowa Ground Water Powered By Docstoc
					A Study of Ammonia and
  Nitrite Levels in Iowa
      Ground Water

       Jennifer Simons
     Iowa Department of
      Natural Resources
                   Overview
   Ammonia in ground water? So what?!
   IDNR’s statewide study
       Phase I
       Phase II
   Conclusions?
         Ammonia in Ground Water?
               So What?!

   Not a regulated SDWA contaminant, but…
   Ammonia converts to nitrite in the
    presence of oxygen and Nitrosomonas
   Nitrite IS a regulated SDWA contaminant,
    with an MCL of 1 mg/L as N
          Ammonia in Ground Water?
                So What?!
   In the presence of oxygen and
    Nitrobacter, nitrite will convert to nitrate
   Nitrite is an acute contaminant, with
    health effects similar to those of nitrate
   Nitrite only has a one-time sampling
    requirement
   Ammonia concentrations >1 mg/L could
    lead to a nitrite MCL
      Chemistry Review

Protein (organic N) + bacteria       NH3

             bacteria
2NH3 + 3O2              2NO2- + 2H+ + 2H2O

             bacteria
2NO2- + O2              2NO3-
    Factors Contributing to the
    Ammonia-Nitrite Conversion
   Water quality factors*
       Optimal pH 7.2-8.5
       Optimal temperature 72-86F
       Nitrification consumes DO
       Natural organic matter seems to add to the
        potential for nitrification, but this is not well
        understood
       Nitrifying bacteria are found almost
        everywhere
    *Taken from Journal AWWA, July 1996
    Factors Contributing to the
    Ammonia-Nitrite Conversion
   Physical and Operational Factors*
       Long detention time in the distribution
        system increases potential for nitrification
       Poor circulation in storage reservoirs
        contributes to nitrification
       Sediment, biofilms and tubercles may exert
        chlorine demand and allow nitrifying
        bacteria to grow in the distribution system
    *Taken from Journal AWWA, July 1996
  Factors in the Biological
        Conversion
Factor        Nitrosomonas Nitrobacter
pH            5.8 – 9.5      5.7 – 10.2
Optimum pH    7.5 – 8.0      7.6 – 7.8
Temperature   5 – 30 C       5 – 40 C
Optimum Temp 30 C            28 C
Chlorine      Less sensitive Very sensitive
Ammonia       Consume        Very sensitive
    IDNR’s Statewide Study
   Studies by USGS and experiences with
    water systems have shown that
    ammonia is present in groundwater
    throughout Iowa
   Objectives
       Investigate occurrence and concentration
        of ammonia, nitrite and nitrate in GW
       Evaluate the risk for adverse health effects
        in surrounding communities
    IDNR’s Statewide Study
   Phase I
       230 municipal wells representing each
        major aquifer
       Single well systems or multiple well
        systems finished in same formation
       Samples analyzed for pH, temperature,
        ammonia, nitrite, nitrate, and perchlorate
                 Phase I
   233 samples collected
   Ammonia Results
       114 non-detects
       68 were <1 mg/L
       31 were between 1-2.5 mg/L
       16 were between 2.5-5 mg/L
       4 were >5 mg/L
   Nitrite was detected in two samples
                  Phase I
   Of 51 samples with NH3 > 1 mg/L
       16 used drift aquifers
       8 used the Silurian Devonian aquifer
       8 used the Dakota Sandstone aquifer
       5 used the Mississippian aquifer
       5 used the Cambrian Ordovician aquifer
       4 used alluvial aquifers
       3 used the Ordovician aquifer
       2 used the Pennsylvanian aquifer
            Phase I
      Ammonia Concentrations

> 5 mg/L
2.5-5 mg/L
1-2.5 mg/L
<1 mg/L
Non-detect
      Phase I
Ammonia Concentrations
      IDNR’s Statewide Study
             Phase II
   Looked at wells with ammonia >1 mg/L in
    Phase I
   Chose 30 of these systems with a variety
    of treatment schemes for Phase II
    sampling
   Sampled at each point of treatment train
    for nitrate, nitrite, ammonia, DO, pH,
    HPC, nitrifying bacteria, and field temp
Preliminary Phase II Results
           Case 1
   System serving population of 1030,
    located in north-central Iowa
   Phase I ammonia level was 2.6 mg/L
   System consists of two Silurian
    Devonian wells, aeration, pressure
    filtration, softening, fluoridation,
    chlorination, and polyphosphate
    addition, with a 150,000 gallon EST
   Preliminary Phase II Results
              Case 1
2 Silurian Devonian Wells              Post Aeration
       NH3 = 2.6                             NH3 = 2.5
       NO2 <0.02                            NO2 <0.02
       NO3 <0.1                              NO3 <0.1
    HPC = 10 CFU/ml                      HPC <10 CFU/ml
      Nitrifiers = a               Nitrifiers = ~1000 CFU/ml

                       Post Sand Filter
                           NH3 = 2.3
                          NO2 = 0.05
                           NO3 <0.1
                       HPC <10 CFU/ml
                 Nitrifiers = ~1,000 CFU/ml
   Preliminary Phase II Results
              Case 1

    Post Softener             Distribution System
          NH3 = 1.8                      NH3 <0.1
         NO2 = 0.04                     NO2 = 0.37
          NO3 <0.1                      NO3 = 1.3
     HPC = 110 CFU/ml               HPC = 100 CFU/ml
Nitrifiers = ~1,000 CFU/ml   Nitrifiers = ~100,000 CFU/ml
Preliminary Phase II Results
           Case 2
   System serving population of 780 in
    northwest Iowa
   Phase I ammonia level was 1.7 mg/L
   System consists of wells in a drift
    aquifer, aeration, detention, sand
    filtration, fluoridation, phosphate
    addition, gas chlorination, and a
    250,000 EST
Preliminary Phase II Results
           Case 2
Wells in Drift Aquifer                  Post Aeration
     NH3 = 1.7                             NH3 = 1.8
     NO2 <0.02                             NO2 <0.02
     NO3 <0.1                              NO3 <0.1
    HPC <10 CFU                          HPC = 10 CFU
    Nitrifiers = a                        Nitrifiers = a

                     Post Detention
                        NH3 = 1.7
                        NO2 <0.02
                        NO3 <0.1
                      HPC = 10 CFU
                       Nitrifiers = a
Preliminary Phase II Results
           Case 2
  Post Filtration               Post Chlorination
      NH3 = 0.3                          NH3 = 0.2
     NO2 = 0.42                          NO2 <0.02
      NO3 = 1.0                          NO3 = 1.1
   HPC <10 CFU                         HPC = 40 CFU
Nitrifiers = ~10,000                    Nitrifiers = a

               Distribution System
                       NH3 <0.1
                       NO2 <0.02
                       NO3 = 1.4
                    HPC = 5,400 CFU
                      Nitrifiers = a
Summary of Case Study Results
    Every situation is different!

    Raw water ammonia at a concentration
     >1 mg/L could lead to a nitrite MCL
     violation, given the right conditions
Questions We Hope to Answer
   Are certain types of treatment systems
    more prone to nitrite exceedances when
    ammonia is present in the raw water?

   Are expected health outcomes being
    seen in communities with high
    ammonia/nitrite/nitrate levels?
Questions We Hope to Answer
   Should we consider increasing the nitrite
    monitoring frequency or changing the
    sampling point to protect public health?
   Should we consider requiring all systems
    to sample for ammonia?
   Should we require systems with raw
    water ammonia concentrations >1 mg/L
    to perform additional sampling?
Thank you for your attention!




    Questions?
        515/281-5130
        jennifer.simons@dnr.state.ia.us

				
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posted:10/5/2012
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