tertiary treatment nutrient removal solids removal and disinfection
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Tertiary Treatment: Nutrient Removal, Solids Removal, and Disinfection. Treated Wastewater Effluent Contains…. BOD (biochemical oxygen demand) Carbon matter, depletes O2, causes biomat growth TSS (total suspended solids) Depletes O2 NH3 (ammonia)

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Presentation Transcript
treated wastewater effluent contains
Treated Wastewater Effluent Contains…
  • BOD(biochemical oxygen demand)
    • Carbon matter, depletes O2, causes biomat growth
  • TSS(total suspended solids)
    • Depletes O2
  • NH3(ammonia)
    • Toxic to fish, depletes O2, a nutrient that promotes biol. growth
  • NO3(nitrate)
    • Toxic to babies, drinking water regulated, a nutrient
  • TP(total phosphorus)
    • A nutrient
  • Pathogens (bacteria/viruses)
    • Disease causing
first we must understand wastewater assimilation
First, We Must UnderstandWastewater Assimilation
  • A site’s ability to handle the amount of liquid or the amount of pollutants without causing a public health or environmental health concern
  • In-ground or In-stream discharge
  • Sometimes, high-quality effluent is necessary
    • Low BOD
    • Low fecal coliform
    • Low nutrients (Nitrogen and Phosphorus)
  • Protection of sensitive waterbodies, nearby…
    • Or drinking water supplies (groundwater & wells)
discharge permits
“Discharge” Permits
  • In-ground dispersal
    • ADEM for flows of 10,000 gpd +
      • UIC Permit (underground injection control)
        • Specifies a certain effluent quantity and quality
        • BOD, TSS and groundwater monitoring for NO3
    • ADPH for smaller systems
  • Surface dispersal
    • Stream Discharge
      • NPDES Permit(specifies BOD, TSS, NH3, NO3, TP, etc.)
      • Disinfection Required
    • Spray Irrigation
      • NPDES Permit
      • 7-10 day holding pond required
      • Disinfection Required
why is tertiary treatment needed
Why is tertiary treatment needed?
  • To better protect public health and environment
  • To provide additional treatment when soils or receiving waters cannot
biological nitrogen removal
Biological Nitrogen Removal
  • Uptake into biological cell mass
  • Nitrification (conversion to Nitrate)
  • Denitrification (conversion to N2 gas)
biological nitrification
Biological Nitrification

Conversion of Ammonia to Nitrite (Nitrosomonas)

NH4+ + 2 O2  NO2- + 2 H+ + H2O

Conversion of Nitrite to Nitrate(Nitrobacter)

NO2- + 0.5 O2    NO3-

nitrification cont
Nitrification (cont.)
  • For each mg of NH4+ converted…

3.96 mg of O2 are utilized(Need Oxygen)

0.31 mg of new cells are formed

7.01 mg of alkalinity are removed

nitrification cont1
Nitrification (cont.)
  • Nitrifying bacteria are sensitive and susceptible to a variety of conditions.
  • The following factors affect nitrification:
    • Conc of NH4+ and NO2-
    • BOD/TKN ratio (BOD should be gone/removed)
    • Dissolved oxygen conc (need oxygen)
    • Temperature
    • pH (7.5 to 8.6)
nitrification processes
Nitrification Processes

Suspended Growth Separate Stage Nitrification

Single State Nitrification

nitrification processes1
Nitrification Processes

Attached Growth

Attached Growth Nitrification following Act. Sludge

biological denitrification
A modification of aerobic pathways (no oxygen)

Same bacteria that consume carbon material aerobically

Denitrifying bacteria obtain energy from the conversion of NO3- to N2 gas, but

require a carbon source

NO3- + CH3OH + H2CO3  C5H7O2N + N2 + H2O + HCO3-

Biological Denitrification

Cell mass

Organic matter

denitrification
Denitrification
  • Need low (no) oxygen (< 1 mg/L)
  • Need carbon source (BOD in Wastewater)
  • Neutral pH (pH 7)
  • Conc of nitrate
denitrification cont
Denitrification (cont.)
  • Separate denitrification reactor

or

  • Combined Carbon Oxidation-nitrification-denitrification reactor
    • A series of alternating aerobic and anoxic stages
    • Reduces the amount of air needed
    • No need for supplemental carbon source
phosphorus removal
Phosphorus Removal
  • Chemical Precipitation
    • Calcium (lime) addition at high pH (>10)
      • Reacts with alkalinity
    • Alum (Aluminum Sulfate) precipitation
    • Iron precipitation
disinfection
Disinfection
  • Selective destruction of disease-causing organisms
    • Chlorine
    • UV Light
    • Ozone (gas)
chlorine disinfection
Chlorine Disinfection
  • Liquid chlorine
  • Sodium hypochlorite (tablets)

Note: not allowed to discharge chlorine

(it must be removed after disinfection)

* chlorine removed with either…

a. sulfur dioxide

b. sodium bisulfite

chlorine disinfection1
Chlorine Disinfection
  • To be effective…
    • Chlorine concentration
    • Contact time
    • Proper mixing
    • Temperature
    • Number and type of organisms
uv disinfection
UV Disinfection
  • UV Light
    • Specific wavelengths have biocidal properties (~254 nm)
    • Quartz, mercury-vapor lamps
    • Cleaning required
    • No residual
ozone disinfection
Ozone Disinfection
  • O3 a gas, must be generated on-site
  • Bubbled into a basin (or pipeline) with treated effluent
  • Great disinfectant!
  • No residual…ozone degrades to oxygen, O2
  • Costs More, Need equipment and electricity
ozone disinfection1
Ozone Disinfection

Flow Diagram

Ozone Generation

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