Post on 31-Jan-2016
description
Tertiary Treatment:Tertiary Treatment:Nutrient Removal, Solids Removal, and Nutrient Removal, Solids Removal, and
DisinfectionDisinfection
Treated Wastewater Effluent Treated Wastewater Effluent Contains…Contains…
BODBOD (biochemical oxygen demand)(biochemical oxygen demand)• Carbon matter, depletes O2, causes biomat growthCarbon matter, depletes O2, causes biomat growth
TSSTSS (total suspended solids)(total suspended solids)• Depletes O2Depletes O2
NH3NH3 (ammonia)(ammonia)• Toxic to fish, depletes O2, a nutrient that promotes biol. growthToxic to fish, depletes O2, a nutrient that promotes biol. growth
NO3NO3 (nitrate)(nitrate)• Toxic to babies, drinking water regulated, a nutrientToxic to babies, drinking water regulated, a nutrient
TPTP (total phosphorus)(total phosphorus)• A nutrientA nutrient
Pathogens Pathogens (bacteria/viruses)(bacteria/viruses)• Disease causingDisease causing
First, We Must UnderstandFirst, We Must Understand
Wastewater AssimilationWastewater Assimilation A site’s ability to handle the amount of liquid or A site’s ability to handle the amount of liquid or
the amount of pollutants without causing a public the amount of pollutants without causing a public health or environmental health concernhealth or environmental health concern
In-groundIn-ground or or In-stream In-stream dischargedischarge
Sometimes, high-quality effluent is necessarySometimes, high-quality effluent is necessary• Low BODLow BOD• Low fecal coliformLow fecal coliform• Low nutrients (Nitrogen and Phosphorus)Low nutrients (Nitrogen and Phosphorus)
Protection of sensitive waterbodies, nearby…Protection of sensitive waterbodies, nearby…• Or drinking water supplies (groundwater & wells)Or drinking water supplies (groundwater & wells)
““Discharge” PermitsDischarge” Permits In-ground dispersalIn-ground dispersal
• ADEM for flows of 10,000 gpd +ADEM for flows of 10,000 gpd + UIC Permit (underground injection control)UIC Permit (underground injection control)
• Specifies a certain effluent quantity and qualitySpecifies a certain effluent quantity and quality • BOD, TSS and groundwater monitoring for NOBOD, TSS and groundwater monitoring for NO33
• ADPH for smaller systemsADPH for smaller systems
Surface dispersalSurface dispersal• Stream DischargeStream Discharge
NPDES PermitNPDES Permit (specifies BOD, TSS, NH(specifies BOD, TSS, NH33, NO, NO33, TP, etc.), TP, etc.) Disinfection RequiredDisinfection Required
• Spray IrrigationSpray Irrigation NPDES PermitNPDES Permit 7-10 day holding pond required7-10 day holding pond required Disinfection RequiredDisinfection Required
Why is tertiary treatment needed?Why is tertiary treatment needed?
To better protect public health and To better protect public health and environmentenvironment
To provide additional treatment when soils To provide additional treatment when soils or receiving waters cannotor receiving waters cannot
Biological Nitrogen RemovalBiological Nitrogen Removal
Uptake into biological cell massUptake into biological cell mass
Nitrification Nitrification (conversion to Nitrate)(conversion to Nitrate)
Denitrification Denitrification (conversion to N(conversion to N22 gas) gas)
Biological NitrificationBiological Nitrification
Conversion of Ammonia to Nitrite Conversion of Ammonia to Nitrite (Nitrosomonas)(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 NHFor each mg of NH44++ converted… converted…
3.96 mg of O3.96 mg of O22 are utilized are utilized (Need Oxygen)(Need Oxygen)0.31 mg of new cells are formed0.31 mg of new cells are formed
7.01 mg of alkalinity are removed7.01 mg of alkalinity are removed
Nitrification (cont.)Nitrification (cont.)
Nitrifying bacteria are Nitrifying bacteria are sensitivesensitive and and susceptible to a variety of conditions.susceptible to a variety of conditions.
The following factors affect nitrification:The following factors affect nitrification:• Conc of NHConc of NH44
++ and NO and NO22--
• BOD/TKN ratio BOD/TKN ratio (BOD should be (BOD should be gone/removed)gone/removed)
• Dissolved oxygen conc Dissolved oxygen conc (need oxygen)(need oxygen)• TemperatureTemperature• pH (7.5 to 8.6)pH (7.5 to 8.6)
Nitrification ProcessesNitrification Processes
Suspended Growth Separate Stage Nitrification
Single State Nitrification
Nitrification ProcessesNitrification Processes
Attached Growth
Attached Growth Nitrification following Act. Sludge
Biological DenitrificationBiological Denitrification
A modification of aerobic pathways A modification of aerobic pathways (no oxygen)(no oxygen)• Same bacteria that consume carbon material aerobicallySame bacteria that consume carbon material aerobically
Denitrifying bacteria obtain energy from the Denitrifying bacteria obtain energy from the conversion of conversion of NONO33
-- to N to N22 gas gas, but, but
require a carbon sourcerequire a carbon source
NONO33-- + CH + CH33OH + HOH + H22COCO33 C C55HH77OO22N + N + NN22 + H + H22O + HCOO + HCO33
--
Organic matter Cell mass
DenitrificationDenitrification
Need low (no) oxygen (< 1 mg/L)Need low (no) oxygen (< 1 mg/L) Need carbon source (BOD in Wastewater)Need carbon source (BOD in Wastewater) Neutral pH Neutral pH (pH 7)(pH 7) Conc of nitrateConc of nitrate
Denitrification (cont.)Denitrification (cont.)
Separate denitrification reactorSeparate denitrification reactor
oror Combined Carbon Oxidation-Combined Carbon Oxidation-
nitrification-denitrification reactornitrification-denitrification reactor• A series of alternating aerobic and anoxic A series of alternating aerobic and anoxic
stagesstages• Reduces the amount of air neededReduces the amount of air needed• No need for supplemental carbon sourceNo need for supplemental carbon source
Combined Nitrification/DenitrificationCombined Nitrification/Denitrification(note alternating regions of aerobic and anoxic)(note alternating regions of aerobic and anoxic)
Phosphorus RemovalPhosphorus Removal
Chemical PrecipitationChemical Precipitation• Calcium (lime) addition at high pH (>10)Calcium (lime) addition at high pH (>10)
Reacts with alkalinityReacts with alkalinity
• Alum Alum ((Aluminum Sulfate)Aluminum Sulfate) precipitation precipitation• Iron precipitationIron precipitation
DisinfectionDisinfection
Selective destruction of disease-Selective destruction of disease-causing organismscausing organisms
1.1. ChlorineChlorine
2.2. UV LightUV Light
3.3. Ozone (gas)Ozone (gas)
Chlorine DisinfectionChlorine Disinfection
1.1. Liquid chlorine Liquid chlorine
2.2. Sodium hypochlorite (tablets) Sodium hypochlorite (tablets)
Note: not allowed to discharge chlorineNote: not allowed to discharge chlorine(it must be removed after disinfection)(it must be removed after disinfection)
* * chlorine removed with either…chlorine removed with either…
a. sulfur dioxidea. sulfur dioxide
b. sodium bisulfiteb. sodium bisulfite
Tablet ChlorinatorTablet Chlorinator(Calcium Hypochlorite)(Calcium Hypochlorite)
Chlorine DisinfectionChlorine Disinfection
To be effective…To be effective…• Chlorine concentrationChlorine concentration• Contact timeContact time• Proper mixingProper mixing• TemperatureTemperature• Number and type of organismsNumber and type of organisms
Chlorine DoseChlorine Dose
UV DisinfectionUV Disinfection
UV LightUV Light• Specific wavelengths have biocidal Specific wavelengths have biocidal
properties (~254 nm)properties (~254 nm)• Quartz, mercury-vapor lampsQuartz, mercury-vapor lamps• Cleaning required Cleaning required • No residualNo residual
UV DisinfectionUV Disinfectiona specific wavelength of lighta specific wavelength of light
UV DisinfectionUV Disinfection
Ozone DisinfectionOzone Disinfection
OO33 a gas, must be generated on-site a gas, must be generated on-site
Bubbled into a basin Bubbled into a basin (or pipeline)(or pipeline) with treated with treated effluenteffluent
Great disinfectant!Great disinfectant!
No residual…ozone degrades to oxygen, ONo residual…ozone degrades to oxygen, O22
Costs More, Need equipment and electricityCosts More, Need equipment and electricity
Ozone DisinfectionOzone Disinfection
Flow DiagramOzone Generation