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CHEE 370 Waste Treatment Processes Lecture #5-Wastewater Treatment Process.

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Presentation on theme: "CHEE 370 Waste Treatment Processes Lecture #5-Wastewater Treatment Process."— Presentation transcript:

1 CHEE 370 Waste Treatment Processes Lecture #5-Wastewater Treatment Process

2 Review: WW Characterization Solids content TS, TSS, TDS, VS (organic), FS (inorganic) Organic content BOD, COD, TOC, ThOD Micro-organisms Total coliform, fecal coliform Toxicity Acute toxicity (LC 50 ), Chronic toxicity Nutrients TKN, NH 3, TP, ortho-phosphate Flowrates Hydraulic flowrates (peak and min), Loadings

3 Municipal WW Effluent (MWWE) Guidelines and Regulations

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5 Management of MWWE More than 3500 WWTP in Canada No real “standard” Treatment strategies range from no treatment to state of the art In many systems, during wet weather the combined sewer outflow (CSO) of the sewer system and storm water system often exceeds total hydraulic capacity of the plant Kingston has this particular problem!!! Problems with aging infrastructure

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9 Data for 1999

10 Legislation Municipalities are responsible for WW management Provincial governments are responsible for regulating the operation of WWTP There is currently no federal legislation on municipal WW effluent Fisheries Act Canadian Environmental Protection Act, 1999

11 Proposed Canada-wide Strategy for the Management of MWWE Drafted Oct. 2007

12 Facility Size Categories Flow (Q) [m 3 /d] Very SmallQ ≤ 500 Small500 < Q ≤ 2500 Medium2500 < Q ≤ Large17500 < Q ≤ Very LargeQ > 50000

13 National Performance Standards Effluent from all treatment plants must satisfy: CBOD 5 ≤ 25 mg/L TSS ≤ 25 mg/L Total Residual Chlorine (TRC) ≤ 0.02 mg/L Ammonia: Based on acute and chronic toxicity TSS and CBOD 5 values can be averaged: Very Small - Medium WWTP: Quarterly Large or Very Large WWTP: Monthly Consider changes in TSS and BOD 5 as a function of time of day and season!

14 Review: Toxicity Testing - Bioassays LC 50 : Median lethal concentration for 50% of the organisms The diluted concentration of the wastewater that will kill 50% of the test population in a fixed time period NOEC: No Observed Effect Concentration The highest concentration of diluted wastewater that has no observable effect on the test organisms ACUTE TOXICITY CHRONIC TOXICITY

15 Acute Testing Requirement Rainbow Trout Test Swim-up fry or fingerling ( g) 96-h single concentration test (100% and control) 10 fish/test Three replicates=> To accommodate death arising from natural causes! Daphnia Magna Test “Water flea” - small freshwater crustacean 48-h single concentration test (100% and control) 30 daphnids/test Three replicates

16 Daphnid

17 Acute Toxicity Testing Failure = when the effluent at 100% concentration kills more than 50% of the test organisms in the specified time period  LC 50 = 100%

18 Acute Toxicity Testing What happens if a test fails? “Toxicity Reduction Evaluation” (TRE) Try to identify the source of the toxicity Calculate the LC 50 using a dilution series of the effluent within 5 days of a failed test Minimum 5 test concentrations plus a control Typical range: 100x (full strength) down to 1x (dilute) of the effluent

19 Acute Toxicity Units (TU A ) TU A = 100/LC 50 “Effluent Discharge Objectives” (EDO) EDO = 1 TU A Measured “ At the end of the pipe”  LC 50 = 100%

20 Chronic Toxicity Testing considers the local environment Requirements are influenced by site-specific factors Type of waterway (river, stream, lake, etc.) Spawning location, recreational facilities etc. Effects on growth, reproduction, and swimming Fathead minnow larvae and Ceriodaphnia dubia 7-day test is typical

21 Chronic Toxicity TU C = 100/NOEC EDO = 1TU C for diluted sample Measured at “the end of the mixing zone” Not at wastewater discharge point from plant! Dilution factor based on the type of receiving waterway Rivers and streams - Max 1:100 Dilution Lakes, reservoirs, enclosed bays - Max 1:10 Dilution  NOEC = 100% for diluted sample

22 Monitoring Frequencies Facility Size CBOD 5, TSS, Coliform, TKN, TP, NH 3 TRCAcute Toxicity Chronic Toxicity Very SmallMonthlyDailyn/a SmallMonthlyDailyQuarterly MediumEvery 2 weeksDailyQuarterly LargeWeekly2x / dayMonthly Very LargeDaily (5-7 days/week) 3x / dayMonthly Flowrates also monitored throughout the day

23 Guidelines and Regulations: Other Contaminants

24 Federal Discharge Guidelines Fecal Coliforms: 100 colonies per 100 mL Total Coliforms: 1000 colonies per 100 mL TP: 1.0 mg-P/L Ammonia: 1 mg/L Nitrate: 10 mg/L pH: 6 to 9 Temperature - not to alter the ambient water temperature by more than 1 ºC

25 Federal Discharge Guidelines Cadmium: mg/mL Copper: 0.2 mg/mL Lead: 0 mg/mL (detection limit) Mercury: 0 mg/mL (detection limit) Nickel: 0.3 mg/mL Zinc: 0.5 mg/mL PCBs and dioxins: 0 mg/mL (detection limit) PCBs are serious carcinogens!

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28 Overview of Unit Operations in WW Treatment

29 Typical Municipal WW TSS: 220 mg/L VSS: 165 mg/L BOD 5 : 220 mg/L COD: 500 mg/L TKN: 40 mg-N/L Ammonia: 25 mg-N/L TP: 8 mg-P/L Ortho-phosphate: 5 mg-P/L

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31 Types of Reactors Used in WW Treatment Batch Continuously stirred tank reactor (CSTR) CSTR with recycle Plug flow Plug flow with recycle CSTR in series Fluidized-bed Packed-bed

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