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1 CTC 450 Review WW Systems Operations. Last Homework Will replace your lowest homework grade

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Presentation on theme: "1 CTC 450 Review WW Systems Operations. Last Homework Will replace your lowest homework grade"— Presentation transcript:

1 1 CTC 450 Review WW Systems Operations

2 Last Homework Will replace your lowest homework grade How significant are wastewater treatment plants in contributing to greenhouse gasses? Due next Monday 2

3 3 Objectives Understand the basics with respect to advanced WW treatment

4 4 Two systems Advanced (tertiary and ww reclamation) Remove phosphorous Convert ammonia to nitrate (nitrification) Convert nitrate to nitrogen (denitrification) Inactivate pathogens Remove heavy metals Remove organic chemicals Remove inorganic salts Eliminate all pathogens

5 5 Limitations-Biological Treatment Doesn’t remove phosphorous or ammonia Incomplete disinfection Doesn’t remove all toxins Doesn’t remove non-biodegradable soluble chemicals

6 6 Excess Phosphorous “Fertilizes” receiving waters Causes algal blooms Depletes DO Reduces water transparency Releases foul odors Can lose “finer” fish species

7 7 Excess Nitrogen Ammonia can be toxic to fish/aquatic animals Can increase eutrophication (but usually phosphorous is limiting)

8 8 Pathogens Conventional biological treatment Up to 99.9% removal With disinfection up to 99.99% Protozoal cysts and helminth eggs are resistant

9 9 SS Removal-Advanced Granular-Media filters (similar to water treatment) Cloth Media filters Membrane filters

10 10 Pathogen Removal-Advanced Remove solids first via filtration (pathogens can be protected in the solids) Chlorination (similar to water treatment)

11 11 Toxic Substance Removal Toxic-Hazardous to aquatic life or human health Priority toxic water pollutants-over 100 Evaluating toxicity Test influent/effluent for specific substances Biomonitor-fathead minnows, water fleas

12 12 Phosphorous Removal Soluble or organic (organically bound) Conventional treatment removes 20-40% of phosphorus Example 13-1 Advanced treatments Chemical-biological Reverse osmosis

13 13 Example 13-1 (Where is the PO 4 3- ) Given the following, trace the inorganic, organic and total phosphorus through a conventional activated- sludge treatment plan. Assume: Primary clarifier removal of 35% BOD Primary clarifier removal of 50% solids w/ 0.9% phosphorous Activated sludge F/M ratio of 0.40 & 2% phosphorus in the sludge Filtrate recycles 5% of the influent phosphorus

14 14 Example 13-1 ParameterRawAfter PrimaryAfter Secondary SS24012030 BOD20013030 Inorganic N22 24 Organic N1382 Total N353026 Inorganic P443 Organic P322 Total P765

15 15 Example 13-1 (Refer to Figure 13-11) Plant Influent / Primary Influent Total P is 7 mg/l into the plant (100%) Primary influent is not the same as plant influent because of recycle of dewatered sludge filtrate Recycled P=5% so influent P=105% Total P is 7.35 mg/l into the primary

16 16 Example 13-1 (Refer to Figure 13-11) Primary Effluent (2 routes) Sludge (15%) 0.9%*120 mg/l = 1.1 mg/l 1.1/7 = 15% Effluent (90%); 7.35-1.1=6.25 mg/l total Pi=4.35 (see table; no change in inorganic P) Po=1.90 (6.25-4.35) 6.25/7 = 90%

17 17 Example 13-1 (Refer to Figure 13-11) Secondary Effluent (2 routes) Sludge (20%) From Fig 11-45 (pg 415) k=0.5 Biological sludge solids=0.5*130 mg/l=65mg/l 2% of 65 mg/l = 1.3 mg/l 1.3/7 = 20% Effluent (70%); 7.35-1.1=6.25 mg/l total Pi=3.05 (see table; inorganic P is removed) (6.25-1.3-1.9) Po=1.90 (see table; organic P is not removed) 4.95/7 = 70%

18 18 Example 13-1 (Refer to Figure 13-11) 70% of P remains in the treated WW 30% of P removed in sludge solids

19 19 Chemical-Biological Chemicals used Alum Iron Salts Chemical-Biological Chemicals added in primary clarifiers Chemicals added before secondary Chemicals added before final clarifier

20 20 Example 13-2 (Refer to Figure 13-12) Add alum to remove P Alum applied to primary tank 18% of P remains in the treated WW 82% of P removed in sludge solids

21 21 Nitrogen-Atmospheric Atmospheric Nitrogen to Organic Molecules Nitrogen-fixing bacteria (rhizobia) Live in root nodules of plants (symbiotic relationship) Legumes (beans, clover, peas, peanuts,…) Plants get nitrogen in a usable form Animals get nitrogen from eating plants Animals excrete nitrogen as a waste product, usually in the form of ammonia

22 22 Nitrogen Organic Excreted or Decomposed to ammonia Ammonia Nitrosomonas oxidize ammonia to nitrite Nitrite Nitrobacter oxidize nitrite to nitrate Nitrate Under anaerobic conditions via facultative heterotrophs, nitrates are converted to nitrogen gas (which escapes into the atmosphere) Nitrogen gas

23 New Type of Microbe Ammonia to nitrogen directly NH 4 + + NO 2 − → N 2 + 2H 2 O Anammox (anaerobic ammonium oxidation) Advantage: No oxygen needed Strangeness: anammox bugs also produce hydrazine (rocket fuel) Bugs store the hydrazine in a dense membrane structure of fused carbon rings Ref: The Invisible Kingdom, Idan Ben-Barak 23

24 24 Nitrogen in WW 40% ammonia; 60% is bound in organic matter Usually not enough oxygen is available to convert to nitrites or nitrates

25 25 Nitrogen Removal-Conventional Primary sedimentation (15% removal) Biological treatment (another 10%) Remainder is mainly in the form of ammonia unless oxidation occurs (activated sludge at low BOD loading)

26 26 Nitrogen Removal-Advanced After biological treatment: Aeration Final settling Alkalinity is reduced when nitrification takes place; lime or soda ash is added to maintain alkalinity

27 27 Nitrate removal Nitrate can pollute groundwater Denitrification converts nitrates to nitrogen gas Process is anaerobic or anoxic Process requires an organic carbon source (methanol or raw ww) Via recycle, denitrification can be placed ahead of nitrification

28 28 EBPR-Enhanced Biological Phosphorous Removal Anoxic zone (0.5 to 3 hours detention time) followed by aerobic zone (6-24 hrs) Helps remove both N and P

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