CEE 371 Water and Wastewater Systems

Transcription

1 Updated: 22 November 2009 CEE 371 Water and Wastewater Systems Print version Lecture #26 Atkins WTP: Plant Tour Reading: Handout (Dumais et al., 1994) David Reckhow CEE 371 L#26 1 Bus to Atkins WTP Pick up bus at 8:50AM (Friday November 6 th ) back of Elab II If you need to drive yourself, see following maps and directions Take N or E. Pleasant up to Pine St. Right on Pine Left on Bridge Right on Market Hill Road Right to Atkins WTP Parking lot David Reckhow CEE 371 L#26 2 Lecture #18 Dave Reckhow 1

2 Route Route to Atkins WTP David Reckhow CEE 371 L#26 3 Close-up of driveway Terrain from Google earth Park Here David Reckhow CEE 371 L#26 4 Lecture #18 Dave Reckhow 2

3 Amherst, MA, Drinking Water System Atkins Water Treatment Plant Source: Atkins Reservoir Design Flow: 1.5 million gallons per day On-line: February 1994 Treatment: Coagulation (addition of caustic soda and polymer) Ozonation (2 locations; raw & filtered) Trident upflow clarification Filtration Disinfection For more on the plant see paper by Dumais et al. Pre-Trident Ozonation control of taste and odor, color removal CT credits achieved 25 /L dd d 2.5 mg/l ozone added 4 chambers in series Lecture #18 Dave Reckhow 3

4 Amherst Ozone Contactors Pre and Post contactors are identical Four chambers Under/over baffled David Reckhow CEE 371 L#13 7 Pre-Trident Chemical Addition coagulant addition (alum and cationic polymer) ph adjustment for optimization of Trident process Lecture #18 Dave Reckhow 4

5 Trident Filtration Process 3 factory fabricated steel tanks, 0.75 MGD each buoyant plastic media in upflow clarifier conventional media filtration (anthracite coal and sand) Trident Clarification/Filtration Unit TR 420A David Reckhow CEE 371 L#17 10 Lecture #18 Dave Reckhow 5

6 Adsorption Clarifier Media AC Media Technical Details: Buoyant Media Specific gravity slightly < 1.0 Allows for complete fluidization Effective size ~2.5 mm Rolled and scarified media Lasts for life of plant No maintenance required Operation: Filtration Lecture #18 Dave Reckhow 6

7 Operation: Clarifier Flush AC typically cleans 2 to 4 times per every filter backwash Operation: Filter Backwash Lecture #18 Dave Reckhow 7

8 Post-Trident Ozonation redundancy for pre-trident ozonation removal of dissolved organic carbon 1.5 mg/l ozone added Identical to pre-ozone contactor Granular Activated Carbon (GAC) Adsorption reduced taste and odor, chlorination byproducts improved removal of DOC reduced d chlorine demand, d potential ti for regrowth Lecture #18 Dave Reckhow 8

9 Chlorine / Ammonia Addition necessary to keep residuals in system ammonia is optional (chloramines) Chlorine Contact Tank 22.5 ft depth, L/W ratio = 14 with 5 redwood perforated baffles Backup for CT requirement Lecture #18 Dave Reckhow 9

10 Caustic Soda Addition (raise ph) corrosion control in distribution system Ammonia Addition (convert chlorine to chloramines) control of trihalomethanes, other disinfectant residuals Clearwell Storage Tanks additional disinfectant contact time flow equalization and backwash control 2 tanks with 250, gallon capacity each Lecture #18 Dave Reckhow 10

11 Amherst O 3 Contactor II C/C Atkins WTP, Ozone Contactor Fluoride Data Ideal PFR Ideal CSTR C C 0 1 e = Fluoride Tracer test Step t=0 2.4 mg/l Added to inlet Measure F - at outlet vs time Q=1000 gpm V=22,980 gal C 0 =2.4 mg/l David Reckhow CEE 371 L#13 21 Time (min) t t R Data from :Teefy, 1996 [AWWARF Report] Amherst O 3 Contactor III Calculation of t min or 65% of t R 0.3 Atkins WTP, Ozone Contactor C/C 0 Fluoride Data Ideal PFR 0.2 Ideal CSTR 0.1 C/C 0 =10% Data from :Teefy, 1996 [AWWARF Report] 2.5 min 14 min 23 min David Reckhow CEE 371 L#13 22 Time (min) Lecture #18 Dave Reckhow 11

12 Ct values for Viruses For Viruses at various temperatures ph 6-9 H&H Table 7-5, pg 245 David Reckhow CEE 371 L#13 23 Amherst O 3 Contactor IV Use of t 10 for disinfection compliance Conventional treatment requires 2 log virus inactivation by disinfection For ozone 0.9 mg/l min is worst case (0.5 o C, in H&H table 7-5) With a if t 10 = 14 min, then we need to have mg/l ozone residual at outlet of tank C ( Ct) 0.9 min mg required L min = = = t10 14 min mg L David Reckhow CEE 371 L#13 24 Lecture #18 Dave Reckhow 12

13 End To next lecture David Reckhow CEE 371 L#26 25 Lecture #18 Dave Reckhow 13