Is membrane filtration worth it?

Transcription

1 Is membrane filtration worth it? A case study of 3 municipal MBR s in Michigan and their operational experiences. Joe Hebert - Ottawa County Public Utilities 1

2 Who are these MBR s? North Kent Sewer Authority, Parcc Side Clean Water Plant 4 years Crockery Twp Clean Water Plant 6 years Traverse City Regional WWTP 8 years All of them are using the GE (Zenon) ZeeWeed 500 series membranes. What is ZeeWeed? PVDF hollow fiber membrane (outside-in pathway) 0.04 micron nominal pore size 1.9mm O.D. 0.8mm I.D. TMP range = -8 to 8 psi 2

3 Background Start-up was October 30, 2008 Membranes installed for 6 MGD (40-500D cassettes w/ 60 modules per cassette) Average flow of 3.5 MGD (58% of design) Permit Limits (mo. average) 0.5 mg/l NH3 4 mg/l CBOD 20 mg/l TSS 1 mg/l Phosphorus 200 cts fecal Coliform 3

4 Operations Biological phosphorus removal Sodium 0.5:1 MLSS 4,500 mg/l Flux rate y 7 gf 2 d (designed 9.7 gf 2 d) Maintenance cleaning weekly (alternating hypochlorite and citric acid) Recovery cleaning twice yearly (hypochlorite and citric acid) Membrane performance same as new Operational Costs Electric - $1,200 day (70% secondary) Sodium aluminate - $60,000 yr (25,000 gal/yr) Sodium hypochlorite - $4,200 yr (2,700 gal/yr) Citric acid - $18,000 yr (2,000 gal/yr) Budgeting $1.8M/10 yrs for membrane replacement 4

5 Bottom Line $1.23 / 1,000 gal for O&M $1.42 / 1,000 gal for O&M + CR $3.80 / 1,000 gal for O&M + CR + bond construction Meeting all permit limits! Is it worth it?... Crockery Township Clean Water Plant 5

6 Crockery Township Clean Water Plant Background Start-up was January 1, 2006 Membranes installed for 75,000 GPD (2 500B cassettes w/ 8 modules per cassette) (32 module equivalent) Average flow of 12,000 GPD (16% of design) Permit Limits (mo. average) 0.5 mg/l NH3 4 mg/l CBOD 20 mg/l TSS 0.15 mg/l Phosphorus 200 cts fecal Coliform Crockery Township Clean Water Plant Operations Phosphorus removal with alum Aluminum AL:P 3.5:1 (5:1) MLSS 8,000-12,000 mg/l Flux rate y 10 gf 2 d (designed 10 gf 2 d) Maintenance cleaning as needed (alternating hypochlorite and citric acid) Recovery cleaning once yearly (hypochlorite and citric acid) Good membrane performance with some losses in permeability 6

7 Crockery Township Clean Water Plant Operational Solutions Batch discharges Reduced electrical usage (42% reduction) Fewer labs (75% reduction) Labor is reduced (50% less) Long SRT to promote endogenous bio activity Reduced sludge production (yield = ) Aeration blower timers On/off air cycles eliminated foaming issues Recover alkalinity (10% reduction of NaOH) Reduced electrical usage (27% reduction) Crockery Township Clean Water Plant Operational Costs Electric - $13,100 yr (276 KWH/day) Aluminum Sulfate - $1,100 yr (997 gallons) Sodium hypochlorite & Citric acid - $150 yr Sodium hydroxide - $1,100 yr (191 gallons) Budgeting $100K/10 yrs for membrane replacement 7

8 Crockery Township Clean Water Plant Bottom Line $22.21 / 1,000 gal for O&M $24.77 / 1,000 gal for O&M + CR Meeting permit limits! (had some difficulties meeting phosphorus limit consistently) Is it worth it?... Traverse City Regional Wastewater Treatment Plant 8

9 Traverse City Regional Wastewater Treatment Plant Background Retrofit start-up was July 2004 Membranes installed for 8.5 MGD ( C cassettes w/ 32 modules per cassette) Average flow of 4.3 MGD (51% of design) Community based effluent limits 1 mg/l NH3 4 mg/l BOD 4 mg/l TSS 0.5 mg/l Phosphorus Traverse City Regional Wastewater Treatment Plant Operations Biological phosphorus removal Ferric chloride MLSS <10,000 mg/l (14 day SRT) Flux rate ave 9.2 gf 2 d (9.7 gf 2 d design) Maintenance cleaning weekly (alternating hypochlorite and citric acid) Recovery cleaning once yearly (hypochlorite and citric acid) Membrane performance is same as new 9

10 Traverse City Regional Wastewater Treatment Plant Operational Solutions Reduced electrical costs by ⅓ 10/30 air scour Vacuum pump run time reduction RAS pump timer Isolated causes and solutions to biological membrane fouling Found solutions to prevent foaming Traverse City Regional Wastewater Treatment Plant Operational Costs Electric - $ 0.22 / 1,000 gal Ferric chloride - 55,000 gal/yr of 40% Sodium hypochlorite & Citric acid - $23,200 yr 10

11 Traverse City Regional Wastewater Treatment Plant Bottom Line $1.34 / 1,000 gal for O&M Meeting community effluent limits! Is it worth it?... Is membrane treatment worth it? Larry Campbell, Superintendent, PARCC Side CWP Yes, the performance and effluent quality is worth it if the permit requirements demand this level of treatment. Operators also are enthusiastically behind the use of membranes. 11

12 Is membrane treatment worth it? Joe Hebert, Chief Operator, Crockery CWP Yes, the effluent quality is excellent and I like the operations, but the costs may not work well for small treatment plants without having the economy of scale. Is membrane treatment worth it? Scott Blair, Superintendent, TC Regional WWTP Yes, for us and our community, meeting high effluent quality standards was very important. Plus, we were severely limited on space for expansion, so there were few better options facing us when we upgraded the plant. 12

13 Joe Hebert, Chief Operator Crockery Township Clean Water Plant Ottawa County Road Commission, Department of Public Utilities Office: Cell: