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HomeMy WebLinkAbout05292012 City Council Work Session Notes - Water Facility Plan WORK SESSION NOTES ON Loodi Poi n7 WaSie. wa-kr foci 11 -4A p Purpose: 1 ( VW ‘Pikri Q red (bi SI1( Present: Ki Yin" 11)11k, / Council Member Present: 'ajAi K, of, •••ofa, ati ArMigrjari (2--Ail ' t ' - • O.' LC Called by: ,OU/4 G( Time 5 .,a6 40,--r) Date 5/c9-14,10/0., Lartil 01101/11/fliAic pfti Itt/A ired tt& Ptet vui u v , 110 U \PeYVVII prI)C,CC e 144U priA ga- OCf&rpawiLit Pintlects --flkhort p let n • .2_0 Pk( CA/\ 1-kl4C100-44 4 1 City of Seward Lowell Point Wastewater Facility Plan - Fact Sheet - Purpose Producing a wastewater facility plan is one of the requirements of the Alaska Department of Environmental Conservation(DEC)in permit AK0021890 issued to the City of Seward on June 24, 2011. A facility plan looks at existing conditions, identifies deficiencies,projects future needs, and identifies priorities for capital improvements. The City of Seward has chosen a 10-year planning horizon. Background Seward wastewater is treated at the Lowell Point Wastewater Treatment Facility, almost 2 miles south of the Alaska SeaLife Center(see Figure 1). This 6.5 acre aerated lagoon was originally constructed in 1980,has a volume of 30 million gallons, a depth of 22.5 feet, and a typical daily flow of 500,000 gallons (0.5 mgd). Because of a failure of its liner, the lagoon had a major renovation in 1993 when it was drained, sludge removed, liner replaced, and dividing wall,new air piping, and diffusers installed. Performance With very few exceptions,the lagoon has operated satisfactorily without major maintenance. And until the summers of 2010 and 2011,the very few violations of permit requirements could usually be attributed to a malfunction of a minor piece of equipment or an inadvertent operator oversight. However, in July and August 2010, effluent Biochemical Oxygen Demand(BOD), a measure of the organic strength of wastewater,slightly exceeded the permitted monthly average of 45 mg/L (parts per million). It again exceeded this limit during July-September 2011 and in August fecal coliforms (FC), an indicator of bacteriological contamination, also exceeded the permitted limit. In some cases these exceedances may have been related to sampling anomalies, or the fact that only two samples are usually collected each month,but more of them likely are from substantially increased and sustained organic loading from transient summer populations. For both summers effluent quality improved dramatically soon after Labor Day. Further information on plant performance and its capacity is in Appendix E of the Wastewater Facilities Operation &Maintenance Plan, December 7, 2011. Deficiencies Issues for improvement we have previously identified and discussed with City staff include: 1. Sludge needs to be removed. 2. The electronic temperature monitor should be calibrated to a laboratory-grade thermometer. 3. Operators should take Dissolved Oxygen(DO)readings in Cell 1. 4. pH should be cross-checked•occasionally with the SGS lab on duplicate samples. 5. Addition of remote monitoring will assist operators and improve reliability and security. 6. The City should purchase a spare air blower. 7. Operators should make minor site repairs identified in our Wastewater System Evaluation report. 8. The Control Building needs regular housekeeping attention and clean-up. 9. Laboratory records and DMRs need to be reviewed carefully before submittal to DEC. Wasteloads The plant's typical winter load is 600 to 800 pounds of BOD per day, about what is expected from a community the size of Seward with a resident population of 2,700. This loading is still considerably less Michael L.Foster&Associates SEWD-SEWD-015-0001 Lowell Point Wastewater Facility Plan May 23,2012 Fact Sheet Page 1 than the winter design capacity of 1,20Q pounds. However, during summer months the lagoon has typically seen daily loads of 1,600 to 2,100 pounds, and even higher. Occasional high wasteloads can be easily handled by the plant,because detention time in the lagoon at normal flow is up to 60 days, but sustained high organic loading has an observable effect. The summer design capacity is estimated to be 2,000 pounds, which has been exceeded during the last two summers. Wasteloads are typically a function of population,unless a community has substantial contributions from industrial or commercial dischargers. Nearly all of Seward's wastewater is domestic sewage(for example, from toilets,showers,and sinks). And although Seward's resident population has been fairly stable(it actually decreased by 4.8 percent from 2000 to 2010 according to the U.S. Census),transient populations from tourist,recreational and seasonal visitors increased during this same time. These populations have an effect on wastewater facilities. Economic conditions will impact travel,and although these are difficult to predict,we believe it is reasonable to assume current wasteloads will continue to be discharged during the next decade. They might even increase, particularly if gas prices drop and national and global economies improve. We believe it is prudent to plan for sustained summer loading of 2,400 pounds of BOD per day. To meet permit requirements consistently under these conditions, improvements are necessary. We rank the following treatment improvement options in order of increasing cost. Their benefits, risks, and costs are summarized in Table 1. Treatment Options 1. Manage wasteloads. One low cost approach is to reduce summer discharges of high strength wastes. This may mean banning septage discharge from customers outside the City limits. Any septage from pumping inside the City limits,if it occurs,should be restricted to September through April. Pumping from portable toilets should be strictly controlled. These wasteloads should be identified and any odor-masking chemicals must be biodegradable and pre-approved for discharge. Otherwise,biocides discharged in large quantities could hurt operation of the lagoon. The City should also get a handle on loads generated and discharged by local cruise operators ("daytrippers")and discourage the use of garbage grinders. It should also change how SGS Laboratory runs the.BOD test. We recommend that SGS run a side-by-side test during the summer months with nitrification inhibition in half of the effluent samples. 2. Remove sludge. This has not been done for more than 18 years—and typically an aerated lagoon would be cleaned at least every five years. Accumulated sludge has an impact on the effective volume of the lagoon, efficiency of its aerators, mixing, and storage or organics during the winter and their release during spring warming. The City has loan funds to remove sludge, and is planning on this project after Labor Day. 3. Install baffles.This is a reasonably low cost method to improve BOD removal,perhaps by as much as 20 percent, or more. One or two baffles constructed of polyethylene ribbons(trade name Bioreef)would be installed in the first lagoon cell,subdividing it into two or three"subcells." These would serve several purposes: First,they would reduce short-circuiting of the wastewater as it moves through the treatment process. Multiple cells typically produce a better quality effluent. Second,they provide a fixed substrate on which additional microorganisms can grow and further degrade the organic content of the wastewater as it passes through it. And third,they would enable separation of the lagoon contents so sludge can be recycled from the second and third subcells back to the first cell,perhaps with with floating clarifiers, increasing the concentration of microorganisms in contact with influent wastewater, and enhancing treatment. Michael L.Foster&Associates SEWD-SEWD-015-0001 Lowell Point Wastewater Facility Plan May 23,2012 Fact Sheet Page 2 4. Biological pre-treatment. This could reduce summer influent wasteloads by half,bringing lagoon loading well within its design capacity. We have assumed modifications will include a rotating screen,activated sludge aeration basin(75 feet long by 20 feet wide)and a 40-feet diameter clarifier,with recycle pumps and controls. Other combinations of biological unit processes are possible and should be considered if this option is pursued. Space is limited at the current plant site, so land may need to be purchased. 5. Expand the lagoon. Land would need to be purchased east of the existing lagoons to provide room. We have assumed this option will require a doubling of the current lagoon capacity. Disinfection Currently the City does not disinfect effluent from the treatment plant,yet with few exceptions it has been able to meet its permit requirement for FC consistently. The new permit issued in 2011 reduced the allowable FC concentration, creating more of a challenge during summer months. However, field testing so far in Resurrection Bay confirms outfall dispersion modeling that Seward is still able to meet Alaska Water Quality Standards for FC at the edge of the mixing zone. We believe the observed permit excursions last summer will be improved sufficiently by other operational changes so Seward will not need to provide effluent disinfection. However, if it is added, we suggest onsite generation of sodium hypochlorite from saltwater and electricity. In 2008 we evaluated this as an option for drinking water disinfection when and if the City decides to change out existing gas chlorination. The outfall line is 3,500 feet long and will provide one hour of chlorine contact at normal flow,perhaps eliminating the need for a separate chlorine contact chamber. Table 1 Summary of Treatment Options 9A ` a � Could reduce high strength loads with minimal cost;run extra set of effluent BOD tests with 1—Manage Wasteloads $2,000 inhibition of nitrification for three summer months(about$300). Housekeeping task that has not been done for 18 2—Remove Sludge $200,000-$300,000 years;may improve plant performance,possibly reducing summer effluent BOD considerably. Creates smaller compartments,provides fixed media substrate for microorganism growth; may 3—Install Baffles $200,000-$300,000 reduce effluent BOD by 20+%. Could adapt later with sludge recycling. Use high-rate activated sludge process during summer months to reduced.BOD loading to 4—Biological Pre-treatment $2 to$2.5 million lagoon;will require more land,operator attention,and aeration. Essentially a duplication of the existing.lagoons; 5—Expand Lagoon $4.5 to$6 million will require almost the same amount of additional land and more aeration. Will not be required if the plant can meet FC Effluent Disinfection $80,000-$100,000 limits;this will also have ongoing O&M costs. Michael L.Foster&Associates SEWD-SEWD-015-0001 Lowell Point Wastewater Facility Plan May 23,2012 Fact Sheet Page 3 Implementation These improvements will take investment by the City. We recommend the first two be part of any plan. They might enhance lagoon performance sufficiently to ensure satisfactory performance for several more years. However,the City should also consider the third option—installation of one or two"Bioreef' curtains to further enhance lagoon performance. If necessary,this could later be further modified by installing floating clarifiers in the second and third subcells to return sludge to the beginning of the treatment process, improving lagoon performance even more—and at fairly low cost. The City may be able to pay for the recommended improvements with cash from its Sewer Fund revenues,but it also wants to have capital available for other deferred maintenance. The financing cost for options 2 and 3 is equivalent to $60 to $100 per year($5 to$8 per month)for each residential customer. Although the fourth and fifth options will provide capacity and security substantially beyond the first three options,we do not believe they will be necessary during the 10-year planning period. In addition to their substantial capital investment,they also will require more power for aeration and pumping—and additional operator attention. A decision on additional investment in the treatment facilities can be made after observing over the next several summers performance changes from the recommended changes. Public Input The City Council will not be making final decisions or commitments at its May 29 work session; however, we welcome its input as part of planning for the future,especially for the critical summer periods when Seward's transient population increases dramatically. Other public input at the meeting is also welcome. Written testimony will also be accepted as we further develop the wastewater facilities plan,which is due to be submitted to DEC by August 1. To submit written testimony or get more information, contact W.C. Casey,Public Works Director,at 224- 4005 and wcasey@cityofseward.net; or Loren Leman,P.E. at 696-6209 and Idl@mlfaalaska.com. Michael L.Foster&Associates SEWD-SEWD-015-0001 Lowell Point Wastewater Facility Plan May 23,2012 Fact Sheet Page 4 Figure 1 Lowell Point Sewerage Facilities ` �` {fitt 1 1 pyyy� 149" —1 ga�J -I �' t t44 2S i6 Id 5-1 (� I E - gc1----_,- , -5r: - . ' ' ' '.- ', ,,,',, ,,144r5 L I'g:, , ...--,,' I L ~I ,- PUMP S IA]ION:1t3 L/ —G9'a5'42 RESURRECTION BAY _ _ __Bo.OF oe �t OWCL6 POINT ROAD OUTFALL. r .. o• Bao: 1200 7400 .. ' —5 i'o4'30' i / O&M Plan \ - \ Seward,Alaska �U�4O GOO LOWELL POINT 4, �Qe (L li �owcta' o SEWERAGE FACILITIES 1 ''\ << � _ aun nu suwmsuwaou.uoo2 cvuwv' Figure 3 -_.,-7— •% �"' �{ Novemberi5,2�1t f>iG iG:�f.1N:HAr:C_v� Michael L.Foster&Associates SEWD-SEWD-015-0001 ' °•Sheet Point Wastewater Facility Plan May 23,2012 Page 5 •