Fort Walton Beach Council agenda — 04-29-03 workshop agenda — reading text

@ 25% 530.000 TOTAL $ 2. 650. 000 II JIll' irI III ilia II till F:\2001 \ OI. 0387. 000\Report\ R-4\ 041403 FINAL\table 4- I. doc 4- 10 041403 HAl #01.0387.000  Aerotor"" 4.2. 2 Alternative 2 - Retrofitting the Existing RBCs with WesTech STM- I Aerotor"" Alternative 2 includes replacing the existing RBC process with the WesTech STM - sludge process with a fixed film I System. The WesTech system combines the activated technology. II The WesTech STM- Aerotor"" assembly consists of 24 cylindrical polypropylene segmented pipe media bundles surrounding a steel center shaft and galvanized steel support framework. The I center shaft consists of a steel pipe with solid steel ends of hardened stainless steel bushings. As with the RBC process, the WesTech STM- Aerotor"" unit utilizes a gear reduction drive, which is I powered by a 5 horsepower ( HP) motor. The average required operating horsepower is between 2. 8 and 4. 0 HP per drive unit, depending on treatment requirements. The assembly measures approximately 10 feet in diameter and 15 feet in length and requires a minimum wall height of I 11. 5 feet. c!i:~ As the assembly rotates, atmospheric air is carried downward into the tank, where it is continuously released as fine bubbles. The rotational speed is varied to provide appropriate I levels of dissolved oxygen to the suspended microorganisms. A paddle on the periphery of the rotating assembly produces mixing of the tank contents. The media also provides a surface area for fixed film growth. f The manufacturer states that the system is capable of simultaneous nitrification and denitrification, as well as biological phosphorous removal, which results from the fonnation of anoxic and/or anaerobic zones in the lower portion ofthe process basin. These zones seem to act as biological selectors, accomplishing sustainable nutrient removal, while simultaneously N) to below 5 t improving sludge settling characteristics. Removal of ammonia nitrogen (NH4- II mg/l and phosphorus to below 2 mg/l can be achieved in most instances. MIl The WesTech system operates with the media 75- percent to 85- percent submerged, and similar to the RBC process, the WesTech system utilizes several basins to accommodate the rotating f assemblies. The existing concrete basins have a water depth of approximately 6. 0 feet, plus 1. 0 foot of freeboard. In addition to the basin rehabilitation discussed in Alternative 1, the existing basins would require substantial modifications to increase the water depth to the required level. iii The existing basin walls would require an extension of approximately 4.5 feet to accommodate II F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\SEC 4. DOC HAI#01. 0387. 000 4- 11 041403 till l!ji ill II. the WesTech STM- AerotorTM components, which would provide 2 feet of freeboard and a I- foot clearance between the assembly and the bottom of the basin. Extending the existing walls would substantially increase the moment transferred to the tank base slabs, which would necessitate lateral support of the walls, which is difficult and expensive. Considering the cost to rehabilitate and modify the existing basin structure it is assumed that a new structure would be constructed to I accommodate the WesTech system for this alternative. A typical WesTech system configuration III is shown in Figures 4- 4 and 4- 5. iii" The conversion to this activated sludge process will also require recycle pumping from the I secondary clarifiers. This return activated sludge ( RAS) is a necessary component for this option, and will require the addition of recycle pumps, recycle wet well, yard piping, and control I equipment to direct the RAS to the process basin. As is the case for Alternative 1, the primary clarifier will remain in operation and another 70- foot diameter final clarifier will be necessary It once AADFs approach 3.50 MGD. 4. 2.2. 1 Capital Costs I The probable opinion of capital costs for Alternative 2 is summarized on Table 4- 2. iMsit These costs are based on unit prices obtained from recent bid experience as well as infonnation obtained from manufacturers of the equipment to be supplied. As indicated on this table, the total probable opinion of cost for the upgrades to the City's WWTP to incorporate the WesTech STM- AerotorTM is estimated to be approximately 2, 938, 750. It 4. 2.2. 2 Scheduling and Sequencing 1,, 1 Based on the proposed plan described above it is anticipated that the overall program if should be completed within 2 years from inception, and is the case with Alternative 1, no downtime of the facilities should be required. The design associated with this alternative should take approximately 4 to 6 months to complete, including review periods and pennitting. It is anticipated that the II bidding, review, and recommendation for award period would require 2 months to complete. Once construction is underway, the time to reach substantial completion is Ii I F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\SEC 4. DOC HAI#01.0387. 000 4- 12 041403 I ill 11M estimated to be approximately 16- months. During the last 2- months start- up and operational modifications to bring the system on line would take place. II it t, III itf;'{ till lit III! L;.. i.. ill ill III I..;:ex F:\200 1 \ 0 1. 0387. 000\ \ - 4\ 041403 FINAL\ SEC 4. DOC ReportR HAI#01.0387. 000 4- 13 041403 I  I: o i S.l: ... cnu'" md amz JI: ll) 0.:: 0........ Il: a:I a:la: 3: ... t:~ 00( il.l.. a.. ol- I: 3: :>. u:C: 3: J t=!( I) 3: II t): ~ o 213 NO M~ 16 0' v I J H8 ~ E " t): I o o' o 11\ 1ft J)! c i a d o M g ljj 0 21 ~ I~ m 21 ~, Z 5I Ii P I- il It 2 IUlIII FIGURE 4. 5 Q1038lJJOO _) LO,. 4, 5. CDft iIIII ill TABLE4-~ CITY OF FORT WALTON BEACH i WASTEWATER TREATMENT PLANT PROBABLE OPINION OF CAPITAL COSTS WESTECH STM AEROTORTM SYSTEM Description of Work Cost WesTech STM- Aerotor System ( 20 units) 875, 000 Drive Unit Chain ( 20 units) 40, 000 11, 000 ill Bushings ( 20 units) Motors, Controls ( 20 units) 25, 000 New Concrete Basin to Accept STM- Aerotor System 400, 000 r- 110, 000 i. Recycle Wetwell 115, 000 Recycle Pumps, Controls, Rails Yard Piping Modifications 350, 000 Electrical Modifications