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

made pursuant to the results or outcome t:' proj ected herein. 4. 5 RECOMMENDED SECONDARY TREATMENT UPGRADES III F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\SEC 4. DOC HAI#01.0387. 000 4- 25 041403 i..  This section summarizes the recommended capital improvements to the City' s WWTP that are associated with only the secondary treatment portion of the facilities to meet the future 11 Ii wastewater flow projected and effluent requirements. I Summarized herein is an economIC and subjective analysis of the alternatives recommended improvements with regard to upgrading the City's WWTP to improve the overall and the efficiency and performance of the facility. i I I I III I t I F:\2001\ Ol. 0387. 000\Report\ R-4\ 041403 FINAL\ SEC 4.DOC HAI#01.0387. 000 4- 26 041403 ill  TABLE 4- 4 Ii CITY OF FORT WALTON BEACH WASTEWATER TREATMENT PLANT I PRESENT VALUE ANALYSIS SUMMARY w Total Present Process Present Value Residual Value Value I Rotating Biological Contactor $ 5, 887, 585 ($ 950, 000) $ 4, 937, 585 WesTech STM- AerotorTM $ 5, 298, 999 ($ 656,250) $ 4, 642, 749 I MLE Process ( Oxidation Ditch) $ 6, 715, 312 ($ 925, 000) $ 5, 790, 312 i I I I I I II fc Iii k III F:\2001 \ 0 1.0387. 000\Report\ R-4\ 041403 FlNAL\table 4-4. doc HAI#01- 387. 00 4- 27 041403  4. 6 WEIGHTED ALTERNATIVE ANALYSIS To detennine the most appropriate alternative, each process alternative was scored and ranked based on criteria in relation to its relevance to the project. Each of the alternatives were scored I and ranked based on the following considerations: 1. Ability to meet future requirements. I 2. Lifecyc1e cost. 3. Ease of expansion. I 4. Process reliability and stability. 5. Mechanical reliability and stability. I 6. Future resources to maintain process. 7. Ease of maintenance. I 8. 9. Site requirements. Staffing requirements. 10. Capital Costs. I The above considerations numbered one (1) to nine ( 9) were weighed on a scale of one (1) to I three ( 3) with a score of one (1) being least important and a score of three ( 3) most important for project consideration. However, item number 10, " Capital Costs", was weighed on a scale of I one ( 1) to eight ( 8). I The weighted scores were totaled for each alternative and process selection was based on the scores shown in Table 4- 5. The resulting scores from the subjective analysis were as follows: Process Weighted Score Alternative 1 - RBC 61 II Alternative 2 - WesTech STM- AerotorThf 50 Alternative 3 - MLE Process 71 Ii Based on the results of the subjective analysis of the three ( 3) alternatives, the MLE process was II, the most favorable alternative option. II r l1li F:\2001\ 01.0387. 000\ \ - 4\ 041403 FINAL\ SEC 4. DOC ReportR HAI#01.0387. 000 4- 28 041403 l1li iii 4.7 RECOMMENDED ALTERNATIVE i Based on the findings discussed in this section, it is recommended that an oxidation ditch MLE system be constructed to replace the RBC system. While this option is the highest in terms of I capital outlay, it provides the City with numerous advantages over the other three ( 3) alternatives considered. As noted previously, there are approximately 283 WWTPs in the State of Florida with permitted capacities from 1.0 MGD and greater. Ofthese WWTPs, 101 of these facilities or I approximately 35. 7- percent are oxidation ditch facilities. Moreover, recent trends have been to replace fixed film treatment processes, similar to the City' s with activated sludge systems similar I to the one recommended for the City. The MLE systems are predominantly aerobic processes that achieve relatively high microorganism concentrations through the recycle of biological I solids. In addition, an added advantage of this type of system is this process can be modified to achieve a higher degree of treatment, such as for nutrient removal, should the need arise. I Based on the anticipated hydraulic and organic loading rates, and the potential for future more stringent regulatory requirements, it was determined that an oxidation ditch system best fit the I needs of the City. Furthermore, since these improvements will consist of new structures and yard piping on- site, provisions will be incorporated into the design to accommodate the I anticipated ranges in both hydraulic and organic loadings that the aeration basin and secondary clarifiers will experience, as well as provisions for higher degrees of nutrient removal should the I" need arise. Moreover, since this system will be designed with relatively high HDTs, and SRTs ranging from 20 to 30- days, it should provide some buffer to provide adequate treatment during lilt Ii periods of wide swings in both hydraulic and organic loadings. I! IIII Based on the projected wastewater flows that may be experienced at the City' s WWTP, it was iW concluded that the oxidation ditch system should be sized to treat an average daily flow of 4. 5 III MGD. This capacity would provide the City with sufficient capacity through the planning period Ii of year 2012, based on the projected demands and information provided from the City. fill' i. pi 1 l1li F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\SEC 4. DOC HAI#01. 0387. 000 4- 29 041403 pi lit lit cI f') ill o I 1' Q 0" I(" I 0" 0" f')(" f') 1 O"IO" I(" Ooo f')\ r-- 1' I o Q CI I o I II f')(" f')(" f')-(" f') f') (" f')- f')(" f')(" (" I Q Q o(" O("f')-\ O~ f')(" f')(" f')\ f')(" In Q 00 I E-< 00 u I) 8' I E M I II N-- N---(" N f')(" f') c.. o E-<~ 1::: o c.. I u~~ E-< S I E-<~ u O"I-\ f') o(" f')(" f')(" O~