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

To address the future requirements of the system, the analyzed data consisted of historical population and wastewater customer billing data provided by the City, and historical plant flow I data as reported in the FDEP DMR' s. Utilizing this data, conclusions regarding the population and wastewater flow projections were developed for this system in order to characterize future I trends within the City of Fort Walton Beach wastewater service area. I Population data is extremely useful in developing customer and/or flow projections to meet the wastewater service needs of a designated area. The current population data was obtained from D the City' s Department of Community Development Services. The population growth within the City, as reported by the 1999 to 2000 census showed a reduction in population. The population as of April 1, 2002 is 20, 239. The predicted increase by the Community Development Services is 100 to 200 people per year for the next 10 years. At 200 people per year, this is less than a 1- in developing the population percent increase per year. Therefore, the I- percent value was used I. projections for the City. I. The wastewater flow projections were based on the evaluation of several historical databases and the analysis the population projection that were previously described. The flow projections facilities in developed for this Facility Plan were used to determine the adequacy of the existing treating future flow projected, and any required changes to the existing plant capacity. I.:: Additionally, these wastewater flows will serve as the basis for the City' s future wastewater I capital improvements program and establishment of timelines to accomplish any improvements in order to meet the customers' needs and maintain the required level of service. I I F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\ SEC 3. doc HAI#01.0387. 000 3- 10 04/ 14/ 03 I ill I The first wastewater flow projection method evaluated was based on a linear regression of the historical flows from January 1999 to June 2002 of the City' s WWTP. Data from the 1998 was I not included in the regression analysis due to the III flow spikes. The best- fit line of the historical data was then extrapolated linearly to project influent monthly average wastewater I flows throughout the 10- year planing period. Based on this method the monthly average daily wastewater flows for the City' s WWTP were estimated to range from an actual 2.434 MGD in June 2002 to 1.993 MGD in June 2012. This is a 1.93- percent decrease in monthly average flow I each year. While this method provided an estimate of wastewater flows, it also included the III contribution to the system, and basically appeared to have no relation to the growth of the system I due to new customers and recent trends in development. Moreover, this method also assumed that the III would continue to decrease at the same rate as it has during the past, and did not I illustrate the impacts of the City' s annual III rehabilitation program. In addition as noted above, this method appeared to not accurately illustrate the future growth in the area, particularly the I approximate I- percent per year. Considering the land use analysis showed undeveloped land represents only approximately 8- I percent of the total use, the anticipated future growth in the City' s service area will be negligible, and will consist primarily of redevelopment. Based on this infonnation, the projected flow rates I were adjusted using new infonnation regarding development growth and trends within the City's wastewater service area and the on- going III reduction program. As a result, the influent I wastewater flow to the City' s WWTP is anticipated to remain generally at the present annual monthly average flow of 2.421 MGD to a maximum 5- percent increase in 10 years to 2. 542 I MGD in 2012. pili I I I I I F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\SEC 3. doc HAI#01.0387. 000 3- 11 04/14/ 03 I  SECTION 4 ALTERNATIVE SECONDARY TREATMENT UPGRADE OPTIONS 4. 1 INTRODUCTION I The construction of the City' s existing WWTP was completed in 1980 and the plant consists ofa fixed film biological facility, which utilizes rotating biological contactors ( RBCs) for wastewater I treatment. The aging RBCs have been experiencing mechanical failure over the past several years and the City is investigating treatment alternatives to replace the fixed film process with I the same type of process or a suspended growth activated sludge process. The existing RBC drive units have been experiencing failure due to the aging mechanical components and inherent I design issues with the RBC equipment. In summary, these component failures have led to catastrophic damage to the RBC supports, media, and basin structure over the years. Figure 4- 1 I illustrates the resulting damage of a failed RBC unit. A survey of all of the RBC systems in the State of Florida was conducted, a copy of the survey I and results are provided in Appendix C of this report. In summary, there are approximately 283 WWTP' s in the State with capacities greater than 1.0 MGD. Of this total only two ( 2) of these I facilities use RBC' s as their primary means of wastewater treatment, one of which is the City of Fort Walton Beach. Furthennore, it should be noted that of that total there are only five ( 5) I facilities that use the fixed film technology (trickling filter, RBC' s, etc.) and the remaining 278 facilities use the activated sludge technology as the primary means of wastewater treatment. I This section discusses alternatives that available to correct the are City' s WWTP' s RBC operational issues and improve the overall treatment capabilities of this facility, as well as I prepare the system for future upgrades. The three ( 3) primary alternatives available to the City include the following: I 1. Rehabilitating the existing RBCs and replacing damaged units. I 2. Retrofitting the RBC basins with an advanced fixed film process, such as the ThI WesTech STM-Aerotor system. Abandoning the RBC process and replacing it with a conventional suspended J 3. 11.'" growth activated sludge process, such as an oxidation ditch. I' I F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\SEC 4. DOC HAI#01.0387.000 4- 1 041403 ill ill The above three ( 3) treatment alternatives are being presented to the City and the Florida Department of Environmental Protection ( FDEP) for planning, design and construction of either a new treatment process or rehabilitated facility, which will provide reliable wastewater treatment to the customers within the City' s service area. A 10- year planning period was I selected for this evaluation. I I I I I I I t: lilt ti~ ill fill t. I F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\ SEC 4. DOC HAI#01.0387.000 4- 2 041403 t! I II! III 4.2 WASTEWATER TREATMENT PLANT UPGRADES A~ t! As noted previously, a number of alternatives were considered for upgrading the City' s WWTP, which included rehabilitating the existing RBCs, retrofitting the RBC basins with an advanced I fixed film WesTech STM- AerotorThl system, and the replacement of the RBC process with a conventional activated sludge system. Consideration was given for meeting future requirements in tenns of flow and effluent requirements, as well as several other issues, which included: I 1. Raw wastewater characteristics and flows. I 2. Effluent requirements, and future trends in regulations. 3. Sensitivity to changes in wastewater characteristics and flow, and their effect on I operations. 4. Operational requirements. I 5. Flexibility in dealing with changing State and Federal regulations regarding the treatment and disposal of wastewater and sludge. 6. Available space for upgrading and expanding the existing facilities. I 7. Reliability of process equipment. 8. Capital and operating costs. I As discussed previously, historical flows from 1998 to the present were reviewed for the City' s I WWTP. Utilizing data presented in Section 3, the projected average daily wastewater flow in 2012 is estimated to be approximately 2. 54 MGD, assuming that the on- going III rehabilitation t program continues to address the system deficiencies that contribute stonnwater inflow and Further, influent CBODs groundwater infiltration into the City' s wastewater collection system. l1li' and TSS concentrations are both expected to remain around 200 mg/I. III Based on this infonnation, the City will maintain the existing capacity of 4. 50 MGD, which will accommodate future flows beyond the planning period discussed in this report. Sizing the facilities for this influent flow should provide sufficient treatment capacity well beyond the year pi 2012, assuming a flow rate increase of 5- percent over the 1 a- year planning period. ci'" While there are a number of alternatives available to the City to upgrade and/ or replace the City' s i.., WWTP RBC process, the analysis was reduced