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

2- 29 iii I volume of both anaerobic digesters combined is approximately 124,407 cubic feet. Additionally, the anaerobic digester is equipped with a device to pennit decanting of the supernatant in the digester. The supernatant is recovered and sent to the Ii headworks of the WWTP for re- treatment. The digesters currently provide a solids retention time ( SRT) of approximately 120 days. I The digesters were cleaned in 1999 and according to WWTP staff, the condition of I walls appeared in good condition. The covers to the digesters have been recently repaired and the existing mixing equipment is in poor condition. Figures 2- 16 and 2- I 17 show photographs of the anaerobic digesters at the site. I Sludge from the digesters is sent to a mixing tank prior to the dewatering drums. Ferric sulfate is added to the sludge prior to the mixing tank for the coagulation of the residuals. After the mixing tank and prior to the dewatering drums, lime is added to I the sludge for stabilization. Lime treatment controls conditions in biosolids that may support the growth of pathogens and increases pH. In addition, it converts wastewater II sludge into a more usable product for agricultural use plan disposal, and reduces metals leachability. Lime treatment also improves biosolids density and physical f!! Ii handling characteristics. No polymer is currently added to the sludge. There are two ( 2) Komiline Sanderson vacuum dewatering drums that are each 8- feet long by 5- feet wide. Water drained from the sludge is collected and pumped using filtrate pumps to the head works of the facility. The sludge that is applied to the vacuum filters will nonnally dewater to approximately 50 to 75- percent solids. The dewatered sludge is then removed from the vacuum filters and hauled by City Ii personnel and using City equipment to a pennitted Agricultural Use Site, Earl King Fanus, near Freeport, consisting of268 acres. The evaluation of the residuals management facilities, historical data, and the operation of the facilities indicate the system is adequate for the present design condition of 4.50 MOD. Figure 2- 18 provides photographs of the City' s dewatering operations. 1. However, it should be noted that the State of Florida is presently evaluating the t1i i treatment and disposal of Class B sludges, which includes the type of sludge that is treated and ultimately disposed by the City. Based on recent workshop meetings, it II F:\2001\ 01.0387. 000\Report\ R-4\041403 FINAL\SEC 2. doc HAI#01. 0387. 000 2- 30 04/ 14/ 03 M  appears that the State is leaning toward either banning the land application of Class B sludges or significantly restricting their uses by increased set- backs, increased monitoring, site specific pennits and/ or liability issues regarding the ultimate use being switched to the land owners. If Class B residuals are banned in the State of Florida, the City can either convert their treatment system to a Class A system or I dispose of their sludges in a landfill, similar to the disposal of grit and screenings. Assuming that Class B residuals will be banned, the options to meet Class A I treatment requirements includes compo sting, chemical pasteurization, autothennal aerobic digestion ( ATAD), heat treatment and/ or advanced alkaline stabilization. At I the present time, these Class A options were not investigated further for the following reasons: I The disposal of Class B residuals is still currently an acceptable option available to the City. I The conversion to a Class A treatment process, may impact the land fill application practices presently used at the Earl King land application L sites based on the type of process used, and the agronomic requirements of the site. The final rule modifications will most likely not become effective within the next 5- years, due to potential legal actions. It is unknown at this juncture in the workshop discussions what the increased monitoring and setback requirements, as well as what other restrictions will be imposed for the treatment and disposal of Class B III residuals. II II! Ii. fill II I I I F:\2001\ 01.0387. 000\Report\ R-4\041403 FINAL\ SEC 2. doc HAI#01.0387.000 2- 31 04/ 14/ 03 I  Figure 2- 16 City of FortWa.1ton Beach Wastewater Treatment Plant Facilities Plan Anaerobic Digesters Photos Anaerobic Digesters facing West North Anaerobic Digester F:\2001\ Ol. 0387. 000\Report\ R-4\ 041403 FINAL\SEC 2. doc HAI#01.0387.000 2- 32 04/ 14/ 03  Figure 2- 17 City of Fort Walton Beach Wastewater Treatment Plant Facilities Plan Anaerobic Digester Photo Top of Anaerobic Digester F:\2001\ Ol.0387. 000\Report\ R-4\ 041403 FINAL\SEC 2. doc HAI#01.0387. 000 2- 33 04/ 14/ 03  Figure 2~18 City of Fort Walton Beach Wastewater Treatment Plant Facilities Plan Residuals Dewatering Operations Photos Dewatered Sludge Leaving Vacuum Drums Sludge Loading for Hauling to Agricultural Use Site F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\SEC 2. doc HAI#01.0387. 000 2- 34 04/ 14/ 03 I 2.3.2. 8 Plant Recycle Pump Station I The City' s WWTP has a pump station adjacent to the grit cyclone and classifier that receives all plant flows from the vacuum coil drums filtrate, anaerobic digesters, gravity thickener supernatant and miscellaneous plant drains. The discharge from this I pump station is pumped to the headworks of the plant for treatment. The station consists of a cast- in-place concrete wetwell with three ( 3) submersible pumps. This I pump station is severely corroded, specifically at the air/wastewater interface and freespace above the wastewater level in the wetwell. Moreover, the aboveground I piping network at the pump station exhibits severe corrosion. City staff have reported pump failures and subsequent repairs due to aggregate and debris from the I deteriorating concrete walls entering the pumps. The City has initiated repairs of the pump station and renovation is expected to be I complete in May 2003. 1.'....\. II Figure 2- 18 shows photographs of the City' s plant recycle pump station. III! fill III! II III it. I F:\2001\ Ol.0387. 000\Report\ R-4\041403 FINAL\SEC 2. doc HAI#01. 0387. 000 2- 35 04/ 14/ 03 I  Figure .2- 19 City of Fort Walton Beach Wastewater Treatrnent Plant Facilities Plan Plant Recycle Pump Station Photos Plant Recycle Pump Station Facing Southwest Plant Recycle Pump Station Wetwell F:\ 200 1 \ 0 1.0387 . 000\Report\ R-4\ 041403 FINAL\ SEC 2. doc HAI#01.0387. 000 2- 36 04/14/ 03 II LJ 2. 3.3 Effluent Disposal The City's WWTP is currently permitted to discharge 4. 50 MGD of treated wastewater. The Ii effluent from this facility is disposed of by reuse land application to the restricted access sprayfield and public access golf course. The existing permit conditions are as follows: I 3. 1 MGD maximum monthly average daily flow to restricted access land application slow- I rate sprayfield irrigation system ( ROOl). Discharge is to a 400- acre sprayfield site adjacent to the WWTP. I 1. 55 MGD maximum monthly average daily flow to public access land application slow- rate sprayfield irrigation system ( R002). Discharge is to a 2. 0 million gallon holding tank at the Fort Walton Beach municipal golf course with subsequent discharge to the 200- acre I expandable to 300- acres), 36- hole golf course. I The chlorine residual and fecal coliform samples of the disinfected effluent leaving the chlorine contact chamber are sampled at the following location: I ROOl - the onsite restricted access sprayfield, is taken at the discharge from the chlorine I contact chamber. R002 - the golf course, 100 feet north prior to the golf course' s above ground storage tank