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

final clarifiers that follow RBCs range between 400 and 600 gpd/sf. lit III The sludge wasted from the final clarifiers is pumped by the sludge pumps to the removal of gravity thickener or to the first- stage anaerobic digestion basin. The in sludge, or waste sludge, from the system is necessary to keep the amount of sludge the system from increasing to an unacceptable level, due to the continued growth of III microorganisms in the system. Scum is removed at the clarifiers and the secondary sludge is pumped to the gravity thickener using three ( 3) non- clog centrifugal pumps. The drives have recently been replaced and the concrete and pumps at the final till clarifiers appear in good operating condition. WWTP staff noted that very little wasted sludge is removed from the two ( 2) final clarifiers. The low volume of sludge from the final clarifiers is primarily due to the low organic loading to these units. III III As with the primary clarifiers, each unit of the final clarifiers can route the flow to the other clarifier during times of required maintenance. Figure 2- 14 shows photographs of the City' s two ( 2) final clarifiers. lilt F:\2001\ 01.0387. 000\Report\ R-4\041403 FINAL\ SEC 2. doc HAI#01.0387.000 2- 24 04/ 14/ 03  Figure 2- 14 City of Fort Walton Beach Wastewater Treatment Plant Facilities Plan Final Clarifiers Photos South Final Clarifier North Final Clarifier F:\200 1 \ 01. 0387 . 000\Report\ R-4\ 041403 FINAL\ SEC 2. doc HAI#01.0387. 000 2- 25 04/ 14/ 03 tII lId iii 2. 3.2. 5 Disinfection I From the secondary clarifiers, the effluent flows by gravity to the chlorine contact chamber. The chlorine contact chamber provides a zone for the selective destruction of disease- causing such bacteria, viruses and anaerobic cysts I organisms, as contacting the clarified effluent with a chlorine solution for a designated period of by time. I The chlorine contact chamber at the City's WWTP consists of a single baffled I chlorine contact basin. The basin is a cast- in-place basin with baffles constructed of concrete filled Concrete Masonry Units ( CMUs). The chlorine contact chamber basin I is 39.5- feet long by 40.3- feet wide with a maximum operating sidewater depth of 9. 17- feet and baffled to a length to width ratio of 85. The basin has a working volume of approximately 15, 667 gallons. The contact time in the chlorine contact I chamber is 37. 5 minutes at the pennitted flow capacity of 4.50 MGD, which is more than double the pennit required time of 15 minutes. The chlorine residual sampling I for R001, the onsite sprayfield, is taken at the chlorine contact chamber. The chlorine residual sample location for R002, the sprayfield at the golf course, is 100 feet north E prior to the golf course' s above ground storage tank and after the Chlorine Injector Box in the effluent discharge pipe. t The chlorination facilities at the City's WWTP consist of two ( 2) 500 pounds per day lbs./ day) gas chlorinators. During nonnal operation there are two ( 2) cylinders on- I line tied to a single 500 day chlorinator and an automatic switchover at the each lbs./ tank is activated when operating pressure reaches a minimum value. Feed water for the chlorine solution is provided at the facility by drawing off the effluent supply. In addition, the chlorine storage building is equipped with a chlorine leak detector. The II Ii chlorination unit is equipped with a remote injector that is located immediately downstream of the Parshall flume. The chlorine feed rate is automatically controlled E by a 4- 20 ma signal from the flowmeter transmitter located at the Parshall flume. The chlorine is piped to the via tee fitting to downstream of the Parshell flume and the head of in plant water line. II Based on the facilities installed, the existing disinfection facilities are adequate to I meet the City' s wastewater treatment requirements during nonnal operation. However, the structure of the chlorine contact basin is deteriorating and the interior I F:\2001\ 01.0387. 000\Report\ R-4\041403 FINAL\ SEC 2. doc HAI#01.0387. 000 2- 26 04/ 14/ 03 I l1li Ii II baffle walls are in need of rehabilitation, and presently, the configuration of the chorine contact chamber does not allow for a by-pass of the influent for maintenance for disinfection. Also, purposes and still maintain the contact time requirements provisionsto isolate portions or take down the chlorine contact basin for maintenance pi is not possible. II Figure 2- 15 provides photographs of the chlorine contact chamber. I I I I I: 1M t pt' fill' I P- i. I I F:\2001\ 01.0387. 000\Report\ R-4\ 041403 FINAL\ SEC 2. doc HAI#01.0387. 000 2- 27 04/ 14/ 03 I  Figure 2- 15 City of Fort Walton Beach Wastewater Treatment Plant Facilities Plan Chlorine Contact Chamber Chlorine Contact Chamber Facing Northeast Chlorine Contact Chamber Baffle Walls F:\200 1 \ 0 1.0387 . 000\Report\ R-4\ 041403 FINAL\ SEC 2. doc 2- 28 04/14/ 03 HAI#01.0387. 000 fill w 2. 3.2. 6 Effluent Filters Effluent from the City' s WWTP used at the City public golf course is passed through ill a denitrification filter prior to transmission to the golf course. The filter consists of four ( 4) trains with three ( 3) units of approximately 150 square feet. The filters are I Parkson Dynasand units and were constructed in 1992. Originally, the system was designed to utilize methanol for denitrification, but this practice was never used. I Polyaluminate chlorate is currently added prior to the filters as a coagulant to aid in additional solids removal. Effluent from the filters is chlorinated and then flows by I gravity to the golf course storage tank. The filters appear to be in good working condition. I 2. 3. 2. 7 Residuals Management Facilities I Removing solids from the liquid, thickening, stabilizing, dewatering, and using or disposing of biosolids is often a more difficult challenge, both technically and I operationally. Further, the improper management of biosolids has the potential to create damage to the environment sometimes in a greater magnitude than wastewater effluents. The residuals management facilities at the City's WWTP consist of a conventional gravity thickener and a two- stage anaerobic digestion system to stabilize i. the sludge generated in the treatment process and vacuum coil filters to dewater the iii sludge prior to disposal. Sludges are stabilized to reduce the pathogens, eliminate offensive odors and reduce or inhibit the potential for putrification of the bio- solids ill produced during the treatment process. During the process of digestion, microorganisms are permitted to grow without the addition of more food. This causes the microorganisms to enter an " endogenous respiration" mode, wherein the This process results in organisms metabolize their own cellular material. more volatile material being metabolized and reduces the total mass of solids. I The sludge from the primary and secondary clarifiers is pumped to the 30- feet diameter, concrete gravity thickener. The thickener and pumps appear to be in good operating condition. From the gravity thickener, the thickened sludge is pumped to the primary or first II stage anaerobic digester. The facility' s anaerobic digesters are two ( 2) circular concrete tanks, 60- feet in diameter with a side water depth of 22- feet. The total II' i F:\2001\ 01.0387. 000\Report\ R-4\041403 FINAL\SEC 2. doc III 04/ 14/ 03 HAI#01. 0387. 000