The city of Palm Coast, FL, WWTP is rated for 6.8 MGD, and over the years has grown to where it now receives an inflow of 6.3 MGD. Faced with aging equipment and minimal excess capacity, the plant has little flexibility when handling upset conditions. Unfortunately, the plant has been struggling with their aging centrifuge for some time. Since they only have one centrifuge with no redundant units installed, when the unit goes down it seriously affects the ability of the plant to maintain the removal of solids out of the plant. Within the last year, the centrifuge needed servicing and was sent out for a rebuild that took almost six months to complete.
Not long after resuming normal operations, additional problems with its motor resulted in the centrifuge currently being out of service for another three months or longer. When the centrifuge is running it is able to process between 80-120 gpm, which barely keeps up with the plants current normal wasting schedule volume. The result of this dewatering downtime was that the MLSS concentration has doubled in the plant. To continue to meet effluent limits, the utility was forced to add polymers into their process to flocculate and settle solids within the plant. The utility began to seek options for rental equipment in the market that could not only remove solids from the plant but also be large enough equipment to help them “catch-up” with solids removal while the centrifuge is being fixed.
The solution has been the rental of a Schwing Bioset, Inc. (SBI) trailer mounted model FSP1103 screw press through the rental and operations company SBI Rents. The large unit from SBI Rents is able to process in excess of 300 gpm of incoming feed, which allows the filling of a 25-ton trailer in a 5-hour period. Currently dewatering to 10-hr each day and filling two trailers per day, at this rate, the goal of the plant is to get the MLSS back into their normal range and be caught up within a 6-8 week period. Assuming the centrifuge has been repaired again and can resume normal operations, plant operations will be back to normal.
There are few screw press manufacturers that make large throughput machines, and fewer yet that have appreciable experience. However, SBI has a lineup of over 17 machine sizes and has a great deal of experience manufacturing large screw presses and, in particular, mobile units. In addition to fixed machinery that is installed within a plant, SBI offers mobile machinery, both dewatering screw presses and Class A Bioset systems, that Utilities can purchase and move between their plants to support operations during various outages. The units are also available through another firm called SBI Rents that offers these units as part of its rental fleet. In the case of Palm Coast, SBI Rents was able to provide its mobile FSP 1103 screw press, and its field service personnel were able to select an appropriate polymer, fine tune its operation, and spend one-on-one time training the operators on how to use the equipment.
Plant operators have been impressed by several facets of screw press operations, most notably that the screw press rotates at less than one rpm and is very quiet to operate. Their experience is working around a centrifuge that rotates at high rpm’s and requires hearing protection while in operation. Another feature that has impressed staff is that it only has one wear part and the normal plant maintenance staff can replace that without sending the unit out for repair. That one wear part is the sealing lip on the flight of the screws that needs to be replaced about every 8000 hours.
Also, one of the biggest surprises to the operators was the daily uptime on the machine. With their centrifuge they lose over an hour of time filling the machine with solids at the beginning of the day and evacuating the solids from the machine at the end of the day. With the screw press, the biosolids remain in the machine on shutdown, so while in auto operation, the operators basically push start at the beginning of the shift and push stop at the end of the shift. This allows the operators to run the machine unattended during the day, enabling them to tend to other plant duties as required.
SBI has the ability to manufacture multiple size mobile screw presses for any operation that requires dewatering. Between SBI and SBI Rents, we can provide a solution for your emergency or normal day-to-day operations.
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