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Newville, Pa., facility uses treatment system to save electricity, meet effluent criteria
The Newville Borough Water and Sewer Authority (NBWSA) in Newville, Pa., has over 6.5 miles of sewers in the borough, serving a population of 1,326. An additional 5.7 miles of gravity sewers and one pumping station serves surrounding municipalities.
The NBWSA and its consulting engineer determined that to meet anticipated effluent criteria required by Pennsylvania Department of Environmental Protection, the existing wastewater treatment facility would be converted for aerobic sludge digestion and storage. Also, a new wastewater treatment facility would be constructed to meet the future organic and hydraulic capacity needs of the authority and the Chesapeake Bay watershed nutrient loading limits proposed for existing wastewater treatment discharges.
As a safety feature, there is no floating equipment within the SBR basins. All equipment is mounted to the tank walls and can be maintained without entering the basin. The tanks’ fine bubble diffuser grids are mounted to the basin floor, but unlike a true batch SBR system, the ICEAS process can operate using a single basin without process modifications or effluent degradation. This allows a basin to be drained for maintenance, if necessary.
The new facility is equipped with mechanical mixers, in-tank dissolved oxygen sensors and VFD-controlled blowers so that aeration can be controlled by the dissolved oxygen concentration in the basins during the react period of the treatment cycle; this prevents overaeration during aeration periods of the react cycle, allowing the dissolved oxygen to quickly crash during anoxic periods in the cycle. Alternating periods of oxic react and anoxic react generate nitrate and denitrify the nitrate created, respectively. Nitrogen gas produced by denitrification is stripped during a final aeration period prior to settling.
In addition to a superior effluent, the new facility has experienced operational savings.
A 20 to 25% reduction in electricity costs was realized almost immediately after startup due to the dissolved oxygen concentration control system and the recovery of oxygen from the denitrification process. Another advantage of the process is its operator-friendliness. With no return or recycle pumping to adjust, the only typical adjustment required is the waste sludge wasting rate (in order to maintain the target MLSS concentration).
Having the ability to treat total nitrogen below permit limits not only reduces energy costs by taking advantage of demand-only aeration and denitrification oxygen release, but it can also generate a new revenue stream in the form of nutrient credit trading. Unused nutrient allocations can be sold to other facilities that cannot meet their allocations.