Shelton CT Operations Assistance

I began working for Maguire Engineers and the Shelton Water Pollution Control Authority (WPCA) by doing a preliminary operations review on May 16, 2009. After preparing a written report and reviewing my findings with the WPCA several weeks later, it was decided to have me spend a few months working with staff on some solutions to the ongoing operational problems. The major challenges facing the WPCA and the staff was unpredictable nitrogen removal and uncontrolled cost relating to the operation of the facility. After having spent a full month of working directly with the staff, which included 9 days on site so far, the following challenges were identified:

• Recycle loads from the sludge thickening process were overloading the plant with BOD and TN
• Odors associated with sludge handling were creating a nuisance in the neighborhood and needed to be controlled
• Numerous issues related to the SBR operation were identified including air flow meters that were not reading correctly, clogged decant valves from accumulated debris, and poor biomass quality related to widely fluctuating F:M.
• Consumable costs related to supplemental bacteria, polymer use and enzymes were becoming a burden for the WPCA

As a result of the initial findings, the highest priority item was to get the sludge thickening operation under control. The waste sludge holding tank was typically operated at over half full and without the ability to aerate the tank, anaerobic conditions were created which impacted sludge thickening efficiency, odors and filtrate quality. The sludge holding tank was emptied and now the staff keeps the tank empty daily. This significantly reduced the BOD and TN loading on the SBR's and allowed the staff to eliminate one of four SBR's from operation. Odors have also been reduced significantly.

It was apparent the SBR's had accumulated large amounts of debris (screening) as a result of the headworks barscreen being out of service for several months. The WPCA funded the cleaning of the SBR's which is now in progress. When the first of four SBR's were cleaned, twelve out of fifty decant valves were fouled with hair and rags. This contributed to the poor performance of the SBR's . Once the SBR was emptied, the decant valves were cleaned, all mechanical equipment was inspected and tightened and the SBR placed back on line. The remaining three SBR's will be cleaned over the next month and the plant will continue in three SBR mode going forward.

As a result of these changes to the operation of the plant it is expected the WPCA will save significant dollars on power, consumables and avoid paying nitrogen fees to the State. Once I have some firm figures, I will post the anticipated cost savings.