With a rapidly growing population and three lagoons nearly at capacity, managers of the Star Sewer and Water District in Star, Idaho, needed to increase their treatment capacity. Additionally, local regulators were encouraging the facility to improve the quality of plant effluent.
The city decided it was time for a major expansion and hired Keller Associates, a consulting engineer firm in nearby Meridian, to explore various technologies. The design team decided to install membrane bioreactors (MBR) as the secondary treatment process.
To ensure the MBRs operate efficiently and reliably, the design team also selected a robust fine screen known as the Monster Separation System . The system ensures harmful solids and trash are removed, cleaned and then sent to the landfill before they have a chance to cause problems inside the MBR chamber.
Protecting Expensive Membranes
The Monster Separation System integrates a Bandscreen Monster with a Screenings Washer Monster to provide for the initial screening of solids, plus cleanup of the remaining discharged screenings by grinding, washing, dewatering, and compacting. The system was designed and manufactured by JWC Environmental of Costa Mesa, Calif.
“The membranes in the new MBR plant are expensive, and we wanted to be sure to have the best screening ahead of them so we don’t get grit or other material that could damage them,” explained Hank Day, maintenance and operations foreman for Star Sewer and Water District. “We also wanted to filter out as many total solids as we could, to keep the new MBR plant running at optimum capacity. This combination solids processing system allowed us to meet both objectives from the outset of the new plant operation. Anytime you’re dealing with wastewater, it’s a lot easier and cheaper to do it right the first time than to come back and add stuff later.”
The WWTP serves about 2,000 residential customers and another 25 commercial operations. The new MBR plant, featuring state-of-the-art flat plate membrane technology, opened in January 2006 and is expected to handle a surge in nearby residential construction and an increase in Star’s customer base. The lagoons were already filled to capacity.
“We’ve already gotten a big benefit with the aerators in our lagoons not plugging anymore,” Day said. “We had been pulling all nine of them for a day, ten times a year, for cleaning. We haven’t had to do that at all since we installed the Monster Separation System .”
Keeping the Operation Simple
At the WWTP’s headworks, a manual bar screen removes rags and other large material. The flow then moves through a grit separator, which deposits to a 3 cu yd (2.3 cu m) dumpster. The remaining wastewater then enters the Monster Separation System (MSS).
First, the Bandscreen Monster uses 2 mm perforated, ultra-high molecular weight plastic panels to capture and remove solids such as hair, trash and plastics. Next, the integrated Screenings Washer Monster (SWM) grinds, washes, dewaters and compacts the solids, turning the discharged screenings into a dry and nearly odor free “cake,” which is then dropped in the grit dumpster ready for disposal. The SWM's dual washing systems liquefy soft organics and return it to the plant flow.
The Cleaner Screenings Requirement
“The dumpster, which took about a month to fill up with ground material, now gets emptied every two weeks, only because we also fill it with trash,” Day said. “The cleanliness of the discharged solids (from the SWM) allow for hauling to a sanitary landfill, which was a compliance criterion that was assured by our engineers, Keller Associates.”
“We wanted to make sure organics were removed to reduce odor and ensure waste would be accepted at the landfill,” added Randy Zollinger, project manager for Keller Associates. “During our initial start-up we saw our decision to utilize the Screenings Washer Monster was justified as very little odor was generated from the washed and compacted screenings.”
“The JWC unit has been working fine. We check it daily, along with the rest of the plant, for cleanliness and neatness, and that’s all we’ve had to do,” Day added.
Clifford Seth is a professional writer. For more questions regarding JWC, please email [email protected] or call 949-833-3888.