New Septage Receiving System Ends Pump Clogging In Processing Plant

April 8, 2003
Problem Solvers

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Management at Stewart's Septic Services in Bradford, Mass., a privately held regional septic pumper for both residential and commercial tanks, reports it has taken advantage of a new septage receiving system to end the problem of clogged pumps in its processing plant. The move increased company income by enhancing its own processing capability, while allowing for increased collection activity and processing throughput.

The Honey Monster(TM) Septage Receiving System, which grinds, washes, and dewaters, was designed and manufactured by JWC Environmental of Costa Mesa, Calif. JWC also has successfully installed it at nine municipal sewage treatment facilities in the United States and Canada.

"Solids in the septage were previously clogging our effluent and grinder pumps left and right, as much as 20 times a day," recalled John DiVincenzo, the company's owner. "They required constant attention to pull off bottom plates and clean them up. We've expanded our collection reach considerably, and have plans to do more, and we knew we had to become more proficient in handling the septage deliveries and processing."

"The only maintenance we've had is changing the brushes after six months of operation, a task we did in about four hours without having to endure a shutdown. We estimate it will take us only about two hours the next time," he added.

Stewart's fleet of tanker trucks pump 60-100,000 gpd of residential (85 percent) and commercial (15 percent) septage, exclusively from septic tanks, in four states. His own 50,000 gpd, municipal-permitted processing operation is the primary recipient, with the balance delivered to independent processing plants ranging from 30 to 100 miles away. Solids included in the septage include heavy loads of plastic, textile, rubber, and other "floatables."

Founded in 1954 strictly as a pumper, Stewart's encountered increasing difficulty in finding local dumping opportunities by the late 1980s. Accordingly, the company established its own 10,000 gpd processing facility in 1994, by taking advantage of the already existing treatment plant in a former tannery across the street. The permit was later upgraded to 25,000 gpd, and then to the present 50,000 gpd in 1998. Stewart's hopes to gain permitting for 150,000 gpd by next spring.

In addition to the efficiency gains, the new system allows the company to keep more money by processing waste itself instead of paying to have it done elsewhere. It also gains the advantages of controlling its own processing schedule, and adding income through input received from other treatment plants.

Stewart's processing plant consists of four 15 ft x 20 ft, 20,000 gal. settling tanks that lead to a 15,000 gal. city bay. Septage moves through a 4" diam., 15" deep filtering baffle at the top of each tank, progressing through 100-mm and 300-mm openings. Eight-foot depth in the first tank drops to 6 ft by the fourth. Treated septage passes through a weir at the city bay into the municipal system. Grab samples are taken at the weir to assure compliance with city regulations of 800 mg/l for TSS, 750 mg/l for BOD, 100 ppm for oil and grease, and pH of 6-9. In addition, metals are sampled monthly.

The entire load for the plant first moves through the Honey Monster, except for grease, which is collected in 40,000-gallon holding tanks for separate disposal.

In previous efforts to deal with the solids problem, the company had originally tried a raking system, featuring manual raking over a grate as trucks dumped their loads into a 1000-gallon receiving tank. They added a rotary screen next to the raking system after they installed the settling tanks.

JWC Environmental says its system's unique combination of grinding, washing, and dewatering septage waste can be accomplished in 5 to 15 minutes for a typical septage truck. Dual-shafted grinding maximizes surface area on solids, facilitating cleaning, while two dual-manifold wash water systems help break up soft organics, and provide for enhanced dewatering with cleaner solids.

A high-level ultrasonic sensor and modulating plug valve regulates flow into the system and prevents overflow conditions. If the billing option is installed, flow into the system is measured by a magnetic flow meter, and the data is sent to the controller to create a billing record.

Equipment dimensions can be varied to suit particular installation requirements. Typical maximum flow is 600 gpm (137 cu.m./hr), and typical screenings capacity is 90 cu. ft./hr (2.55 cu.m./hr.).