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Manteca sewer plant burying less money
Manteca wastewater treatment plant operator Benjamin Abulencia looks over one of the sedimentary clarifiers. - photo by HIME ROMERO
Wet sludge – the solid byproduct of treating the 9.87 millions of gallons of wastewater Manteca generates each day – can cost as much as $200,000 a year to bury in a landfill.

Municipal wastewater treatment plant operators are whittling that cost down by as much as $60,000 a year by taking advantage of warmer weather in the summer to have the sun ray’s bake out enough moisture to take the water content down from 80 percent to 20 percent. As a result, the sludge trucked to the landfill during the summer costs less to bury and therefore reduces pressure to increase monthly sewer rates.

It is just one way municipal staff is working to find ways to reduce costs to ratepayers on top of cost savings processes that have been built into the $61.3 million treatment plant expansion that started construction in December 2003.

“City workers are committed to providing the best service for the best price,” noted Public Works Director Mark Houghton.

The city can’t use the sun to dry sludge in the winter so the moisture content is at about 80 percent when it is hauled to the landfill. The roughly 20 tons buried during the winter translates into $4,200 a week in tipping fees as landfill costs are based on weight.

Outdoor drying in the summer reduces that landfill cost to $600 a week.

It isn’t the only cost saving part of the process.

The use of expensive chemicals – specifically chlorine - has been greatly reduced by installing state-of-the-art ultraviolet light channels to kill off disease causing organisms. There are 16 modular banks of UV lights that contain 2,240 separate UV light tubes.

The process is much more effective as there is a 100 percent kill rate of bacteria that causes diseases. The trade-off, though, is higher power costs that push the energy tab for running the plant past $1.2 million year.

Manteca is working to reduce that bill with the goal of making the plant self-sufficient in terms of electricity by employing solar panels and a cogeneration unit to generate power by burning methane gas.

City staff is also working on plans to divert treated wastewater from being returned to the river to instead help irrigate everything from landscaping to parks. It would cut costs in two ways – by helping reduce No.1 use of expensive treated drinking water to irrigate landscaping and to avoid possible future state-mandated upgrades in treating water returned to the river including more extensive removal of salts.

Manteca currently uses agricultural wash water sent to the treatment plant site via a purple pipe from Eckert’s Cold Storage on Moffat Boulevard. There are some 191 acres of corn used as silage for dairy cattle that is irrigated with the Eckert’s water.

In addition, the city got clearance from the Central Valley Regional Water Quality Control Board to allow contractors fill water trucks at purple pipe hydrants near the entrance of the treatment plant off Yosemite Avenue. That way when dust control is needed during construction, it can come from recycled water and not from fire hydrants on the streets. That could save enough water during construction season to serve up to 300 households a day.

Manteca’s plant operators also will “store” effluent to allow as much of it to be treated a possible during off-peak hours for electricity use. In doing so, they have managed to cut Manteca’s power bills.