The last upgrade at the Maple Shade (N.J.) Wastewater Treatment Facility took place in the early 1990s. The plant’s bar screens are still cleaned manually and the aeration and mixing settings on the facility’s oxidation ditch system are set by operators based on incoming flow. Despite these challenges, the facility recently achieved the milestone of 10 years with no lost-time accidents.
And beginning this year, the facility will begin an upgrade of an expansion project to automate some systems as well as begin supplying reclaimed water for irrigation to a nearby golf course and recreational fields.
The 12,900-m3/d (3.4-mgd) facility is owned by the township but operated through a contract operations agreement with Woodard & Curran (Portland, Maine). The plant uses a multichannel oxidation ditch activated sludge process and discharges effluent to the South Branch of Pennsauken Creek.
Wastewater enters the facility through a static bar screen that filters out larger material that may clog downstream processes. Operators manually remove screenings and place them in 19-L (5-gal) buckets lined with burlap bags for dewatering. Next, the wastewater flows to the screw pump wet well. Three 22-kW (30-hp) screw pumps lift the wastewater to the splitter box.
The wastewater flows from the splitter box to the outer ring of the three-ring oxidation ditch system with four 30-kW (40-hp) aerators and two 56-kW (75-hp) aerators. The aerators operate on either fast or slow speed and are manually controlled by the operations staff to maintain adequate dissolved oxygen. The influent first enters an anoxic zone as it mixes with the mixed liquor in the tank. The anoxic conditions remove nitrogen and phosphorus. Nitrogen compounds (i.e., nitrates) are converted to nitrogen gas and released into the atmosphere.
The flow then proceeds to the aeration rings, where air is added to create an aerobic condition for the biological removal of organic matter, as measured by biological oxygen demand and total suspended solids reduction.
Mixed liquor flows to the secondary clarifiers, which are peripheral feed units. Sludge removed after settling is returned to the oxidation ditch process, and a portion is sent to the plant’s aerobic digester. The digester is supplied with two 30-kW (40-hp) blowers and a 30-kW (40-hp) mixer to stabilize and thicken the activated sludge prior to dewatering on the belt filter presses. The dewatered solids are hauled offsite in rolloff containers to the Burlington County Compost Facility.
After the secondary clarifiers, the effluent flows to two chlorine contact tanks where, upon entry, it is dosed with sodium hypochlorite. Following disinfection, sulfur dioxide is added to reduce the chlorine residual to less than 0.02 mg/L prior to discharge. Chlorination and dechlorination are flow-paced. The flow is measured with a rectangular weir, and the dissolved oxygen is raised with a mechanical aerator. The effluent is sampled with an automatic sampler.
Upgrades under way
Recently, the township approved a 10-year operations improvement plan to address the challenges the facility has faced. These challenges include improvements to enhance aesthetics; evaluate equipment, instrumentation, and controls; develop customer service plans for future construction; perform leak detection evaluations; and improve safety procedures.
More specifically, this year the township’s capital budget includes an upgrade of the facility’s pretreatment system, installing an automatic bar screen system, and replacing the three screw pumps. This work is expected to begin this fall.
Additionally, construction already has started on a beneficial water reuse project. The project will convert an unused, old sand filter to a disc filter system. The project is a cooperative effort with the neighboring community to supply irrigation for a golf course and recreational fields.
The township also is proceeding with plans to install solar panels at the wastewater treatment plant to offset a portion of its electric costs.
Drinking water, too
In addition to providing wastewater treatment, Maple Shade also operates 84 km (52 mi) of sanitary collection system with nine pump stations, as well as drinking water production and distribution facilities.
The utility manages two groundwater treatment plants with design flows of 13,600 and 7600 m3/d (3.6 and 2.0 mgd), five wells, and 88 km (55 mi) of distribution system. Personnel are crossed-trained to operate both systems and hold New Jersey Department of Environmental Protection licenses for wastewater collection and treatment, as well as water treatment and distribution.
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