Brushes continuously clean clarifier weir.

Dry storage for high-quality biosolids.

Ultraviolet disinfection eliminates chlorine. Please click on the images above to see a larger version in a new window.

At four a.m. a 60 horsepower Flygt submersible pump begins its work, ordered to help an identical pump handle an increase in flow.

The sewage grinder has been running all night along with several 7.5 horsepower Sutorbilt blowers that remove grit through an air pumping process. Nearby, a 220 gallon per minute transfer pump moves thickened sludge into aerobic digesters.

Three 50 horsepower Roots blowers supply oxygen to the digesters. Each of those blowers operates for three hours then takes a one hour break in a standby mode. A fourth blower remains available if needed.

In the "heart" of the treatment process, aerators for oxidation channels and motors to turn skimmers and rotating assemblies in the classifiers run continuously. Other components sit in standby mode, waiting for another time when they may be summoned back to service by sensors and relays.

In the final stage, a single bank of ultraviolet (UV) lamps is on duty at this hour. This light instantly changes the DNA in the bacteria, thus preventing them from reproducing. Five other banks of UV disinfection units can come on line if they're needed to handle the flow through the plant.

The equipment in this plant has functioned normally through another typical night -- supervised by computerized process control equipment that unblinkingly watches key components ready to dial the phone for human help if anything fails to meet preprogrammed operational criteria.

Treatment plant operations require highly skilled staffing. Laboratory experts monitor the progress and performance of the treatment process and fulfill regulatory requirements while operators and maintenance staffers keep the systems and equipment functioning or ready for service if needed.

The state-of-the-art process control system permits the Dover Township Wastewater Treatment Plant to operate around the clock with a staff half the size of that needed to maintain operations without computer assistance.

"While our process control systems require technically-qualified operators, we can maintain control of the plant and protect the township's investments here without a large staff," said Plant Superindentant Sophie Simon. "Without those process controls, we'd need twenty people or more to keep us up and on line."

At the start of every day, experts on the staff review computer screens for reports on overnight operations. Computer reports on anomalies lead to control adjustments or equipment repairs.

The staff also operates belt filter presses two or three days per week, pressing moisture from sludge to produce an exceptionally dry odorless biosolid that crumbles into a powdery texture between your fingers. This plant byproduct could one day be used to enrich cropland.

Designed by Buchart-Horn, the Dover plant serves a high development area north of York, protecting the environment with very high quality effluent into the Little Conewago Creek that flows to the Susquehanna River on its way to the Chesapeake Bay.

Construction began in spring of '96 to double the capacity of an existing 4 mgd plant on the Dover site to 8 mgd while also upgrading the headworks, process control systems, and the sludge processing system.

The headworks features a special biofilter that deodorizes the air from the raw sewage influent wet wells. That air is exhausted through two feet of gravel and two and a half feet of compost that's topped with pine bark wood chunks through a system that removes 80 to 90 percent of the odor from the wet well air exhaust.

Other improvements included a new operations building, new electrical power distribution through a 3,000 amp switchboard and an 800KW emergency diesel generator.

The design and construction also upgraded onsite safety and environmental quality through replacement of chlorine gas disinfection with an ultraviolet disinfection (UV) system and post aeration cascade.

The Dover plant is a nitrification facility, utilizing the oxidation ditch activated sludge process to eliminate ammonia nitrogen, which is toxic to aquatic life.

The Dover Township plant actually improves the water quality of the Little Conewago Creek. Effluent from the plant contains higher levels of dissolved oxygen and lower levels of organic matter than streamwater flowing past the site on Graffius Road. Proof of that water quality is visible under the effluent outfall, where thousands of minnows provide a feeding ground for larger fish.

The B-H design not only came in on time and on budget, it will save the township time and money down the road because the design will permit efficient conversion of the plant to a denitrification facility likely to be required by the Commonwealth of Pennsylvania in the future. Stub walls and knock-out panels were designed into the oxidation ditch so the township can easily convert the plant should Pennsylvania one day require nitrogen removal as expected.

B-H provided Dover Township with initial studies, design, bid, construction management, resident project representation and operational phase services. Construction phase services included construction inspection, technical support, shop drawing review, change order and claim processing, application for payment review, final completion inspection and equipment startup and operation assistance.

Plant modifications and expansion were completed on schedule in September 1997. Exceptional partnering between B-H, the owner and contractors resulted in keeping the project well under budget. The estimated construction cost of $12.5 million was held to an actual cost of $10.6 million.