An oxidation ditch plant consists of preliminary treatment and secondary treatment without...

An oxidation ditch plant consists of preliminary treatment and secondary treatment without a primary clarifier, as shown in Figure 11-30. Chlorinated effluent is discharged to a river. Solids are digested by aerobic digestion and hauled to land application.

Operating conditions:

Max. month design flow = 2.4 mgd; peak flow = 4.2 mgd; mini, flow = 1.3 mgd

BOD = 260mg/l, suspended solids = 210mg/l, ammonia = 25 mg/l Wastewater temperature = 17.5°C

Effluent treatment requirements:

BOD = 10 mg/l, suspended solids = 10 mg/l, 200 MPN/100 ml

Treatment units:

Influent pumping station wet-well dimensions 15 × 20 × 12 operating range of 8 ft; five pumps 3000 gpm each

Bar screen with  in. Openings

Grit removal—none

Final clarifiers—two at 60-ii diameter, 12-ft side water depth each

Oxidation ditch—lour with a volume of 80,000 cu ft, four brush aerators in each tank, MLSS = 2000 mg/l, sludge age = 15 days

Recirculation pumping station—six pumps at 300 gpm each

Chlorine contact basin—four passes in channels 20 ft long, 10 ft wide, and 10 ft deep.

Aerobic digesters—four units at 50 ft × 50 ft × 15 ft water level

Determine the operating characteristics for each of the treatment units and compare against the unit process design parameters listed in the text:

For the influent pumping station, determine the adequacy of the wet-well volume and pump sizes.

For the bar screen, determine the maximum screenings removal.

For the clarifiers, determine the adequacy of the overflow rates, weir loading, and detention times.

Will the sludge settle well?

For the oxidation, check the BOD and hydraulic loading. Check the aeration capacity.

For the chlorine contact basin , determine the detention time, chlorine feed rate in pounds, and amount of chlorine needed for a 30-day supply.

Calculate the sludge production and volume.

For the aerobic digesters, determine loading, detention time, and storage time.

For land application, determine the land area required using 30 mg/l nitrogen in the liquid sludge.

Will the treatment plant meet effluent requirements?