An activated-sludge plant consists of preliminary treatment, primary, and secondary treatm...

An activated-sludge plant consists of preliminary treatment, primary, and secondary treatment as shown in Figure ll-27n. Effluent is UV disinfected prior to discharge to the river. Solids treatment consists of thickening the secondary clarifier sludge; primary sludge is pumped directly to digestion. Sludge is digested in two-stage anaerobic digestion and dewatered prior to hauling to landfill.

Operating conditions:

Max. month design flow = 10.3 mgd; peak flow = 19mgd; mini, flow = 5 mgd

BOD = 210mg/l, suspended solids = 240mg/l, ammonia = 22 mg/l

Wastewater temperature = 17.5°C

Effluent treatment requirements:

BOD — 10 mg/l, suspended solids = 10mg/l, 2.2 MPN/100 ml Treatment units:

Influent pumping station wet-well dimensions 15 × 25 × 10 operating range of 6 ft; five pumps, 4000 gpm on variable-speed drives.

Bar screen with ' in. openings

Grit removal—two units 40 ft × 12 ft

Primary clarifiers—two at 65-ft diameter, 7.5-ft side water depth each

Final clarifiers—two at 90-ft diameter, 14-ft side water depth each

Aeration basins—-eight at 80 ft × 40 11 × 19 ft water depth; the fine-bubble diffusers are at a depth of 18 ft, MLSS = 400 mg/l, sludge age = 15 days.

Recirculation pumping station—six pumps at 3000 gpm each

Blowers—four blowers at 56,000 scifn, 150 hp

UV disinfection—four units operated in parallel Thickening—gravity belt, 96 percent solids capture, 4.5 percent thickened solids

First-stage anaerobic digester—40 ft in diameter by 12 ft below the landings, 2 0 - ft operating volume

Second-stage anaerobic digester—40 ft in diameter by 12 ft below the landings, 10-(T operating volume above

Centrifuge—two at 300 gpm each, 20 hr per day, 5 days per week operation

Sludge pumping distances and fittings are as follows:

Primary sludge: 420 ft, 16 plug valves, 1 check valve, 6 flow-through tees, 18 standard 90° elbows, one entrance and one exit.

Secondary clarifier sludge: 860 ft, 6 plug valves, 1 check valve, 6 flow-through tees, 10 standard 90° elbows, one entrance and one exit

Thickened sludge: 520 ft, 12 plug valves, 1 check valve, 8 flow-through tees, 22 standard 90° elbows, one entrance and one exit

Digested sludge: 1200 ft, 4 plug valves, 1 cheek valve, 6 flow-through tees, 16 standard 90° elbows, one entrance and one exit

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 grit unit, determine the maximum grit removal?

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

Will the sludge settle well?

For the activated sludge, check the BOD and hydraulic loading.

For the UV disinfection at 93 watts per lamp, what is the power required to meet discharge requirements?

Calculate the sludge production and volume.

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

For the centrifuge press, verify the feed rate and operating conditions.

For sludge pumping, determine the solids concentration, flow, and head loss.

Will the treatment plant meet effluent requirements?