Lawrence Street Water Pollution Control Facility

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The Treatment Plant

The Lawrence Street Water Pollution Control Facility (LSWPCF) is designed for a peak hour capacity of 18.0 Million Gallons per Day (mgd) with a peak daily flow of 12 mgd through the biological treatment system.  The average day capacity of the facility is 10 mgd.  The LSWPCF was originally constructed in 1939 as a trickling filter plant in conjunction with a system of interceptor sewers to serve the Hocking River and Baldwin Run/Ewing Run areas.  The plant was expanded in 1965 and again in 1985, 1992 and 1997 to meet the demands of a growing city and increased regulatory requirements.

National Pollutant Discharge Elimination System (NPDES) Permit

Effluent from the Lawrence Street Water Pollution Control Facility discharges to the Hocking River in accordance with the NPDES Permit issued by the Ohio Environmental Protection Agency.  Discharge limits were developed based on chemical and biological data and modeling and in accordance with the Hocking River Total Maximum Daily Load Report as developed by the Agency.

Monthly Average Effluent Limits are

Total Suspended Solids (TSS)   12 mg/l
Carbonaceous Biochemical Oxygen Demand (CBOD) 10 mg/l (summer) 5.5 mg/l (winter)
Ammonia Nitrogen 1.4 mg/l (summer) 2.1 mg/l (winter)
Disinfection (summer only)
     E. coli 126/100 ml
    Chlorine 0.21 mg/l Maximum

 Dissolved Oxygen (DO) Minimum 6.0 mg/l
WPC 10
The Treatment Process

Influent Screening-Bar racks and screens remove large solids and debris

Grit Tank-Heavy sand like material is removed by settling

Raw Sewage Pumping-large screw pump move the effluent from the grit tanks

Primary Settling Tanks-Inorganic solids settle in these tanks to become primary sludge

Equilization Tanks-Under peak conditions excessive flows are diverted to the Equalization Tanks where it is held until the flows drop.  The wastewater is then fed back to the raw sewage pumps.

Tricking Filters-Effluent from the primary settling tanks enters the rock media Trickling Filters which is the first phase of the biological treatment.

Activated Sludge-The second biological treatment is conventional aerobic activated sludge to provide additional removal of organic material

Disinfection-During summer months chlorine is used to kill pathogens in the effluent.  Excess chlorine is removed through Dechlorination.

Post Aeration-The final effluent is aerated before it is pumped to the Hocking River.  This last shot of oxygen raises the Dissolved Oxygen levels for aquatic health.

Primary Sludge-The solids that are removed in the primary clarifiers are thickened before being sent to the Anaerobic Digesters for treatment.

Secondary Sludge-The solids from the tricking filters and the activated sludge aeration tanks are thickened and stored for later treatment.

Lime Stabilization and Land Application-The sludge goes through one final step of Lime Stabilization to neutralize pathogens before it is land applied as a fertilizer on local farm fields.