First Built in 1940

The Manitowoc Wastewater Treatment Facility was originally built in 1940 for $980,000. This was a primary treatment plant consisting of primary settling tanks, a primary digester, a secondary digester and sand drying beds. Primary treatment plants typically remove 25-35% of the BOD and 40-60% of the suspended solids. BOD and suspended solids are two measures of the strength of the sewage. There were three subsequent upgrades to the original plant.

Upgrades

The first upgrade was in 1959 at a cost of $1,430,000. The major changes were the addition of high rate trickling filters, secondary sludge pumping and final settling tanks. This increased the capacity of the treatment plant and added secondary treatment to improve treatment and reduce pollution. Typical secondary treatment removes 85-90% of BOD and 85% of suspended solids.

The second major upgrade was finished in 1976 at a cost of $19,500,000. This project increased the overall capacity of the plant, improved the secondary treatment process, added more final settling tanks, and added a tertiary filter process to remove fine particles. In addition, phosphorus removal was also added to the treatment process.

The third upgrade was finished in 2001 at a cost of $20,300,000. Three previous structures were removed and replaced with a new building that incorporated the processes from these buildings. Improvements were made in the digester mixing, stack filter drives, rock filter pumping and sand filter operations. Belt presses were added to provide for flexibility in disposal of biosolids. Computerization of the treatment plant was a major component of the plant upgrade.

Separated Sewer System

Manitowoc has a separated sewer system. This means storm water is not combined with the sanitary sewage. All sanitary sewage from residences, commercial establishments and industry as well as industrial waste are treated at the plant. The treatment plant processes an average of 9.0 million gallons per day. Approximately 40% of this flow comes from Manitowoc’s industrial base.

Plant Design Parameters

Plant Design Parameters
Design Population		53,000
Flow Design (MGD)	Average Maximum 24 hour Peak hour	15.5 25.9 30.9
BOD (lbs/day) Average Daily, mg/l		37,500 290
SS (lbs/day) Average Daily, mg/l		28,400 220
P (lbs/day) Average Daily, mg/l		1,160 9
Effluent Limits BOD, mg/l SS, mg/l P, mg/l		30 30 1