Ultimate Disposal

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Ultimate Disposal of Wastewater Sludges

Wastewater treatment plants must dispose of the residuals resulting from wastewater treatment. The most common disposal methods are incineration, land application, landfilling, and sale and distribution. Incineration is simply the controlled burning of the sludge with appropriate air pollution control equipment. Facilities using incineration do not normally use any other treatment process for the sludge, such as digestion. After the sludge is pumped from the sedimentation basin it has much of the remaining water removed and is then sent directly to the incinerator. Facilities electing to use incineration must obtain a Clean Air Act permit and meet stringent air quality standards. Due to the high costs involved with incineration and air pollution control equipment, only large municipalities can afford this option.

Land application is the application of the waste sludge either onto the surface of the soil or injected a few inches into the soil surface. Although crops can be grown on this land, the US EPA restricts the use to non-food production. The City of Carbondale uses this disposal method. Rather than buying or leasing land for this purpose, some municipalities elect to market and sell their sludge as a soil amendment. The sludge will add significant organic content and some nitrogen and phosphorus to the soil. Some municipalities make their sludge available free for this purpose.

Landfilling of sludge is also a common option. After treatment of the sludge, much of the water is removed and it is then transported to a local landfill for burial.

Typical disposal methods are shown in the two charts below.

Sludge Disposal at Small Plants

Flow is less than 10 million gallons per day or the population less than about 80,000 people

Sludge Disposal at Medium and Large Plants

Flow is greater than 10 million gallons per day or the population greater than about 80,000 people

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    Web posted 3/27/97