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Easterly Process Diagram
Easterly Treatment Plant
Glossary of Terms

 Easterly Process
Wastewater flows to the Easterly WWTP through three major sewer pipelines: the Collinwood Interceptor, serving the northeast portions of Cleveland; the Easterly Interceptor, serving the downtown Cleveland area; and the Heights-Hilltop Interceptor, serving much of Cleveland's eastern suburbs.

Preliminary Treatment

Two preliminary treatment processes remove particles and materials that could damage or plug plant equipment. First, mechanical screens prevent large debris from entering the plant. Second, grit removal removes heavy, abrasive material by settling.

Primary Treatment

Primary treatment makes use of the difference in weight (lighter or heavier than) between any remaining particulate matter and the water carrying it. In this process, wastewater flows into large settling tanks, in which the lighter material floats to the top (where it is removed by skimming) while the heavier material sinks to the bottom (where it is removed as sludge).

Through this process, 65% of the solids suspended in wastewater are removed. The scum skimmed off the top, along with similar material from the Southerly and Westerly WWTPs, is incinerated at Easterly. The biosolids (sewage sludge) pumped from the bottom of the tanks are sent to the Southerly WWTP for further treatment.

Phosphorous, an element commonly found in fertilizers and which can be harmful to lake Erie, is also removed during primary treatment. The addition of pickle liquor (ferrous sulfate) converts the phosphorous to a heavy particulate, which settles out of the wastewater. Overall, Easterly WWTP removes approximately 87% of the phosphorous from the wastewater, discharging less than 1 mg/l total phosphorous into Lake Erie.

Secondary Treatment

Secondary treatment consists of aeration basins and final settling tanks. The aeration basins provide the right conditions to grow "activated" microorganisms to remove fine particulates and soluble organic material that were not removed in primary treatment.

The microorganisms essentially feed on this material, converting it into new biological cell mass as they grow and reproduce. The microorganisms are separated from the clean water in the final settling tanks and then pumped back to the aeration basins to "activate" further growth. As the number of microorganisms increases due to reproduction, some must be removed from the system as waste activated sludge (WAS). The WAS is pumped to the primary settling tanks where it is combined with the primary sludge and then sent to Southerly WWTP for treatment.

Through the combined action of primary and secondary treatment, the Easterly WWTP removes greater than 95% of the incoming suspended solids and organic matter from the wastewater.

Final Treatment

The final treatment step is disinfection, comprised of two steps. The first involves adding chlorine, in the form of liquid sodium hypochlorite (essentially, concentrated household bleach), to the treated wastewater. This process kills most remaining organisms. A second liquid compound, sodium bisulfite, is then added to remove any leftover chlorine, which can be harmful to Lake Erie organisms. Disinfection of the plant's effluent occurs during the warmer months of May through October. The effluent is lifted by large screw pumps to an elevation that allows the water to flow into Lake Erie under all lake levels.
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