Intermittent sand filter secondary treatment 1 7

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Intermittent sand filter (Secondary Treatment).
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1-7 Introduction to Wastewater Management treating the liquid wastewater. Proper solids handling is of paramount importance. If sludge is not removed, problems will occur in other areas of the plant. Excess solids can also lead to State Pollution Discharge Elimination System (SPDES) Permit violations and odor problems. There are many different options available for solids handling. Local conditions usually dictate which option is best for your particular facility. General categories of sludge handling include digestion processes, hauling of liquid sludge to a larger treatment plant, thickening, dewatering by mechanical means (belt filter presses, centrifuges), incineration, land filling, and land application. The Herkimer County Wastewater Plant is designed for 6.1 million gallons per day (mgd). Sludge is pumped to a gravity thickener, treated to reduce odors, and dewatered using a belt filter press. The dewatered solids are treated using dry lime for stabilization and loaded into a roll off container. A contractor takes the container and stores the solids. The sludge is later land applied on crop fields. The City of Little Falls Wastewater Plant is a 5.0 mgd design and pumps the sludge to a gravity thickener. Solids are dewatered using a belt filter press and then incinerated. The remaining ash is landfilled. The Village of Clinton Wastewater Plant is a 2.5 mgd design that gravity thickens the sludge before pumping into an anaerobic digester. In the past, solids removed from the digester were pumped to a drying bed and landfilled. The drying beds were troublesome due to weather dependency e.g. rain and winter. Solids from the anaerobic digesters now go to a belt filter press, and then to a landfill. The Old Forge Wastewater Plant (0.45 mgd) pumps the sludge to an aerobic digester. When the digester approaches capacity, the solids are then treated with polymer and processed through a thickening device. The solids are stored in another aerated tank until it is time to call for a tank truck. A contractor hauls 6,000 gallons to the Watertown Wastewater Plant for further treatment and disposal. In summary, there are many options available for sludge treatment and handling. Where does the water go after treatment? The treated wastewater is referred to as effluent. The effluent is discharged to a water body such as a lake, river, stream, or groundwater. Conditions contained in the SPDES Permit are designed to minimize the Sand drying beds can be problematic, particularly with rainy conditions.
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1-8 Handbook on Wastewater Management impact that the effluent may have on the receiving stream. Small streams that have a classification of trout spawning or that are used downstream for drinking purposes have more stringent (tighter) permit limits than streams that discharge into a water body with a higher flow and/or sizeable tributaries.
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