Management of Process Solids, Sludges, and Residuals
Solids, sludges, and residuals are generated during decentralized wastewater system operations. These materials need to be properly handled, appropriately treated and safely disposed of or beneficially used. This chapter describes the different types of s
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15-1. Scope Solids, sludges, and residuals are generated during decentralized system operations. These materials need to be properly handled, appropriately treated and safely disposed of or beneficially used. This chapter describes the different types of solids, sludges, and residuals that are often generated in decentralized systems and highlights options for treatment and disposal or use.
15-2. Key Concepts ■
A variety of solids, sludges and residuals can be generated during decentralized wastewater treatment and water reclamation. The quantity and character of these materials can be very important and may influence the selection, design and implementation of a decentralized system.
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The types of solids, sludges, and residuals that can be generated in decentralized systems include the following. • Process sludges and residuals are generated as a product or byproduct of the treatment processes that occur in many unit operations. ○ Septage includes settled sludge and scum that is removed from septic tanks periodically to maintain a desired hydraulic retention time. ○ Waste biological solids include waste activated sludge removed from aerobic treatment units and membrane bioreactors and biomass solids that slough off in recirculating porous media biofilters.
© Springer International Publishing AG 2017 R.L. Siegrist, Decentralized Water Reclamation Engineering, DOI 10.1007/978-3-319-40472-1_15
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Management of Process Solids, Sludges, and Residuals ○
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Granular media is used for biofilters and nutrient reduction operations and this media can become clogged or saturated with the constituents being removed and require disposal and replacement or regeneration and reuse. Vegetation grows in constructed wetlands and landscape drip dispersal units and it may be cut and removed from a site for aesthetic or nutrient removal reasons. The vegetation removed requires proper handling and disposition. In addition, vegetation can be grown in sites amended with wastewater solids and sludges and these sites can subsequently be used for grazing or as a food crop.
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Excreta solids, fecal sludges, and diverted urine can be generated in some situations and they need to be managed. ○ Excreta solids accumulate in waterless toilets and fecal sludges accumulate in vaults to which low-volume water-flush toilets discharge. ○ Urine can be generated in urine diverting toilets where this source separation approach is used. ○ The accumulated waste, and materials with resource values under the specific circumstances, need to be removed periodically. • In addition, there can be other materials that may have to be dealt with including: ○ Grease that is removed from grease interceptor units installed in kitchens at restaurants, schools, nursing homes and other food service operations. ○ Untreated wastewaters that are removed from holding tanks that are pumped periodically (e.g., every few days, weeks, or months) at sources where there is only seasonal use or where there is no option for local wastewater treatment and disposal/reuse
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