Evaluation of an Economical Alternative Onsite Domestic Wastewater Treatment System to Remove Soluble and Particulate Organic Oxygen Demand
Abstract:The marshland upwelling system (MUS) was designed as an economical alternative onsite domestic wastewater treatment system for campsites in coastal areas of Louisiana. Domestic wastewater produced at campsites is equalized in a large primary distribution/collection tank then injected deep (3.05 m – 7.62 m) into the substrata marsh environment via a progressing cavity pump. The density gradient created between the fresh wastewater and the saline native groundwater provides the driving force to push the wastewater up through the marsh toward the surface. In theory, this is similar to an upside-down sand filter or vertical subsurface flow wetland. Bacterial pathogens are removed from the wastewater through physical straining, adsorption, and predation via the natural soil matrix. Over time, fixed-film anaerobic bacteria develop in the marsh substrata soil environment and break down the soluble and particulate organic matter in the injected wastewater, complementing or increasing the removal rate of bacterial pathogens through biofilm development. Although the majority of the solids (60–80 %) are removed in the primary wastewater distribution/collection tank through settling and floatation, a considerable amount of suspended organic and inorganic solids are injected into MUS over time. The organic solids degrade to soluble CBOD5 (sCBOD5) in the subsurface environment of the marsh. This has both a positive and negative effect on the system. Increased solid loadings to the MUS system decreases the hydraulic conductivity of the system over time by filling the interstitial pore spaces of the soil matrix, but the organic nature of the majority of suspended solids injected provides a continuous source of substrate needed to maintain a healthy and productive biological community. The slightly negative charge associated with the clayey soils of the substrata marsh environment provides excellent adsorption sites for the cationic pollutants commonly associated with domestic wastewaters (i.e. Nutrients - Ammonia).
Document Type: Research Article
Publication date: January 1, 2004
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