A non-partisan, neutral perspective supporting diversity in the color of water

Sunday, June 27, 2010

Comparison of Three Systems for Biological Greywater Treatment

Water, a free, online peer-reviewed journal just released an interesting article on biological treatment of greywater.

Abstract: Greywater consists of household wastewater excluding toilet discharges. Three systems were compared for the biological treatment of greywater at a similar hydraulic retention time of approximately 12–13 hours. These systems were aerobic treatment in a sequencing batch reactor, anaerobic treatment in an up-flow anaerobic blanket reactor and combined anaerobic-aerobic treatment (up-flow anaerobic blanket reactor + sequencing batch reactor). Aerobic conditions resulted in a COD removal of 90%, which was significantly higher than 51% removal by anaerobic treatment. The low removal in the anaerobic reactor may have been caused by high concentration of anionic surfactants in the influent (43.5 mg/L) and a poor removal of the colloidal fraction of the COD in up-flow anaerobic sludge blanket reactors. Combined aerobic-anaerobic treatment accomplished a COD removal of 89%, similar to the aerobic treatment alone. Greywater methanization was 32% for the anaerobic system and 25% for the anaerobic-aerobic system, yielding a small amount of energy. Therefore, anaerobic pre-treatment is not feasible and an aerobic system is preferred for the treatment of greywater.

Download the article here.

It reads like the Zen Rainman and the Greywater Gangsters (video on sidebar) were onto something with their aerobic treatment systems of kitchen sink wastewater using small ponds and aquarium pumps. The KISS principle and some common sense go a long way towards removing the "threats" from our greywater.

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