Abstract
The feasibility of household level treatment of grey water with activated charcoal was performed using laboratory batch adsorption testing on locally available charcoal media. The study results indicated that the potential for removal of organic matter was significantly high for the high pH cloth wash water compared to the low pH kitchen wastewater which also contained non-adsorbed organics. The addition of ash considerably improved the removal and projected life length of adsorption media for kitchen wastewater treatment. The adsorption isotherms obtained were all modeled adequately using the Freundlich isotherm while the isotherm shapes display different types of adsorption for the different streams of grey water because of the heterogeneous nature of the adsorbates in grey water. The replacement life length of activated charcoal for single drum household level treatment ranged between 7 and 15 months. For family daily flow rates up to 400 lit/day, the replacement costs of a single drum charcoal per cubic meter of grey water treated were calculated to be below the current tariff levels for acquiring water in cities in Swaziland. A considerable part of the grey water pollutant can be removed through pretreatment by sorption alone such as by filtration through sand or other cheap media before adsorption. For complete household level treatment of grey water, a three-step treatment consisting of sand pre-filtration, activated charcoal adsorption and sand post-filtration are recommended.
Highlights
Grey water recycling has been practiced worldwide since the 1970s and is being increasingly considered as feasible option for providing readily available water for reuse at household level while at the same time providing environmental protection and water conservation [1]
As will be shown later, the adsorption of organics by activated charcoal shows a bias in favour of better adsorption at higher pH
The research study indicated that activated charcoal can remove over 95% of the organic matter from cloth wash water while the efficiency of removal of organics from kitchen wastewater ranges between 30 and 70%
Summary
Grey water recycling has been practiced worldwide since the 1970s and is being increasingly considered as feasible option for providing readily available water for reuse at household level while at the same time providing environmental protection and water conservation [1]. The pollutant load, such as the organic matter content of mixed grey water streams, may be comparatively low compared to the wastewater from toilets. By contrast grey water from the kitchen was reported to have COD/BOD5 ratio of only 1.2 These kinds of differences in biodegradability of grey water can pause a challenge to the task of treating grey water by biological means.
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