The application of a solar still in domestic and industrial wastewater treatment

• A stepped type solar still is investigated experimentally under outdoors conditions.
• Distilled water quality results from different types of wastewater are discussed.
• The stepped solar still is successful in removing inorganic and organic contaminant.
• The still was also successful in removing bacteria.

A study on the treatment of sanitary and industrial wastewater by solar still was conducted in Malaysia by UKM (Universiti Kebangsaan Malaysia) University during November and December 2011 and January 2012. The experiment was performed by feeding three types of wastewater into a solar still. The pilot-scale solar still consisted of a stepped type solar still with an effective area of 0.8 m2. The characteristics of the raw wastewaters indicated that the chemical oxygen demand (COD) was high at 425 mg/L for sanitary wastewater and 2650 mg/L for diluted industrial wastewater and that the maximum turbidity was between 150 and 820 NTU (Nephelometric Turbidity Units) for both types of wastewater. The results showed that the condensate COD was between 2 and 86 mg/L for the different types of feed. The COD removal efficiency of the still was greater than 86.83 ± 3.45%. It was shown that the condensate quality in terms of total dissolved solids (TDSs), total suspended solids (TSSs), COD and turbidity matched the quality of high-grade water and it is suitable to discharge to surface water. The method was also successful in removing bacteria. Heterotrophic bacteria counts were enumerated to determine the inactivation percentage of HPC (Heterotrophic plate counts). A reduction greater than 86.75 ± 10.88% for HPC was achieved.

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