Influence of intermittent infiltration of primary effluent on removal of suspended solids, bulk organic matter, nitrogen and pathogens indicators in a simulated managed aquifer recharge system

• Intermittent application of primary effluent in managed aquifer recharge was simulated.
• Two hydraulic loading rates were used and the length of drying period was varied.
• Removal of bulk organic matter and suspended solids was independent of drying period.
• Significant removal of nitrogen and indicator microorganisms was observed with drying length.

The impact of intermittent application of primary effluent on the removal of suspended solids, bulk organic matter, nitrogen and pathogens indicators during soil aquifer treatment was investigated using 4.2 m high laboratory-scale soil columns fitted with sampling ports along the depth. Continuous and intermittent modes of application were adopted using peristaltic pumps to deliver the primary effluent to the columns operated at hydraulic loading rates of 0.625 and 1.25 m d−1 with varying wetting and drying periods. Experimental results exhibited insignificant change in suspended solids and dissolved organic carbon removals under continuous and intermittent mode of primary effluent application. While the overall removal of suspended solids ranged from 86 to 95%, the overall removal of dissolved organic carbon ranged from 50 to 60% irrespective of the length of wetting and drying period or the hydraulic regime. Nevertheless, reduction of ammonium-nitrogen varied significantly with the length of drying period and the highest reductions of 88.4 ± 0.8 and 98.0 ± 0.1% were achieved at 3.2 days wetting/6.4 days drying and 6.4 days wetting/6.4 days drying, respectively. Likewise, the removal of E. coli and total coliforms increased significantly with the increase in the drying period resulting in more than 4 log10 units under similar operating conditions. These results suggest that while removals of suspended solids and dissolved organic carbon were independent of mode of effluent application, removals of nitrogen and pathogens indicators were dependent on the length of the drying cycle.

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