Ammonia Behaviour in Wastewater Reclamation by Soil Aquifer Treatment

Abstract

Groundwater use is increasing all over India and Chennai is not an exception. A good possibility exists to recharge artificially the excess treated wastewater through Soil Aquifer Treatment (SAT) and use the recharged water for purposes other than drinking. Soil column experiments were performed, in order to study the ammonia, nitrite and nitrate reduction from Real Secondary Treated Wastewater (RWW). SAT was simulated in four 15 cm long soil columns packed with soils of Sandy Clay Loam (SCL) texture collected from Anna University Sewage Treatment Plant (STP), Chennai, India. Soil Columns were ponded with wastewater to a depth of 2.5 cm above the soil surface and operated for a period of Ten cycles under 4 different alternating wet and dry cycles, 0.25 day wet/1.75 days dry (R1), 0.25 day wet/2.75 days dry (R2), 0.25 day wet/3.75 days dry (R3) and 0.25 day wet/7.75 days dry (R4). The effect of wetting and drying periods on SAT ammonia removal performance was assessed comparing ammonia, nitrite, nitrate nitrogen and TDS rates. The removal of ammonia was through nitrification process which is found to be a dominant removal mechanism of nitrogen. Nitrification differed according to the different drying cycle’s time with fixed flooding period. When the reduction performance achieved with different drying cycles were compared, it could be seen that longer drying periods with R3 column yielded with the least nitrate value of 0.58 mg/l. From this study, it was found that with the fixed wetting period, maximum drying period is required for nitrate reduction and minimum drying period is required for TDS reduction.