AERATED LAGOONS: NEWHALL MODEL FOR AMMONIA TREATMENT
Abstract:The Newhall, Iowa aerated lagoon system provides very good removal or oxidation of nitrogen even in winter and spring. The Newhall treatment facilities are a modified aerated lagoon system with 11.8 million gallon capacity in four cells but only the 2nd and 3rd cells are aerated. Newhall is a small town with about 1000 people but a very wet sewer system. The annual average flow is 0.165 mgd, average dry weather flow is 0.115 mgd, average wet weather is about 0.250 mgd, and maximum day flow rate is 1.60 mgd.
The lagoon system is operated with three different (winter, spring and summer) modes and flow paths with each providing optimum treatment and flexibility. Winter operation requires all lagoons operating in series, with maximum capacity, maximum water level and an average of 85 days total detention time. The 1st pond acts as a flow equalization basin and also works as a primary settling basin reducing CBOD and NH3-N by about 50%. With the very dilute wastewater, sedimentation in the first facultative lagoon and longer aeration time during winter, treated effluent ammonia in the spring is usually below 4-6 mg/L.
In spring, all raw wastewater still passes through all four lagoon cells in series. The water level in the first lagoon is lowered to half depth to help absorb shocks from excess spring flows. In summer, all raw wastewater is diverted directly to the aerated cells and the first cell is bypassed. Wastewater captured in the 1st lagoon cell during winter is pumped into the aerated cells for treatment at convenient times when there is extra capacity and warmer water temperatures. In late fall, all raw wastewater is diverted directly to the first cell again in preparation for winter.
Document Type: Research Article
Publication date: January 1, 2002
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