Case Study of Electrical Conductivity Control at an Industrial Wastewater Treatment Plant

Abstract

Tests were conducted to determine the feasibility for using nitrification and denitrification to control electrical conductivity in an industrial wastewater treatment process effluent. A laboratory-scale sequencing-batch reactor (SBR) system provided 98.5% COD removal and 99.5% nitrification when operating at a solids retention time of 12 days. The resulting average effluent COD concentration was 20 mg/L. Complete nitrification occurred within six hours of aeration but twelve hours of reaction time was required for denitrification. The nitrate-N concentration in the decanted SBR effluent averaged 21 mg/L. Completion of denitrification in downstream denitrification filters will reduce the EC from 1,210 to 852 μS/cm, thereby allowing the plant to meet its EC discharge standard.

Process Design Considerations for Industrial Wastewater Treatment Using SBR Technology to Achieve Biological Nitrogen Removal and EC Control

“…An internal model developed from referenced sources was used to assess the SBR requirements using information from treatability studies (EPA, 1993;M&E, 2003). Treatability studies confirmed the ability to achieve 98.5% COD removal efficiency and produce an effluent COD concentration of 20 mg/L (Young, et al, 2008). Additionally, nitrification was nearly complete (99.5%) resulting in an effluent quality with an NH 3 -N concentration < 1.0 mg/L.…”

“…Multiple studies were performed to evaluate the efficacy of using the existing anaerobic pretreatment units, evaluate the first stage aerated lagoon performance, quantify denitrification rate parameters and evaluate EC control alternatives (Young et al, 2008). The process flow sheet adopted for the facility is shown in Figure 2.…”

“…Since residual ammonium could be oxidized in downstream processes through nitrification and then reduced by denitrification to release N 2 , dissolved residuals would not remain to contribute to EC. Laboratory bench-scale reactors were operated for 77 days to verify that this option would meet effluent quality objectives and reduce the EC to acceptable levels (Young et al, 2008).…”

“…Therefore, treatability studies were performed using various amounts of raw and blended anaerobically and aerobically pretreated wastewater (Young et al, 2008). These tests produced the denitrification rates shown in Table 4.…”

“…Because EC is the combined effect of all dissolved ionized chemicals in the wastewater, any addition of chemicals by industrial contributors to the treatment plant will increase the EC. Chemicals used for pH control in the anaerobic pretreatment reactor also contribute significantly to the EC of the final effluent (Young et al 2008). …”