UTILIZING 'CLEAN' SAMPLING AND ANALYTICAL METHODS TO ESTABLISH SITESPECIFIC DATA FOR DEVELOPING INDUSTRIAL PRETREATMENT LIMITS

摘要

The U.S. Environmental Protection Agency requires that local regulatory authoritiesrnpromulgate limits for toxic compounds that are discharged to publicly owned treatmentrnworks (POTWs). Guidance from EPA requires a rigorous analysis whereby thernindustrial pretreatment limits are based upon the most stringent of the following threerncriteria: water quality of the receiving stream, interference and inhibition to therntreatment plant and sludge disposal criteria. The methodologies for establishing thernpretreatment limits are well known; however, applying "clean" sampling and analyticalrnmethods to collect the site-specific information to determine the industrial pretreatmentrnlimits is a recent innovation.rnIn 1998, DeKalb County developed industrial pretreatment limits for conventionalrnpollutants, metals and regulated organic compounds. A two tiered approach was usedrnto establish the limits. In Tier 1, the limits were calculated using existing data and EPArnGuidance Manual data. For this approach, the lead limit was 0.005 mg/L. In secondrntier, it was decided to collect site specific information for the lead concentration of thernplant influent and effluent and the domestic wastewater. It was necessary to utilizern"clean" sampling and analytical procedures because the previous studies usingrnconventional procedures could not detect lead in either the POTW influent, effluent orrndomestic wastewater. The detection limit using conventional procedures was 0.010rnmg/L.rnThe influent and effluent lead concentrations determined using "clean" sampling andrnanalytical procedures averaged 0.003 mg/L and 0.00017 mg/L, respectively. ThernPOTW removal averaged 94.5 %. The POTW removal was considerably higher thanrnthe removal rate of 52 percent reported in the EPA Guidance Manual. The net effectrnof a higher removal rate was to increase the allowable headworks loading for lead. Arnhigher headworks loading resulted in a larger lead allocation for industries whichrndischarged to the POTW. The lead pretreatment limit obtained by collecting sitespecificrndata by "clean" protocols was 2.64 mg/L which was considerably higher thanrnthe value (0.005 mg/L) obtained using EPA Guidance Manual data.