Groundwater Quality Impacts From the Storage of Sludge and Septage

Abstract: This study was undertaken to assess the possible migration of substances from a wastewater sludge storage lagoon to groundwater. Research indicates that volatile organic compounds (VOCs) may be present in domestic wastewater sludge and may migrate to groundwater. This study was conducted around the sludge storage lagoon owned and operated by Pat’s Sanitary Service, a septage/sludge hauling business located in southeastern Wisconsin. Pat’s collects septage from area septic systems and sludge generated at municipal wastewater treatment facilities. This material is stored in a clay lined lagoon until it can be spread on agricultural land. Based on the results of ongoing groundwater monitoring for inorganic substances at the site, Pat’s storage lagoon is considered to be leaking and impacting groundwater. For this study, samples were collected of the sludge material being stored in Pat’s lagoon and from site groundwater monitoring wells. These samples were analyzed for NPDES Priority Pollutants and three organic compounds were detected at the site. 2-Methylphenol and phenol were detected in the stored sludge material but not in groundwater below the site. Chlorobenzene was detected in one of the three facility monitoring wells sampled but was not detected in the stored sludge material. The levels of chlorobenzene detected in groundwater at the site were considerably lower than the Safe Drinking Water Act maximum contaminant level (MCL) of 100 UG/L. There is currently no Wisconsin state NR 140 Groundwater Quality Standard for chlorobenzene. Because only a limited number of samples were collected for this study it is difficult to draw definite conclusions, however, the sample results obtained do seem to indirectly support the concern that organic compounds can be present in stored sludge and septage material and that, if mobile, these substances may migrate to groundwater.