DEVELOPMENT OF PRETREATMENT LIMITS FOR FORMALDEHYDE INTEGRATING POTW TREATABILITY AND DERIVATION OF WATER QUALITY CRITERIA

Resulting from 1987 modifications to the Clean Water Act, water quality criteria were adopted for numerous elements and compounds with direct application to NPDES discharge limits. However, various compounds were not assigned criteria despite widespread use and perceived or real toxicity. In this case study, stringent pre-treatment limits for formaldehyde were imposed from an industrial discharger. The basis of these limits was:Utilization of a conservative water quality criterion given little toxicological data for formaldehyde,A lack of understanding of the effectiveness of biological treatment of formaldehyde, which was compounded byDeficiencies in low-level formaldehyde chemical analysis.This 18 month project was performed as part of an administrative order in this paper facility/s pre-treatment permit. Interim formaldehyde limits were included in the permit, and the goal of the study was to develop final permit limits for the facility which discharged between 300,00 and 400,000 gpd to a 1 mgd POTW.The project was initiated with research of formaldehyde analytical techniques and final utilization of a NIOSH methodology as the most repeatable and representative. This methodology appeared to eliminate the numerous false positives which were found in previous efforts for this discharger. Utilizing this methodology, a year long assessment of the pre-treated discharge, POTW headworks, and POTW effluent loadings was undertaken. Data gathered for this effort was concentrated in the first six months of the study with reduced frequency sampling undertaken for the last six months.A series of POTW effluent ‘non-detects’ was observed. This differed markedly from previous POTW assessments and was believed to be more representative than previous results due to the degree of QA in chemical method selection, the repeatability of results, and the results of split sampling and analysis. The POTW was observed to treat the formaldehyde nearly completely within a wide headworks loading range.In a separate effort, refined water quality criteria were developed which were used to calculate final permit limits for this discharger, integrating the effectiveness of biological treatment and these relaxed criteria. Lastly, a technology assessment was performed which showed that few technologies were available which could dependably reduce formaldehyde inside the complex paper facility waste stream matrix. Cost analysis was performed that showed that these pre-treatment steps were typically an order of magnitude more expensive than available POTW treatment. Integrating the results of the study and pre-treatment concept design, final limits were proposed and accepted by the regulatory agency which ended a long, contentious permitting struggle.