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Updated January 2003 Appendix E Laboratories using chromic acid for cleaning laboratory glassware should begin to abandon the practice as soon as possible for two reasons. First, the City of Stillwater has placed limitations on the concentration of chromium in wastewater discharge (1 mg/l hexavalent chromium; 5 mg/l total chromium). Second, the costs for proper treatment and disposal of the spent cleaning product can be expensive and shall be avoided, if possible. Spent (waste) cleaning products which contain potassium/sodium dichromate in sulfuric acid or the product Chromerge shall not be discharged into the wastewater treatment system; these materials shall be collected, marked & labeled, and disposed of as a hazardous waste. Therefore, due to the difficulties involved in treatment and disposal and management of spent cleaning solutions, the OSU Environmental Health Services Department Hazardous Materials Section recommends the following: Laboratories should seek alternative glassware cleaning solutions for products to meet their needs. Glassware cleaning products which do not contain chromium such as Nochromix are readily available and are recommended. Nochromix mixed with sulfuric acid is as effective as Chromerge in removing trace metals and enzyme residues, but it eliminates the need for special handling caused by the toxicity of Chromerge. In fact, spent solutions of Nochromix can be safely disposed of (after elementary neutralization) via the sanitary sewer if not contaminated with other metals or toxic substances. The cost of Nochromix is approximately one-third of that for Chromerge. Similar substitutes might also be available from other manufacturers. Purchasers of reagents and chemicals for the affected laboratories should determine if their suppliers can provide such environmentally suitable glassware cleaning agents. As an alternative to a sulfuric acid bath, a 95% Ethanol/Hydrochloric Acid bath or 95% Ethanol/Potassium Hydroxide bath can be used effectively against organic residues. (Caution: This procedure may etch glassware.) In cases where it is imperative that glassware must be cleaned using a cleaning solution containing chromium, the spent cleaning reagent is classified as a hazardous waste. This procedure will also be considered a special procedure (see Section 8.2 - "Special Procedures"). Please convey this information to persons in your area who may utilize chromic acid cleaning solutions. Your cooperation is this matter is solicited to help minimize the costs of disposal for regulated wastes. Please contact Environmental Health Services, Hazardous Materials Section, if you have any questions.
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