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Spring 2013 TREATMENT OF LABORATORY WASTE 111 Scientific, Scottsdale,AZ) calibrated daily as necessary, staff tested the pH of the waste formalin. Treatment of solutions with a pH<4.1 did not proceed until the pH was increased to near 7 with sodium borate. The pre-treatment pH of the waste formalin batches ranged from 5.2 to 9.9,with a mean of 7.5(n=706,SD=0.78). For treatment of—7.6 liters of 5%formalin(1.85%formaldehyde),we used one and a half of the 0.75 kg Neutralex®pouches (1.13 kg), while for treatment of the same quantity of 10% formalin (3.7% formaldehyde), we used two Neutralex®pouches (1.50 kg). After the appropriate amount of Neutralex®was added to the treatment container,the container was capped,shaken to mix thoroughly,and placed in a tray under the sink with a "Neutralex Added"sign. The date,volume and percentage of formalin,pre-treatment pH, and employee's initials were recorded on a treatment log next to each hood. We let the treatment container stand for 30 to 60 minutes during neutralization, and then moved it back to the fume hood, swirled or otherwise mixed the solution, and tested the pH and residual formaldehyde of the treated solution. We used EM Quant® formaldehyde test strips(product number 10036-1;EMD Millipore,Billerica,MA),which were semi-quantitative with a scale of 0- 10-20 -40 - 60 - 100 ppm; the test strips and reagent were stored in a refrigerator between use,per the manufacturer's instructions. A 5-ml sample of the treated waste was removed with a pipette and placed in the vial supplied with the formaldehyde test kit. Ten drops of the reagent were added to the vial and the vial gently swirled to mix. A test strip was dipped into the vial for one second,removed, and the long edge placed over a paper towel. After exactly one minute,the color on the test strip was matched to the color on the label of the test strip container. If the resultant formaldehyde concentration was>100 ppm,the waste solution was retreated. The resultant pH and formaldehyde concentrations were recorded in a log. The pH of treated batches ranged from 4.1 to 10.5,with a mean of 6.3 (n=706,SD=0.85). Residual formaldehyde of all treated batches tested at 0 ppm,although actual values potentially were>0 ppm because the lowest values of the test strips were 0 and 10 ppm. Finding that waste formalin solutions with pre-treatment pH ranging from 5.2 to 9.9 could be successfully treated with Neutralex®is noteworthy,because California Department of Toxic Substances Control (DTSC) field demonstrations of Neutralex® treatment at several health-care facilities used neutral-buffered 10% formalin with a pre-treatment pH near 7(DTSC 1997). Our post-treatment pH range of 4.1 to 10.5 was also broader than the post-treatment pH range of 5.5 to 7.75 reported from these demonstrations(DTSC 1997), likely because of how we buffered or otherwise adjusted the pH of our formalin solutions, variations in sample to formalin ratio,and variations in preservative age. DTSC certified Neutralex"as a hazardous waste treatment technology for use by the health-care industry,in part is based on field demonstrations at several health-care facilities. The CDFW process of waste formalin treatment with Neutralex®resulted in formaldehyde concentrations of<10 ppm,consistent with findings from those field demonstrations(DTSC 1997). LITERATURE CITED DTSC (DEPARTMENT OF TOXIC SUBSTANCES CONTROL). 1997. [Internet] Final notice of certification. Scigen Neutralex technology for treatment of aqueous formaldehyde wastes from the health care industry;[cited 29 March 2013]. Available from:www. dtsc.ca.gov/TechnologyDevelopment/TechCert/scigen-batch-treat-formaldehyde- techcert.cfin