Design and Operation of Point-of-Use Treatment System for Arsenic Removal Bruce M. Thomson, M.ASCE 1 ; T. Jeffrey Cotter 2 ; and Joseph D. Chwirka 3 Abstract: A point-of-use POU system was designed and constructed using commercially available activated alumina to remove arsenic from drinking water. Testing with City of Albuquerque chlorinated tap water containing an average of 23 ug/L arsenic found that 1 L of adsorbent would provide water for direct consumption by a family of four for 435 days. It was estimated that the POU system constructed for this study could be sold for $162, and the arsenic adsorption columns were estimated to cost $4. A monthly cost to the customer of $10/month was estimated to purchase, install, and operate this POU system, assuming annual replacement of adsorption media cartridges. The implications of relying upon POU systems to comply with a new drinking water standard for arsenic are discussed. DOI: 10.1061/ASCE0733-93722003129:6561 CE Database subject headings: Arsenic; Abatement and removal; Potable water; Water treatment. Introduction The Safe Drinking Water Act Amendments of 1996 mandated that USEPA develop and promulgate a new maximum contaminant level MCL for arsenic by 2001 42 USC 300g-1 b as a result of concerns that the existing standard of 50 ug/L did not provide adequate protection of the public. A final MCL of 10 ug/L was published in January 2001 USEPA 2001. A new drinking water standard for arsenic will inordinately impact water utilities which rely upon groundwater because these systems generally do not provide any water treatment beyond simple chlorination and sometimes fluoridation. Thus, the need to treat arsenic will require construction and operation of new treatment facilities which would be costly and will create new and unfamiliar infrastructure for the utility to manage. Two investigations have found that the costs of compliance with the new arsenic standard will result in monthly costs ranging from a few dollars per month for customers of large water sys- tems with only a few wells impacted by high As levels, to ap- proximately $100/month for customers of very small water sys- tems in which their only well requires treatment Bitner et al. 2001; Gurian et al. 2001. An alternative to centralized water treatment for As removal is point-of-use POU treatment systems. These are small units in- stalled at the customer’s tap. The advantage of POU systems is that they only treat water intended for human consumption or household use. POU systems are typically installed in the kitchen and provide a separate tap for the water used for drinking and food preparation. Examples of POU systems include home water softeners, under-the-sink water filters, and under-the-sink reverse osmosis systems. The objective of this study was to construct and test an under-the-sink POU system for As removal and to develop an estimate of the costs for its use in a small community. Background Previous investigations of As removal from groundwater have focused on four technologies Clifford and Lin 1991; Amy et al. 2000; Chwirka et al. 2000: membrane processes; ion exchange; activated alumina adsorption; and iron hydroxide coagulation and microfiltration. Centralized reverse osmosis is not suitable for small utilities because it is too expensive and complicated, and because it wastes too much water. Ion exchange and iron hydrox- ide coagulation/microfiltration are also problematic for small sys- tems; IX because it has a very large salt requirement and associ- ated brine disposal requirements, and iron hydroxide coagulation/ microfiltration because it is a complicated treatment process that small utilities cannot afford nor operate. Clifford and Lin 1991 investigated As treatment options for San Ysidro, New Mexico and concluded that POU systems based on under-the-sink reverse osmosis RO units would be most ef- fective for this small community. With financial assistance pro- vided by the Environmental Protection Agency EPA, RO sys- tems were installed in every residence and commercial establishment in the community. These systems are still in use and this community is believed to be the only one in the United States which relies upon POU systems for As treatment. Thomson et al. 1995, 2000 evaluated the performance of these systems and found that, while they provide a high degree of As removal when they are regularly maintained, regular maintenance is diffi- cult to achieve, thus the performance of the POU systems has 1 Professor, Dept. of Civil Engineering, Univ. of New Mexico, Albuquerque, NM 87131. E-mail: bthomson.unm.edu 2 Graduate Student, Water Resources Program, Univ. of New Mexico, Albuquerque, NM 87131. 3 Project Manager, CH2M Hill, 6001 Indian School Road NE, Suite 350, Albuquerque, NM. Note. Associate Editor: Wendell P. Ela. Discussion open until Novem- ber 1, 2003. Separate discussions must be submitted for individual pa- pers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this technical note was submitted for review and possible publication on August 7, 2001; approved on June 30, 2002. This technical note is part of the Journal of Environmental Engineering, Vol. 129, No. 6, June 1, 2003. ©ASCE, ISSN 0733-9372/2003/6-561–564/$18.00. TECHNICAL NOTES JOURNAL OF ENVIRONMENTAL ENGINEERING © ASCE / JUNE 2003 / 561