This project’s objective was to evaluate the effectiveness of available technology to meet the revised arsenic Maximum Contaminant Level (MCL).
This project was being conducted to answer question #4.2.1. of the ORD Research Plan for Arsenic in Drinking Water: How effective are available technologies for meeting a lower arsenic MCL?
This project consisted of three sub-projects:
- Nine water treatment plants currently removing arsenic from their source water were monitored for long-term arsenic removal. The nine plants selected consisted of two conventional coagulation plants, one lime-softening plant, two iron/manganese removal plants, and two ion exchange and two activated alumina plants. Water samples were collected weekly or biweekly for one year, and analyzed for a variety of water quality parameters to determine arsenic removal performance and general system performance. This effort provided for several short-term follow-up studies on the existing plants to determine the cause of any unusual performance results and on short-term studies of several other treatment systems, including point-of-use/point-of-entry (POU/POE) systems.
- A laboratory study was conducted to evaluate the effectiveness of seven different oxidants to convert arsenic (III) to arsenic (V). Because arsenic (V) is more effectively removed from drinking water than arsenic (III), oxidation of arsenic (III) to arsenic (V) will be needed frequently in order to achieve the revised MCL. The seven oxidants evaluated were chlorine, chloramines, ozone, chlorine dioxide, UV radiation, potassium permanganate, and an oxidizing media.
- A field study was conducted at three locations to determine the conversion of arsenic (III) to arsenic (V) by storage and aeration methods. The goal of this field study was to determine whether these simple oxidation techniques, effective for radon removal and iron oxidation, are also effective for the conversion of arsenic (III) to arsenic (V).
Information collected from these studies supported the development of the proposed revised arsenic MCL including the selection of the Best Available Technologies. The information will also be used by water utility operators to make decisions about modifications to their current treatment systems or about the selection of new or add-on technology in order to meet the revised arsenic MCL.
All nine plant studies have been completed. Three draft reports have been written:
Both the arsenic (III) laboratory oxidation study and the field oxidation study have been completed:
Short-term special studies continue on iron removal processes, new adsorptive media processes, and POU/POE systems.
Date Research Started
Date of Last Update