The purpose of this project is to continue to produce outstanding drinking water for the community and to continue to meet all federal and state drinking water regulations. The United States Environmental Protection Agency (EPA) has proposed Stage 2 Disinfection Byproduct regulations that amend some of the drinking water requirements to further restrict the byproducts in water that can be allowed from the necessary disinfection of water. The Board of Directors of the Rivanna Water and Sewer Authority (RWSA) initially decided in May 2011 to meet these new regulations consistently and on EPA’s mandated schedule by converting the secondary disinfectant for the Urban Water System from free chlorine to chloramines by October 2014, and by adding granular activated carbon (GAC) filtration facilities to the smaller Crozet Water Plant and Scottsville Water Plant by October 2015 and October 2016. The decision was influenced by a staff recommendation that took into account the opinion of the staffs at the Albemarle County Service Authority (ACSA) and City of Charlottesville (City) that the added benefits of more advanced options for the Urban System were not likely to be deemed politically as worth the additional cost. However, a group of citizens organized within the community in 2012, many arguing that GAC filtration for the Urban System was worth the added cost. After a Safe Water Symposium in June 2012 and a joint meeting of the “four boards” (Albemarle County Board of Supervisors, Albemarle County Service Authority Board of Directors, Charlottesville City Council, and RWSA Board of Directors), in July 2012, the RWSA Board voted to include GAC filtration for the Urban System and “take chloramines off the table”.
This narrative provides some background about what disinfection byproducts are and how the plan was developed to make the improvements that are now being proposed under this project.
By way of background, there are two types of disinfection processes for drinking water. Primary disinfection occurs within the water treatment facility to kill or inactivate harmful viruses, bacteria, and microbial matter that may be in the water when it is pumped from the environment (stream or reservoir) to the treatment plant. Secondary disinfection is a trace residual disinfectant that remains in the water to prevent re-infection as it moves through the RWSA transmission pipelines and City or the ACSA distribution pipelines on the way to service connections to the homes and businesses served. Several chemicals or processes that are approved by the Environmental Protection Agency (EPA) for primary disinfection (e.g., ozone, ultraviolet light) are not approved for secondary disinfection because those chemicals or processes do not maintain a long lasting residual suitable for distribution systems. EPA recognizes both free chlorine and chloramines as acceptable secondary disinfectants provided that the concentration of either disinfectant in drinking water does not exceed four milligrams per liter (or four parts per million). EPA and Virginia Department of Health (VDH) regulations require the continuous presence of a secondary disinfectant throughout water distribution systems.
RWSA is presently using free chlorine for both the primary and secondary disinfectant, and proposes to continue to use free chlorine as both the primary and secondary disinfectant. This is an important consideration as it is both necessary for compliance with EPA regulations and it is a key feature of a multi-barrier approach to ensuring the safety of water we supply as a wholesaler to the City and ACSA. The capital project presently under design would add granular activated carbon filtration to the existing treatment facilities at all RWSA water treatment plants, including the Urban Water System (all of the City and the surrounding urbanized areas of Albemarle County, including areas surrounding the North Fork Business Park, and the Glenmore County Club area), the community of Crozet, and the Town of Scottsville.
Regulations regarding the requirements for disinfection of drinking water, and the limits on the presence of the byproducts of disinfection that can be present in drinking water, are both set at the federal level in regulations issued by the EPA. In developing drinking water regulations, EPA performs extensive scientific research of health effects, including extensive risk analysis, as well as evaluating and determining acceptable water treatment practices, to assure their regulations both protect public health and can be achieved. All EPA draft regulations are subject to public comment periods before they are promulgated as well as subject to appellate judicial procedures after promulgation.
EPA initially developed regulations for disinfection byproducts in 1979, at a time when most water utilities were using free chlorine. EPA has modified the rules several times since 1979, consistently tightening the standards, and each time the rules were tightened, more water utilities found themselves unable to maintain compliance with byproduct regulations except by making capital improvements to their water treatment process. Most water utilities across the country that have made capital improvements to account for more stringent byproduct regulations have chosen to convert their secondary disinfectant to chloramines, which is known to produce less regulated disinfection byproducts than free chlorine, with the cost of water being among the significant factors considered in selecting chloramines.
Each time EPA has tightened the disinfection byproduct regulations, RWSA's goal has been to attempt to maintain continuous compliance as long as possible by optimizing the chemical use and performance of existing treatment facilities while retaining free chlorine for both primary and secondary disinfection. In so doing, RWSA has not made water plant capital improvements specific to stricter disinfection byproduct regulations even as many utilities across the country already have.
Development of the Local Plan to Address EPA Stage 2 Regulations
The most recent changes in disinfection byproduct regulations by EPA have been called the Stage 2 rules. RWSA retained Hazen and Sawyer, consulting engineer, to audit RWSA's present treatment practices and identify the extent to which changes would be needed to assure compliance with the Stage 2 regulations, with priority given to operating practices and other non-capital related changes. An extensive amount of data was collected. In the end, Hazen and Sawyer concluded that continuous compliance with the Stage 2 regulations could not be assured without capital construction upgrades to the treatment facilities. Hazen and Sawyer's conclusions are summarized in a technical report dated July 2011.
Multiple capital upgrade options were then considered, to include: (1) constructing and operating new granular activated carbon filtration facilities; (2) constructing and operating new magnetic ion exchange facilities; (3) constructing additional water storage and chemical storage and feed facilities to convert the secondary disinfectant to chloramines; (4) constructing and operating new membrane nanofiltration facilities; and (5) converting primary disinfection to the use of ultraviolet light.
Literature within the industry readily recognized magnetic ion exchange as a more expensive capital investment than conversion to chloramines, but Hazen and Sawyer and RWSA recognized there was little history in the industry, or published information, on the extent to which adding magnetic ion exchange on the front end of a water plant would reduce the cost of operating subsequent plant processes and the extent to which such reductions over time might offset the higher capital cost. To assure this alternative received fair consideration, RWSA co-sponsored a research study using a "pilot plant" at the South Fork Rivanna and Scottsville WTPs that resulted in the world wide publication of a research paper by the Water Research Foundation. The findings however, were that magnetic ion exchange will consistently meet the Stage 2 regulations, but the operating savings were still significantly insufficient, leaving the magnetic ion exchange process as a more expensive way to meet Stage 2.
Likewise, Hazen and Sawyer confirmed through evaluation that the granular activated carbon filtration option and the membrane filtration option will consistently meet Stage 2 requirements but either option if operated consistently for all water treated would be significantly more expensive for the Urban Water System. Hazen and Sawyer also determined that the use of ultraviolet light for primary disinfection was more costly yet would not avoid the need to convert secondary disinfection to chloramines, thereby offering little advantage compared to the present process with chloramine addition. A summary of the consultant's estimated capital costs and additional annual operation and maintenance costs for these alternatives are summarized in Table 1 below:
A series of workshops were held by RWSA and Hazen and Sawyer with the staffs at the City of Charlottesville and the ACSA to review the pros and cons of all alternatives. After constructive discussions among the staffs, the staffs of all three organizations believed at the time that the benefits of the more expensive alternatives did not outweigh their high costs, and those high costs would not likely be politically acceptable (at the time of these workshops, citizen groups mostly associated with opposition to the proposed new earthen Ragged Mountain Dam were lobbying for lower water costs and rates). These joint staff discussions formed the basis of the recommendation presented to the RWSA Board to authorize a capital project that would provide conversion to chloramines for the Urban Water System. At the time this recommendation was presented, RWSA was engaged in intense public discussions regarding the Ragged Mountain Dam, a new Water Demand Forecast, and the need for an expanded Rivanna Pump Station, and those issues dominated the open discussion by the public during RWSA Board meetings. No citizen spoke in opposition to chloramines and in May 2011 the RWSA Board authorized the design of a chloramines alternative.
In early 2012 public opposition to chloramines began to be expressed to the RWSA Board, with a number of local citizens taking the view that it was worth paying a higher cost for drinking water to have granular activated carbon filtration instead of a conversion to chloramines. Some of these citizens expressed opposing viewpoints to organizations such as federal and state agencies who present chloramines as a safe and acceptable alternative. RWSA sponsored a Safe Water Symposium on June 21, 2012 which allowed citizens to ask questions to a panel of eight individuals who provided a wide range of viewpoints and expertise. A joint meeting of the “four boards” with a public hearing followed on July 25, 2012, where approximately 50-60 citizens spoke, all in support of GAC filtration over chloramines. Following the public hearing all four boards, including the RWSA Board, voted unanimously to take chloramines “off the table” and advocate some form of GAC filtration for Stage 2 compliance.
We have heard a few local citizens appeal to elected officials that no action by RWSA was required to remain in compliance with EPA rules. To the contrary, following detailed technical studies by experts, it is very conclusive that additional measures are required. Our drinking water regulations come from the federal government through EPA and the federal law does not allow compliance or non-compliance with those regulations to be at the discretion of local officials. EPA can impose penalties of up to $25,000 per day of violation for failing or refusing to comply with disinfection byproduct regulations.
On July 25, 2012 the RWSA Board authorized a “desk-top” study by Hazen and Sawyer to develop a preliminary range of potential costs for a GAC system, including what has been called “Hybrid”, referring to the partial use of GAC filtration to produce drinking water that will consistently met Stage 2 regulations without all of the costs associated with complete GAC filtration of all treated water. A “Hybrid” system may mean providing some but not all of the GAC equipment needed for full water plant capacity, and would probably mean blending some water treated with GAC with other water treated through existing conventional facilities but not GAC. The idea of blending is to extend the useful life of GAC, since most of the operating cost for GAC is associated with regenerating or replacing the GAC at the end of its effective service life. While “Hybrid” can reduce the cost of water, the trade-off is that the water, although compliant with all EPAstandards and therefore safe, will produce more disinfection byproducts under the Hybrid alternative than water that is fully treated with GAC.
Every Tue, Thur, Sat at:
