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chapter 14 - Drinking Water treatment and Distribution

Other significant drinking water regulations adopted recently by USEPA include the following:

  • Long Term 1 (2002) and Long Term 2 (2006) Enhanced Surface Water Treatment Rule for improved protection of consumers from Cryptosporidiosis

  • The Stage 2 Disinfection Byproducts Rule (2006) for additional protection against carcinogenic effects of disinfection byproducts.

In some cases, the State of California has adopted MCLs in advance of the federal adoption of an MCL. For example, in 2007, CDPH adopted a perchlorate MCL of 6 ug/L. This MCL is based primarily on potential adverse effects on the thyroid. The USEPA has indicated that it does not intend to adopt an MCL for perchlorate; rather, it will leave this up to each state.

There are sometimes issues in achieving simultaneous compliance with two sets of regulations that have different goals. Thus, a water system trying to comply with one regulation may make a change in treatment that results in a violation with another regulation. Balancing the inactivation and removal of pathogens through disinfection with the production of disinfection byproducts (such as trihalomethanes and haloacetic acids) is a problem faced by virtually all water systems in California that treat surface water sources. The work of water agencies towards optimizing treatment to meet multiple regulatory requirements in the disinfection process is now better understood.

New Technology

New or innovative treatment technologies are often developed to address new or more stringent drinking water standards, to improve the efficiency of a contaminant removal, or simply to reduce either the treatment plant footprint, energy consumption or to reduce or eliminate waste streams from the treatment process. Innovative environmental technologies hold the promise of being more effective than traditional methods and able to address the far more complex environmental problems that we face today. Technologies increasingly used in California as a result of new regulations include:

  • Ultraviolet (UV) disinfection treatment to comply with disinfection byproducts under the Stage 2 Disinfection Byproducts Rule and requirements for the treatment of surface waters under the Long Term 2 Enhanced Surface Water Treatment Rule.

  • Arsenic removal technologies including adsorptive (disposable) media to allow small water system compliance with the reduced arsenic MCL.

  • Biological treatment in the form of fixed bed, fluidized bed and membrane bioreactors to treat for perchlorate, and now being demonstrated for nitrate and other contaminants.

As a result of both increases in demand and the relative scarcity of new water supplies, many water providers are now shifting toward the treatment of sources formerly considered unsuitable for domestic use. Treatment processes such as reverse osmosis are used to desalt brackish shallow groundwater for potable uses and are discussed in greater detail in the resource management strategy, Desalination. The relatively new

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