(See endnote 22)
Nitrification is caused by microbes and is a process whereby reduced nitrogen compounds, usually ammonia, are oxidized to become nitrites and nitrates. Nitrification, which can degrade water quality, can reduce alkalinity, pH, dissolved oxygen, and chloramine residuals while helping bacteria grow. Ammonia can also be produced by this process. Nitrifying bacteria grow very slowly and typically nitrification usually occurs in large reservoirs and in areas of the distribution system where the water flows very slowly.
National Primary Drinking Water Regulations
National Primary Drinking Water Regulations or NPDWRs have been established for microorganisms, disinfectants, disinfectant byproducts, inorganic chemicals, organic chemicals, and radionuclides. These are legally enforceable standards for public water systems. They limit the amount of contaminants allowed in drinking water in each of the above categories. The MCLs are provided in a list of contaminants. (See endnote 25 for the most recent list of contaminants and their MCLs.)
Best Practices for Use of Disinfectants in Water Treatment Plants (See endnote 29)
- • To determine the best disinfectant to use for a site-specific water treatment plant, consider the following: determine the watershed that will be utilized for the raw water and any special risks created by different types of pollutants entering the watershed; predetermine by testing the amount and type of pathogens to be removed as well as the quantity, quality, types, and concentrations of raw water to be processed; determine the amount of contact time needed for proper disinfection; determine the efficiency of the disinfectant; determine the level of residual disinfectant which is needed in the distribution system; determine the costs of operating each of the potential disinfection systems; and determine the possibility of disinfectant byproducts which could be harmful to people.
- • Determine the efficiency of all parts of the water treatment plant process and how this affects the need for specific quantities of disinfecting materials and specific contact time.
- • Determine the effectiveness of the disinfecting process for bacteria, viruses, protozoa (Entamoeba histolytica, Cryptosporidium, Giardia) and helminths (parasitic worms).
- • Recognize that the diameter of the oocysts of Cryptosporidium are too small to be effectively removed by rapid sand filters and therefore there needs to be an additional filtration system, plus appropriate disinfection techniques, to prevent the disease process from occurring. High fecal contamination sources upstream of the water intake valves are a particular problem regarding Cryptosporidium. Natural flooding of these areas also is a serious problem. Where groundwater is used as the raw water source, flooding can also contaminate this source and create problems of potential outbreaks of disease. Other problems include inadequate treatment of the surface water, poor monitoring techniques, improper backwashing of filters, and bypassing the filtration system when the demand for water exceeds the supply available.
- • Utilize the physical removal and chemical oxidation of organic and inorganic compounds in the water to also reduce pathogenic organisms.
- • Limit the quantity of disinfection byproducts by controlling the residual organic and/or inorganic compounds in the treated water.
- • Test frequently during the course of each day to determine if the disinfectant residual is at its proper level in the water to be distributed and in the distribution system and also if there are organisms that could cause disease.
- • Consider the potential for health and safety issues among personnel when handling disinfectants which may cause serious concern if spills occur or excessive amounts are used.