Where can I find information about Nitrate/Nitrite in water?

Nitrate

Nitrate (NO3) is a naturally occurring ion present in the environment and is a major nutrient essential to all life. It is a product of the oxidation of nitrogen by microorganisms in plants, soil, water and to some degree by electrical discharge (lightning). The nitrate ion is relatively stable. Therefore, most nitrogenous materials in the environment tend to be converted to nitrate.

Sources

Sources of nitrate in groundwater include decaying plant or animal material, agricultural fertilizers, manure, domestic sewage and geological formations. Higher nitrate concentrations are frequently found in shallow wells in rural communities with intense fertilization and farm crop production.
High nitrate is often the result of inadequate protection from surface drainage. Nitrate is readily dissolved in precipitation and is easily carried by rain and melt water through our permeable soil and overburden into groundwater supplies. Nitrate at high concentrations can be a health hazard.

Guidelines

The Guidelines for Canadian Drinking Water Quality 1989 has set the maximum acceptable concentration of nitrate in drinking water at 45 mg/L as nitrite (NO3) or 10 mg/Lwhen expressed as nitrate-nitrogen(NO3-N). This value is based on the relationship established between nitrate and the possible occurrence of infantile methaemoglobinaemia (also known as cyanosis or "blue baby disease"). This value was established to protect the most susceptible and sensitive subgroup of the population, infants less than three months of age. Also susceptible are women who are pregnant, and adults with methaemoglobin reductase.
In addition to methaemoglobinaemia, an association between the ingestion of nitrate/nitrite in drinking water and gastric cancer has been observed in some studies although the evidence is weak. Nitrate has not been found to be carcinogenic in chronic animal studies. Nitrate has therefore been included in Group IIIA (possibly carcinogenic to humans), however as noted above, the weight of evidence is weak.
Although the guideline is based principally on effects in the most sensitive subgroup (infants) of infantile methaemoglobinaemia, it is considered prudent to minimize the exposure of the entire population to nitrate owing to suggestive evidence of an association in several populations between gastric cancer and moderate levels of nitrate in drinking water. Therefore, the guideline is intended to apply to both children and adults.

Treatment

Treatment techniques for removing nitrate from drinking water include chemical reduction, biological denitrification, ion exchange, reverse osmosis and electro dialysis.
The treatment which has received the most attention is the ion exchange method. Domestic water softeners with an ion exchange resins are used to achieve concentrations well below the maximum acceptable concentration of 10.0 mg/L.
Reverse osmosis treatment has proven to be an effective method for nitrate removal but it is a relatively expensive process and may not be feasible.
In addition to water treatment, another method of nitrate removal from the drinking water would require the construction or reconstruction of a water well. This frequently involves the installation of additional casing beyond the length (depth) normally required by regulation.