The water industry and the nitrogen cycle

Abstract

Owing to a rising trend of nitrate concentrations in many rivers and groundwaters that are used for water supply and at the same time the introduction of legislation that tightens limits, the water industry's attention has been focused particularly on this component of the nitrogen cycle. In some rivers in eastern England that are used for potable water supply, nitrate concentrations have, after extreme meteorological conditions, exceeded 100 mg l$^{-1}$ for short periods and, as a consequence, supply abstractions have at times been curtailed. The nitrate concentration in at least 100 groundwater sources in the United Kingdom exceeds 50 mg l$^{-1}$ either continuously or intermittently, and several of the wells most severely affected have been withdrawn from service and replaced by other sources. Over the last few years the water industry has mounted a substantial programme of investigations directed towards: (a) identifying the source of nitrate and the reasons for the rising trends in surface and groundwater; (b) predicting the rate at which nitrate concentrations will rise in future and the eventual levels; (c) controlling the problem by blending of supplies, treatment to remove nitrate, storage, and other methods, and the cost of such options.