Nutrient fluxes from domestic wastewater: a national-scale historical perspective for the UK 1800–2010

Nutrient emissions in human waste and wastewater effluent fluxes from domestic sources are quantified for the UK over the period 1800-2010 based on population data from UK Census returns. The most important drivers of change have been the introduction of the water closet (flush toilet) along with population growth, urbanisation, connection to sewer, improvements in wastewater treatment and use of phosphorus in detergents. In 1800, the population of the UK was about 12 million and estimated emissions in human waste were 37 kt N, 6.2 kt P and 205 kt organic C per year. This would have been recycled to land with little or no sewage going directly to rivers or coastal waters. By 1900, population had increased to 35.6 million and some 145 kt N were emitted in human waste but, with only the major urban areas connected to sewers, only about 19 kt N were discharged in sewage effluent. With the use of phosphorus in detergents, estimated phosphorus emissions peaked at around 63.5 kt P/year in the 1980s, with about 28 kt P/year being discharged in sewage effluent. By 2010, population had increased to 63 million with estimated emissions of 263 kt N, 43.6 kt P and 1460 kt organic C per year, and an estimated effluent flux of 104kt N, 14.8 kt P and 63 kt organic C. Despite improvements in wastewater treatment, current levels of nutrient fluxes in sewage effluent are substantially higher than those in the early 20th century.