When you flush the toilet, where does it go? The likely answer for most of us is that it goes into a network of pipes and pumps, mixing with wastewater from other buildings and rainwater runoff from roads, eventually making its way to a centralised Sewage Treatment Works. Here the waste is separated into solids and liquids, after removing sanitary products and skimming off the fat that is poured down kitchen sinks. The liquids often go through a series of treatment phases, such as rotating biological contactors, before being discharged into rivers or the sea. The quality of the treatment is monitored for a range of indicators of pollution (nutrients, bacteria, sediments and toxins), and the permitted effluent quality depends on the sensitivity of the receiving watercourse to pollution. Solids are dried out into sludge which is then in some cases applied to fields as fertiliser, or else destroyed.
The water we drink either comes from groundwater or from rivers. Both can be polluted, and are usually treated first. Depending on the source of the water, treatment may be a simple sand filter or a more comprehensive sanitisation by UV light, chlorine, or increasingly now fluorine because pathogens have developed greater resistance.
We live in a society which has enabled us to flush and forget; most of us give little thought to where the waste goes and what happens to it. However, there are some problems with the centralised approach to water services:
- The infrastructure is large scale and therefore costly. It is also old – in many parts of the country, engineers are not sure of the extent of the sewer pipe network, and existing pipes are near the end of their lifespan. The cost of replacing the current system, as well as expanding it to meet modern requirements, is massive.
- The centralised approach is energy intensive, because it relies on pumps and electrical treatment machines. The carbon footprint of the UK’s water services is therefore large.
- Ageing infrastructure is not fit for purpose. It often leaks or surcharges untreated waste into streams or up into homes. Frequent leaks of pollution into rivers and the sea occur across Britain, where there are some 20,000 legal but unmonitored sewer overflow points. Heavy rains burst sewage pipes because they take rainfall from drains.
- Water companies represent large-scale big business, returning large profits. Although they are supposed to re-invest this into the infrastructure, many people are still suffering the effects of pollution. It is a government enforced monopoly, which goes against principles of free-markets as dictated by the Water Act in 1989. The World Trade Organisation also stipulates the need for free markets. To the public, this means that there is no alternative to regional water companies for a basic and essential resource such as water. There is no competition to drive down prices and keep up quality. The costs to the customer are high and increasing in order to fund the large scale replacements of the current infrastructure.
- Multi-resistant strains of bacteria and viruses may be produced by concentrating sewage into centralised Sewage Treatment Works. The hostile environment and presence of antibiotics washed down drains promotes competition between pathogens and the transfer of genetic material.
- Where treated effluent is returned to watercourses, some studies have noted eutrophication, gender swapping in fish and amphibians due to hormones washed into the system, silt and other pollutants. Treatment is therefore not always effective.
- By diverting rainwater into the sewage system, we waste this “grey water” and instead use drinking water to wash cars and flush toilets. This exacerbates low flows in rivers and groundwater over-abstraction.
- Short-flush toilets designed to conserve water actually pose a problem for the sewage system, which relies on this water to flush the solid waste many kilometers down pipes to Sewage Treatment Works.
- The Transition town and Carbon neutral movements can make a real difference by setting up competitive waste water services. Local land owners and farmers may wish to work with Community Supported Utilities offering decentralised sewage treatment via reed beds and biomass plantations. In some areas where sewage pollution occurs frequently and there is a critical threat to public health this approach is urgently needed.
Rose George (2006) The Big Necessity: Adventures in the world of human waste.