Research

Is dirty water better than clean?

Published 7 November 2012

Dirty water could actually be better for maintaining the health of some freshwater ecosystems, according to researchers from the University of Brighton.

Many waters are perceived to be of poor quality because of high concentrations of 'suspended particulate matter' or SPM - 1mm diameter pieces of eroded soil and organic matter that are found naturally in freshwater streams, rivers and lakes, which can give the water a dirty or muddy appearance.

But researchers discovered that high-levels of SPM are essential for the health of some freshwater ecosystems, a finding that could lead to changes in the way water quality is managed to protect aquatic wildlife.

The research, led by the university's Dr Gary Bilotta and funded by the Engineering and Physical Research Council (EPSRC) and Aquaread Ltd, is aiming to improve the European water quality guidelines for SPM, which were established to minimize and control SPM pollution caused by human activities such as mining, quarrying, agriculture, urbanisation and wastewater discharge.

SPM represent one of the most common causes of water quality impairment globally, and water containing excessive levels of SPM has to be rigorously treated before it is drinkable, increasing water treatment costs by up to 20 per cent and requiring more chemicals and carbon to clean it. At certain concentrations, SPM can also harm fish and other aquatic wildlife.

According to existing water quality guideline for SPM in Europe, concentrations should not exceed 25 mg per litre.

The researchers studied 638 healthy stream and river sites in the UK, representing 42 different freshwater ecosystem types. SPM levels varied significantly among these different ecosystem types, for instance, in one type which is home to the Atlantic salmon, the SPM levels were 15 times lower than the current EU guideline, but in another ecosystem type the SPM levels exceeded the guideline level, despite being in a healthy state.

The researchers believe that this study shows that specific quality guidelines are needed for different ecosystems because in some ecosystems the SPM provides organisms with a food source and the habitat that the organisms need to live and breed in, whilst in other ecosystems SPM can harm organisms, even when at relatively low concentrations.

The research, which is published in the international journal Water Research, is already attracting attention from European policymakers. It has big implications for those involved in managing land use and water quality across Europe because under EU legislation land owners and water users who are perceived to be contributing to the failure of a waterbody to meet water quality guidelines, may face fines and have to contribute to clean-up costs.

The researchers are now developing a tool for setting ecosystem-specific water quality guidelines.

Find out more: Developing environment-specific water quality guidelines for suspended particulate matter, Water Research Volume 46 Issue 7 May 2012