Could vinegar clean dirty water?
The causes and effects of water contamination are well documented. We know of the harm that can be caused when waste from nearby factories leaks into groundwater. We know that this can lead to serious health problems and impact entire communities. But what if there was a way to reverse the effects of contaminated water by using simple organic materials? A team of scientists at the University of Leeds in the UK has found that vinegar may have the special touch to make chromium compounds in polluted water harmless. Today, most governments have laws and severe penalties in place to prevent the introduction of any substance into groundwater. Of course, this was not always the case, with industrial plants such as textile factories, smelters and tanneries leaking harmful waste into groundwater for many years. We now know that the legacy of this steady trickle of contaminants into our groundwater is still with us in the form of problems affecting the health and well-being of people, and devastating ecological consequences. The approach currently used in many countries to deal with groundwater contamination, caused by both past and present mistakes, is to remove the contaminant, treat it (if possible), and store it elsewhere; somewhat of a problem 'transfer'. The process is costly, both in terms of the energy and resources required, and it does not necessarily remove the threat of waste exposure to humans and the broader ecosystem (it may in fact increase this exposure in the short term). The team of Leeds scientists from both the School of Civil Engineering and the School of Earth and Environment have come up with two ideas in response to this problem: change the substance used to treat the harmful compounds as well as the method used. Their testing and subsequent findings have shown that by adding dilute acetic acid (vinegar) to the affected water (notably, on site) allows bacteria to grow which alter the makeup of the chromium compounds, rendering them risk-free. Environmental scientist Dr Ian Burke from the university explained that the industrial processes originally used caused these chemicals to become soluble, allowing for easy spills into the groundwater. 'Our treatment method reconverts the oxidised chromate to a non-soluble state, which means it can be left safely in the ground without risk to the environment. As it is no longer 'bio-available', it doesn't present any risk to the surrounding ecosystem.' The team's approach relies on the capacity of the disturbed ecosystem to restore itself. Although chromate chemicals have been successfully treated in situ in neutral pH conditions in the past, the emphasis of the Leeds study is on extremely alkaline conditions, such as the site focused on in their study. Situated in the north of England close to a river, the site is a cause for concern because groundwater emerging from the waste, which was deposited more than 100 years ago, is alkaline. This potentially toxic landform has remained largely untouched since it first appeared in the 19th century. 'Highly alkaline chromium-related contaminants were placed in inadequate landfill sites in the UK right up until production stopped in the 1970s - and in some countries production of large quantities of these chemicals still continues today,' said Dr Doug Stewart from the university's engineering school. 'The soluble and toxic by-products from this waste can spread into groundwater, and ultimately into local rivers, and therefore will remain a risk to the environment as long as they are untreated.' In accordance with environmental regulations, before the Leeds team can test on site, the method needed to be proven. 'From the results we have so far, I am certain that we can develop a viable treatment for former industrial sites where chromate compounds are a problem,' said Dr Stewart. 'Our next step is to further our understanding of the range of alkalinity over which our system can operate. As society becomes more environmentally-aware, new regulations demand that past mistakes are rectified and carbon footprints are reduced. By designing a clean-up method that promotes the growth of naturally occurring bacteria without introducing or engineering new bacteria, we are effectively hitting every environmental target possible.' The findings from the study are published in Ecological Engineering, the journal of ecosystem restoration.
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United Kingdom