DUAL PURPOSE

It’s time SA invested more in greywater systems, particularly for new builds, but what is the safest way to go about this?

DUAL PURPOSE

They call it the Big Dry. For as long as anybody can remember, Australia has choked on a long, waterless drought, characterised by dust storms, bush fires and months without rain. Droughts have become such a feature of life Down Under that Queensland-born film director George Miller used the scorched landscape as the inspiration for his Hollywood blockbuster Mad Max: Fury Road. The film is set in a bone-dry dystopian future Australia, where those who control the water control the world.

‘Growing up in an isolated rural town, I was very aware of the cycle of droughts and floods,’ Miller told the Hollywood Reporter. ‘So it was a natural thing to put in the story.

Looking at the meteorological data, it’s hard to see Miller’s film as entirely science fiction. Australia’s Millennial Drought – as it’s also known – saw record-low rainfall, exacerbated by dry conditions triggered by El Niño. Major reservoirs shrunk to 25% of capacity. Rivers evaporated. Lakes turned acidic. Groundwater in parts of the country became unfit to drink. Farms bore the brunt of it. Some regions ceased food production entirely. In some parts of the country, Mad Max: Fury Road looked less like a sci-fi movie, and more like the lived reality.

Necessity, however, is the mother of invention: and invention is exactly what Australians did. Today, an estimated two-thirds of Australian homes use greywater systems, which take water from dishwashers, showers and washing machines, and recycle it for use in toilets and gardens.

This will all sound relatively familiar to home-owners in the Western Cape. SA’s recent drought – compounded by the City of Cape Town’s Day Zero scare (the threat of taps being turned off) – had households across the region looking for ways to reduce their water usage. A run on rainwater harvesting systems turned ‘JoJo’ into a household name, and many residents installed greywater systems, or simply started using buckets to catch their shower water.

Yet as South Africans were gathering rainwater, buying bottled water in bulk and catching the greywater from their loads of laundry, there was a strange irony at the heart of all their efforts. Unless you’d switched off the toilet tap, every time you flushed your loo you’d use potable water from the municipal pipes.

That irony is not lost on Kevin Winter, senior lecturer at the University of Cape Town’s department of environmental and geographical sciences. ‘South Africa is quite a unique country, in which reticulated water comes at a very high cost at potable levels, and yet we do everything with it,’ he says. ‘It’s quite bizarre. There can’t be very many countries that still allow that to happen.’

The challenge, however, is that greywater is – by its very nature – not pure, and not necessarily potable. Winter explains that Australia’s reticulation system became contaminated to an extent because of the water quality that was being passed through the home reticulation system. ‘People in Australia increasingly started to buy water from the bottle,’ he says. ‘And I’m told that many Australians still don’t trust the system, and continue to use bottled water.’

Israel, too, is a global leader in water solutions – especially in greywater/wastewater. In response to fears around water quality, Israel’s Ministry of Health published guidelines in 2008 regarding greywater recycling that would be permitted for watering public gardens and flushing toilets.

‘The main problem with re-using greywater is the danger to public health,’ Israel’s Ministry of Health said in a statement. ‘Greywater contains a high concentration of micro-organisms that might pose a risk to public health if they come into contact with the public. Such contact might take place due to failures in the treatment and reclamation systems, due to contact with water used for irrigation, due to the penetration of greywater into the drinking water systems (which might be caused by cross-connections between the different systems in a building), and so on.’

The Ministry of Health went on to state that greywater use requires the installation and operation of advanced treatment plants, while effectively monitoring their operation.

‘Therein lies the difficulty,’ says Winter, pointing to the potential health risks. ‘It’s still early days, and the technology and behaviour with respect to that water – in other words, managing the health risks – are still to be carefully thought through. You’ve got to bring both the social and technical aspects together here. I don’t think that’s been happening well enough in understanding how to use water that might be slightly contaminated.’

As anybody who’s collected greywater during restriction periods will tell you, there is greywater that’s reasonably re-useable (from, for example, your rainwater harvesting tank); and then you there is greywater that’s clearly not fit for human consumption (say, from your washing machine after a particularly dirty load of laundry). As Winter emphasises, greywater is difficult to quantify because of its make-up – particularly in terms of the pathogens and diseases that it may carry.

‘It doesn’t have an easy definition,’ he says. ‘You need to monitor that water, and of course nobody can afford to do that. So you are at risk unless you can put systems in place that can be readily serviced and maintained in order to reduce that risk.’

The solution, then, would have your household water supply running off two systems: one for fresh, potable reticulated water, and another for greywater. Linking the two would increase the risk of cross-contamination.

Yet that’s only true for existing structures. An opportunity exists where new builds can include these systems from the start – saving a large portion of the costs of retrofitting greywater systems to run alongside the building’s existing water supply.

Even that is not a perfect solution. Mike Muller, a visiting adjunct professor at Wits University’s School of Governance, warns that there would also be extra costs with new builds. ‘If pumping is required – which is almost inevitable in single-storey dwellings – the maintenance implications and costs could become problematic,’ he says.

‘In many situations, it is also not obvious that there would be a balance between the amount of greywater available and the amount required. Double plumbing would then be needed to make sure that toilets could be flushed if there was not enough handwashing. That increases health-related risks, which are always present as we try to keep wastewater and safe water safely apart.’

Muller presents another option. ‘One way to reuse greywater is to let it run down the drains to the municipal sewage works and reclaim it there. This is probably the most cost-effective approach and the one that will save the most water.’ But none of this can be achieved without capital investment.

Winter suggests that any roll-out of a treated greywater system might best be started in wealthier homes. ‘If you can prove that it can be done at a reasonably cost-effective level in homes that can afford this, then hopefully it can trickle down into poorer urban homes,’ he says, referring specifically to the City of Cape Town.

‘If we’re going to make any innovation occur in the city, we should be working with the high- and middle-income group, because that’s where the most water is being used anyway.’

Winter believes that Cape Town’s future lies in looking at new, fit-for-purpose supplies of water to close the loop on the urban water cycle. ‘It makes a huge amount of sense to be generating systems within new buildings – especially ones that are capable of treating water,’ he says.

‘It’s also a matter of making sure that there are larger reservoirs around the building – particularly water harvesters – that enable the greywater to be diluted. Sometimes that’s the best way to handle greywater in the long term.’

For now, water-stressed areas will continue to explore their options around greywater, categorising it under the broad umbrella of ‘alternative water’. That label doesn’t sit well with Win­­­ter. ‘I don’t use terms like “alternative water” or “waste water”. It’s just water at different qualities.’

That distinction is key to solving the ongoing water crisis. By changing the way we look at the resource, and by using the appropriate quality for the appropriate use, businesses and households take a significant step towards effective water management – and a step away from the current, inefficient system, where the water we pour out of our taps and into our food is the same water we use to flush the toilet.

‘Having the technology to achieve this is one thing,’ says Winter. ‘Managing and maintaining that technology is expensive, and requires discipline. If we’re going to do this correctly, we have to bring the social aspect and the technical aspect together. Sometimes we address the technology without addressing the social behaviour that goes with it, and then we lose sight of what needs to be done in terms of the effective management of the system.’

By Mark van Dijk
Images: Gallo/Getty Images, Jotham van Tonder/HMimages

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