Dilution or concentration? Either way, we are damned
Published July 5th, 2018
Water efficiency and environmental protection seem increasingly at odds with one another. It is a problem that was highlighted for me this week by my colleague Charlie Walker’s presentation of trends in the water technology market for our WaterData webinar.
Big companies with consumer brands have been under pressure to reduce their water withdrawals. Transparency initiatives, such as the UN’s Global Reporting Initiative and CDP’s Water Program, have encouraged corporate water users to find ways of making do with less water. There has been a boom in high-recovery desalination technologies aimed at squeezing as much fresh water for reuse out of effluent streams. Other efficiency measures include cascading water uses within a facility so that process water is applied first to where the highest degree of purity is required, and modifying operations to be more water-efficient.
This makes a lot of sense, but it ignores one awkward fact: diluting and transporting waste is in itself an important use of water. Use less water, and your waste is bound to have a larger impact on the environment. For example, an industrial process might create an effluent stream with total dissolved solids of 200mg/l. That will probably meet the relevant discharge limits, but if you then decide to recycle your wastewater several times before discharging it, you might find the TDS rising above 1,000mg/l, and you will get fined for busting through the regulatory limit.
Non-biodegradable waste is an intractable problem. It doesn’t go away. Mostly we hide it in landfill or in deep wells or dilute it with water. It would all remain out of sight and out of mind if we didn’t at the same time start worrying about water conservation and looking after the oceans.
Charlie’s presentation showed that one of the hottest areas of new technology development is non-thermal brine concentration. It is hardly surprising. With fewer options to dilute waste in water, the best alternative is to minimise its volume through concentration, and send it to a disposal well.
In the longer term, I suspect that the solution will be two-fold. First, to reduce the volume of waste that needs to be hidden in water, and second, to find a way of recycling materials from wastewater to create new value streams.
Whatever the solution, I suspect that we will need to look to China to provide it. That country combines the world’s tightest industrial wastewater discharge standards with the greatest need to conserve water.