Fact: Recycled sewage water could be cleaner than the water in your tap – here’s why

The truth of the matter is that correctly recycled wastewater is every bit as safe as other drinking water, and in some cases, even purer. As is so often the case, avoidable misconceptions form the base of a completely unnecessary bias. Education is, conceivably, the most powerful tool in the effort to open minds, and in this article we’d like to give you some water for thought.

UN-Habitat estimates that about 90 percent of the world’s wastewater is untreated and enters bodies of water in its raw form. This isn’t only detrimental to the environment and the health of communities; it’s a massive underutilisation of a scarce resource.

A variety of uses

Recycled wastewater (reclaimed wastewater) can be used to service a wide variety of applications – not just drinking/potable water. For example, it’s safe for:

  • Agricultural irrigation and the growth of animal feed;
  • Reuse in urban environments in the context of irrigation of green areas, parks, etc.;
  • Household reuse, especially garden irrigation and non-potable uses like flushing toilets;
  • Industrial processes, including power generation, cleaning and cooling towers;
  • The augmentation of water bodies in the natural environment, and;
  • Land improvement.

All of the above lessen the burden on valuable fresh water supplies, and as a consequence, make a major contribution to sustainability and water conservation.

Drinking water – Waste not, want not

Regarding drinking water, there are two methods: Indirect Potable Reuse and Direct Potable Reuse. Before looking at these, it’s probably best to first examine, in a very general and simplified manner, some of the processes through which wastewater can be cleaned and purified.

Namibia has been using recycled wastewater since the 1960s, and today, 25% of Windhoek’s water supply is reclaimed from wastewater treatment plants.

  • Pre-treatment – in this phase, water that enters the wastewater treatment plant is cleansed, by means of a mesh or bar screen, of large pollutants like cans, twigs, branches, plastic bags, rags, etc. Grit (e.g. sand and gravel) is also removed. One example of how this is achieved is by slowing the influent down in a grit chamber, thereby allowing the heavier particles to sink to the bottom.
  • Primary treatment – here, sedimentation takes place by allowing the “wastewater sludge” to settle at the bottom of a static water basin (a settling basin) while less dense substances like grease, oil and fat rise to the top of the basin. Both the sludge and the less dense materials are removed through mechanical processes.
  • Secondary treatment – in this stage, organic waste (like solid human and food waste) is removed through the action of naturally occurring micro-organisms. Bacteria and protozoa use the organic waste as a food source, and do a phenomenal job in further cleaning the water.
  • Tertiary treatment and purification – this stage includes a large number of possible processes, and if water that’s suitable for release into sensitive ecosystems or for drinking purposes is to be obtained, tertiary treatment and purification are needed. Tertiary treated water may also be used to recharge both surface and ground water. For purified water, disinfection must take place to render all pathogens inert, and all remaining toxins must also be removed. There are several methods to do this, but it suffices to say that these processes have been thoroughly researched and consistently produce high quality water.

By the time the reclaimed water reaches your tap it’s as safe to drink as your normal supply.

Back to Direct and Indirect Potable Reuse: Water that has been disinfected of pathogens and toxins in tertiary treatment is either pumped directly into a municipal potable water treatment plant (from which drinking water is distributed to reservoirs), or it is first pumped into surface or ground water that is then collected for treatment in the municipal plants. The first method is Direct Potable Reuse. The second method is Indirect Potable Reuse as freshwater/ground water bodies are used as buffers before the water is sent for further treatment. Both, so long as the correct processes have been implemented, are safe for human consumption.

Now, help spread the word…

The myths about the unsuitability of reclaiming wastewater abound in popular chit-chat. Armed with the correct information, however, we South Africans may overcome our fears and tap into a water resource that could be absolutely indispensable in years to come. And, hey, if you’re still in doubt, know that Namibia’s efforts have been successful for 50 years – and counting.

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