Household appliances are getting more and more efficient at conserving water, and advertising claims that this helps conserve the environment.

Some time ago, I've seen a documentary about a German waste water treatment plant where the incoming water was slightly chlorinated and irradiated with UV lights to kill off bacteria, and fresh water subsequently added.

A spokesperson from the processing plant explained that these two steps have been added recently, as the public's conservation efforts have led to a reduced flow rate in the waste water system, allowing undesired bacteria to replicate more, and to an increased concentration of detergents, to the point where the bacteria used in the cleanup process would no longer be able to function.

This suggests to me that in a closed cycle, it would be better to "use" more water in order to keep the system within the flow rate it was designed for, rather than add the additional fresh water at the end of the cycle.

Is that correct?

  • This is a confusing title and an off-topic question. You're not actually disputing any benefits of reduced water consumption (reduced energy consumption etc). You're looking at a side-effect, the (solved) problem of concentrated pollutants in waste water, and claiming that the side effect outweighs the benefits. Since you're the only one making that claim, it's not a notable claim Jun 3, 2014 at 9:31
  • Also, FWIW, your idea is nonsense. The plant is treating concentrated waste water with chlorination, UV irradiation and dilution. You're suggesting instead they prepare much more drinking-quality water, water which they will also have to source, chlorinate and UV irradiate, then pump it all the way around the domestic water network, using much more energy for the same net effect. Jun 3, 2014 at 10:04
  • Adding the additional fresh water at the plant could ensure that just the strictly needed amount would be added and thus no water wasted. Also, pumping water through pipes (including your kitchen tap) consumes energy. It would probably consume less energy if the water is added only at the plant (e.g. from a nearby river) than at every household. Also, future improvements in processing plant technology could probably adapt to the lower inflow volume and could be optimized to clean less but more heavily soiled water more efficiently?
    – Scrontch
    Jun 3, 2014 at 10:05
  • According to the FAQ, Skeptics.SE is for researching the evidence behind the claims you hear or read. This question appears to be your own speculation, and is off-topic. Please edit it to reference a claim that other people are making and flag for moderator attention to re-open (or get 5 re-open votes).
    – Oddthinking
    Jun 3, 2014 at 10:22
  • This would probably be a better fit at sustainability.stackexchange.com .
    – PJTraill
    Aug 22, 2022 at 9:57


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