LETTERS...

Annelies Balkema, The Netherlands: Recycling wastewater – all things considered?

Closing water cycles

In a survey on public attitudes towards water recycling held by the University of Cranfield, respondents expressed a preference to reuse their ‘own’ water. It probably gives people a feeling of safety to know where the water comes from. However, if one fully trusts treatment it should not really matter where the water comes from. But can we fully trust treatment? Is it possible to treat water fully or should we always incorporate the safety of long retention time in long natural cycles before reusing the water?

Andreas Schönborn argues that, if one believes in the information transfer the way it is described in homeopathic theory, this means we should avoid ‘too close cycles’ with respect to wastewater recycling. However, if one believes in the ultimate dilution of homeopathy, it would not be wise to discharge diluted information to surface waters either. In urine therapy people even try to close the cycle on human level, based on the idea that the information about disfunctioning is in this way returned to the body. Of course these are extremes.

The interesting question is what length of cycle is safe for wastewater reuse? Everyone will agree that pathogens are a major risk, and that there are other risks as well. For instance traces of medicines and chemicals present in the wastewater that may act as endocrine disruptors, influencing the behaviour and fertility of species. One of the difficulties in the research on these endocrine disruptors is that the concentrations are near to the detection limits. It makes one realise that it is impossible to measure and treat everything.

It is obviously very difficult to indicate the risk of water recycling with respect to low concentrations of different chemicals. But this also accounts for the risks we face when these chemicals accumulate in ecosystems. Recycling is of course a natural event, in natural ecosystems, the flow of nutrients for instance is conserved as much as possible and input and loss are usually small compared with the volume, which circulates within the system, notably in terrestrial systems. It seems to be a sustainable direction to try and approach this for cities and their hinterlands.

I do not foresee a scientific revolution the way Andreas Schönborn sees it. I do see a wide variety of options for more sustainable urban water system, including source control, the use of different water qualities, separate treatment of different wastewater streams, and recycling of treated wastewater.

There are a lot of options with which we can design tailor made urban water systems incorporating the local available resources and preferences. When we are able to limit the amount and number of chemicals used, these systems can be low risk with respect to pathogens and other ‘problems’ contained in the wastewater.

For wastewater treatment and recycling it makes sense to keep different wastewater streams separate. In this way streams with higher risks such as blackwater (= wastewater from the toilet) can be treated differently and may be exposed to longer cycles than lightly polluted greywater (= lightly polluted domestic wastewater).

As water is used for many purposes, it is not so difficult to avoid too close cycles. Water used for dinking, cooking, and personal hygiene needs to be safe, but the amount is relative limited. While relative large amounts of water are used for instance for irrigation, which can be done with a lesser water quality.

I think it is good to realise that we need smart solutions that anticipate on new, even unknown, developments. This can only be done through continuously improving systems towards safety margins. These safety margins can be defined by sustainability, a balance of safety and costs in economic, environmental, and social-cultural sense. We do not need ‘too close cycles’, after all we are not living on a space-ship, but on earth in the caring capacity of a large ecosystem.

I strongly disagree with Andreas' statement that feeding slaughterhouse waste proteins to cows can be in some way ecologically sound - it is in no way sound to feed meat to a vegetarian - I could, but I will not, fill this entire newsletter with a reaction to this statement.

Annelies Balkema

Andreas Schönborn: Rejoinder

Dear Annelies,

Thank you for responding. To make it clear at the very beginning: The issue of "information transfer by water" is highly speculative and there is no proof today that it really exists. All I was trying to say was: There are hints here and there, that it may exist (and the existence of homeopathy and Baumgartner's work are two of them).

In case this phenomenon existed, it would probably be of importance to the risk assessment of wastewater technology in the future, and particularly of any technology advocating a "shortcycling" of human nutrients. I think, we should be aware of this possibility, to avoid being caught off guard if it should prove true.

Other than that, we perfectly agree on most of the issues, except for one: I never said or thought that feeding slaugtherhouse waste to cows is an ecologically sound practice. However, there is a parallel to the issue of "information transfer by water": Slaughterhouse wastes were fed to cows in spite of warnings by some people, that this might prove to be disastrous. However, before the disaster was there, hardly anybody listened to these warnings.

Were the responsible persons not aware of this risk? Did they value their short term economic benefit greater than any risk they perceived? Or did they even have their house ecologist pointing at nutrient and energy balances and saying how beneficial this practice was? I don't know, but having witnessed a lot of opportunistic argueing in the past, on various occasions, I wouldn't completely rule out that possibility.

I will continue to search for evidence about the "information transfer by water" issue and will do my best to report to our readers about the results in the future.

Andreas Schönborn, Editor