This document provides a new perspective on the issue of wastewater treatment, water management and climate change.
The text within this page was first published in French on www.eautarcie.com : in April 2008
The original text has since been adapted and first published in English on this page at www.eautarcie.org : 2009-06-15
Last update : 2017-01-30
This title can surprise many. We are all used to accepting the dominant theory without question, a theory by which the efficient discharge of purified wastewater in a receiving milieu can only be beneficial for the environment.
Take a river that has been severely polluted by a city's sewage discharge. Placing a sanitation plant that discharges cleaner water in a watercourse seems the most appropriate solution. The river is thus « saved » and all is best in the best of worlds (polluted, and then « de-polluted »).
Obviously, this all depends on the initial objective. If you aim to make a river (a bit) cleaner, without considering other impacts, the conventional approach seems OK. The problem is that Nature and the Environment form a whole that goes way beyond a simple aquatic ecosystem. So great is the environmental impact of present-day human activity that its consequences must not be mistaken as being limited to the single aspect of a river's water quality.
With its limited objectives, conventional wastewater treatment disregards a whole series of effects, located upstream and downstream from actual treatment. With sustainable water management in mind, a holistic vision becomes self-evident, if we are to accomplish a more comprehensive analysis of sanitation techniques. We must therefore endeavour to minimize the environmental impacts of domestic water-related activities . In this new vision, it can easily be shown that present-day urban wastewater treatment no longer plays its part as a sustainable practice.
Why has the science of sanitary engineering entered a kind of cul-de-sac? The answer to the current situation lies in a combination of historical factors - social, psychological and mostly financial – coming with the rise of modern cities.
As a science, sanitary engineering stemmed from concerns on public safety before the advent of urban wastewater management. The implementation of wastewater conveyance networks was the first step on this road. In large cities, this step has almost always preceded the onset of flush toilets. This means that the first « sewers » mainly collected greywater (soapy water), and no black water (containing human dejecta). For the engineers of those days, considerations centred upon evacuating wastewater from homes, without necessarily discharging it in a watercourse where it could cause problems. They therefore built non-impervious sewers, whose main role was not to convey wastewater to rivers, but to disperse it into the ground. This environmentally-friendly and pragmatic approach was also less costly than implementing impervious sewers.
In the first half of the 20th century, black water was not generated, or very little. Most of the population used latrines located in the furthest corner of the garden (or « backyard » in North America). From those days comes the word « outhouse », also called a « backhouse ». The contents of those noxious latrines were regularly removed by market gardeners (or « truck farmers » in North America) for use as farmland fertilizer .
The situation altogether changed with the advent and generalized use of WC's. This has radically modified the composition of wastewater collected and conveyed in sewers. The resulting black water has engendered organic nitrogen and phosphorus. Presently, 98% of the nitrogen found in urban wastewater comes from our flush toilets. Consider that nitrogen is a key factor of pollution, and simultaneously a key element in the workings of the biosphere. Current practice aims to purify urban wastewater as efficiently as possible.
This change has had three consequences:
• The destruction of nitrogen-containing organic matter (our dejecta) and its irreparable removal from the biosphere's nitrogen cycle, for purposes of wastewater purification. This has resulted in a disruption of Nature's great cycles: nitrogen, carbon, phosphorus and water.
• The release of organic nitrogen and phosphorus, in the form of nitrates and phosphates, which appear in nature as pollution .
• The disruption of the soil moisture regime in those areas serviced by centralized (or « mains ») sewerage systems.
Initially, these consequences were completely overlooked by scientists and sanitary engineers. The first problems appeared with the rise of pollution in our rivers. With the advent of WC's and the expansion of urbanization, the volume of wastewater discharged into rivers has increased, with the consequences we now know.
In earlier days, scientists were less attentive to interactions in the biosphere. An immediate short-term solution like wastewater purification appeared totally reasonable. They did not in fact realize that this technique was only a symptomatic treatment, and that the long-term solution would consist in going to the root of the problem. In conventional sanitary engineering, the wastewater purification approach has led to basic paradigms that, over the years, have become true dogmas. These flawed paradigms are:
Eliminating pollution « at all cost » has become a major priority.
It is when you examine environmental impacts that the drawbacks of conventional sanitation unfold. In our analysis, we have picked out three fundamental mistakes in the conventional (and generally accepted) approach.
The 1st mistake is that of considering techniques that emphasize purification efficiency while practically overlooking all other aspects. By such a misdemeanour, we seem to have forgotten that wastewater purification is supposed to help protect the environment. To do this, you also need to consider a set of aspects that come under what I call environmental performance. The criteria for these include:
• The energy consumption required to power, operate and maintain the wastewater treatment plant and conveyance network and to manufacture eventual reactive agents for the treatment process;
• The noise and smell from the machinery and truck-transport needed to carry-off sewage sludge;
• The environmental impacts of eliminating sewage sludge;
• The amount of nitrogen discharged into the environment, from treated wastewater and sewage sludge (expressed as kg of mineralized nitrogen / year / IH);
• The quantity of surface-active agents (detergents) discharged into a receiving water body (expressed as grams / year / IH);
• The quantity of medicinal and drug residues (expected in treated wastewater) discharged into a receiving water body (expressed as grams / year / IH);
• The disruption caused by a sanitation system on an area's soil moisture regime and a receiving body of water;
• The biological value (as potential humus) of nitrogen-based organic matter contained in black water, which would otherwise be destroyed and mineralized by its « treatment ».
Some of these criteria are included in environmental impact studies. Yet, the last one, which represents the biological value of our excreta, is by far the most important, but is always disregarded. Even if you were to hypothesize the most improbable notion that a wastewater purification system does not pollute the environment in any way, the fact that human faecal biomass is withheld from the soil formation process (for humus) qualifies conventional sanitation as a non-sustainable environmental practice. We mustn't lose sight of the fact that faecal biomass is only one of the facets in the management of worldwide biomass, which is absolutely vital for human survival on this planet. When human (and animal) faeces are withheld from the cycle, an enormous quantity of plant-based cellulose biomass can no longer participate in the soil formation process. It is only by correctly combining the management of both these types of biomass, one nitrogen-rich, and the other carbon-rich, that lasting food production can be perpetuated into the post-oil era without compromising the equilibrium of the biosphere's great natural cycles.
This reasoning leads us to define the second mistake in the conventional approach.
We persist in disregarding the impact of conventional sanitation on Nature's great cycles: water, carbon, nitrogen and phosphorus.
Be reminded that urban wastewater collection also influences the water cycle. Water used by a city's inhabitants is taken up within the flux of the water cycle, to be eventually restored to the water cycle. Considering present-day domestic water consumption, the water quantity involved can be substantial. For large cities, the water uptake disrupts a region's soil moisture regime in varying degrees. Taking up water from a region's water reserves and sending it back to a river by way of the sewers sort of short-circuits the water cycle.
Black water releases 80 to 100 kg of organic matter per person annually. This matter contains about 5 kg of nitrogen (N)and about 1 kg of organic (metabolic) phosphorus (P). Conventional wastewater treatment actually involves the bio-oxidation of this organic matter. Its hydrocarbon component is transformed into water and carbon dioxide, while its organic nitrogen and phosphorus are transformed into nitrates and phosphates .
Technicians strive to remove the phosphorus that remains after wastewater treatment. They present this as « a significant step » in the art of wastewater purification. The phosphorus extracted as struvite (ammonium phosphate of magnesia) is only a small part of what enters a wastewater treatment plant. The struvite acts as a fertilizer. By increasing water’s ionic strength in the soil, it accelerates the natural « combustion » of soil’s humus. Technicians insist that that « worldwide phosphorus reserves (from mining) will be exhausted in a century or two, and we will no longer be able to feed humanity, so it is important to recover phosphorus from wastewater ». One wonders how, over millions of years , the biosphere has prospered without phosphorus from mining? The answer is simple: all animal- and plant-based biomass was returned into the soil. Today, this process is seriously disrupted by conventional sanitation.
Pollution by nitrates and phosphates is really only a minor drawback of wastewater purification, when compared with the massivedestruction of organic matter. To conceive black water as a waste to be eliminated is erroneous. In truth, organic matter from our kitchen residues and from human and animal dejecta represents a precious resource that is an integral part of Nature's great cycles. The biological value of organic matter that we destroy by way of wastewater purification is far greater than the benefits obtained from such treatment. On this issue, I formulated a Fundamental Law in the 1990's, as follows:
« All organic matter that is destroyed for purposes of wastewater purification or energy production is a factor contributing to water pollution and the disruption of the biosphere. It diminishes the production capacity of our ecosystems ».
Considering the biosphere's current state of deterioration, we cannot continue indulging in the destruction of our faecal biomass by way of wastewater purification . Such destruction also aggravates worldwide water problems.
On this matter, conventional sanitation supporters assert the following ill-founded claims, which reveal an altogether differing reality under close scrutiny:
1. « The water quantity that transits through homes is negligible when compared to the water fluxes in nature. Disruption of the soil moisture regime is therefore minimal ».
On the contrary, disruption is substantial with respect to a land region's scale, markedly in large cities and areas of high-density housing. City planners are starting to recognize this fact and now recommend reducing the extent of impervious paving. Stormwater basins are even set-up near highways to reduce the effects of runoff. The water uptake by a city's inhabitants is equivalent to a river's discharge. The solution must involve partial control of runoff as part of an ECOSAN approach, to which I would also adjoin whole-house rainwater harvesting. The sum capacity of a city's cisterns (when correctly sized) is equivalent to a colossal stormwater basin.
2. « Organic matter contained in human dejecta is a negligible quantity within the biosphere's environmental balance sheet ».
Again, this is untrue, for human biomass exceeds that of most animal species on Earth. The nitrogen contained in human dejecta (as precious organic compounds) is equivalent to over 40% of the nitrogen used in agriculture worldwide. With world population increase, this ratio will further increase. It is therefore unreasonable to destroy this organic matter on behalf of wastewater purification.
3. « Tertiary treatment prevents pollution by nitrates and phosphates ».
In reality, tertiary treatment, which is called upon to eliminate nitrogen (and phosphorus), really only operates on 10% of the nitrogen that enters a sanitation installation. Of the nitrogen stemming from a plant's secondary treatment stage, 90% is found in sewage sludge. The focus must therefore aim to weigh up the exact nitrogen balance involved in wastewater treatment.
We persist in disregarding the fact that sanitation techniques that discharge wastewater to the receiving environment have a greater environmental impact than the techniques themselves.
An example of this mistake is the continued ongoing discharge of wastewater into surface waters, instead of its infiltration into the soil or its conveyance to closed or low-flow wetland systems. Ultimately, the consequences are:
1. Continued deterioration of river water quality (in spite of wastewater treatment);
2. Inordinate increase in sanitation costs;
3. Disregard or shelving of simple, inexpensive and efficient sanitation techniques .
Aquatic ecosystems are highly sensitive to the slightest pollution. We mustn't overlook the soil's remarkable purifying capability, especially in the rhizosphere. This gives rise to ecological sanitation's third principle.
A further mistake – an offshoot from the above - lies in the fact that the conventional approach weighs up wastewater treatment's environmental impact with respect to the impact of discharging non-treated water into a river. This erroneous approach unjustly presents conventional sanitation in a better light. The situation is quite different when you contemplate not discharging any wastewater at all into the river, in line with the six principles of ecological sanitation.
Conventional treatment systems present other major drawbacks:
1. The limited holding time (a few hours) for wastewater in sanitation plants is insufficient to decompose the molecules stemming from detergents as well as medicinal residues found in human excreta. When discharged into a river, these organic compounds represent a serious threat to aquatic life, even in weak concentrations . Waters become increasingly problematical to treat and transform into drinking water.
2. During rain events, a considerable mass of water flows into sanitation plants. The pollutant load found in the treatment plant and in sewers is then washed away directly into the receiving water body. Doubling the sewerage network (separate sanitary sewers and storm drains) is a solution that involves added costs. As shall be seen in the chapter on TRAISELECT in an urban setting, doubling the sewerage network by other means, in respect of ecological sanitation imperatives, will be much more environmentally efficient.
3. Conventional treatment doesn't eliminate the bacterial load that comes with black water. Before black water discharge into a water body suitable for public bathing, such water must first be disinfected (fourth stage sanitation treatment). When you are familiar with medical bioelectronics, you understand that disinfection profoundly modifies a receiving water body's electrochemical and biological properties. By killing bacteria, we are creating a biological imbalance, but we are especially creating a noteworthy health risk for bathers.
Wastewater purification using plants (also commonly called phytoremediation) has an ecological footprint that is almost as bad as conventional sanitation: such « alternative » systems obey to the same misguided principles. They too destroy black water's organic matter, and their purification efficiency is comparable. When a purification system involves composting of relevant plants (if composting even occurs), an extra solar cycle is lost in the recovery of organic matter, with greater waste than what could otherwise be retrieved by direct composting of eco-toilet effluent . More precisely, the organic matter’s « animal » component is removed from the cycle. On the other hand, if no black water is produced, purification systems using plants are unnecessary, and even harmful. In dry or arid regions, plant evaporation of wastewater’s water content represents an inadmissible waste. The entirety of grey wastewater must be either infiltrated into the soil (to replenish the water table) or used for crop irrigation. Doing this without health and pollution risks is only possible in the absence of black water. When black water is mixed with greywater, the tragedy is absolute: wastage of water and biomass, their irremediable loss for agriculture, and pollution of our watercourses.
Knowing the inadequacies of conventional wastewater treatment, one can legitimately wonder why we persist in maintaining this approach at all cost while at the same time penalizing pollution-preventive techniques that go to the root of the problem. It is undeniable that independent researchers would have developed alternative water management techniques a long time ago. The problem lies in vested interests that aim to maintain techniques that generate greater profits.
Extensive industrial and financial sectors have developed around conventional sanitation postulates. With growing pollution problems, the inevitable « de-pollution » of our rivers has now mobilized extensive human and financial means. Thus, pollution-prevention techniques have been disregarded on behalf of wastewater collection and purification – a remedial technique. Yet generally speaking, prevention costs much less than corrective measures, but it also generates less profit.
For market reasons, wastewater collection and treatment have been extended outside urban centres, even in rural areas where such techniques are unjustified, both financially and environmentally.
In matters of sanitation, decision processes have been sidetracked from the democratic route. In fact, sanitation plant suppliers and providers are intimately linked to the decision processes that should normally come under the responsibility of elected officials. Public works and materials supply contracts are usually subjected to laws that rule out interference from suppliers. Yet, these laws have not and are still not respected when it comes to awarding contracts for the implementation of sewerage networks and sanitation plants. Experts who are directly or indirectly linked to such companies are on committees that determine sanitation policies. Sometimes, for appearances' sake, university experts are delegated on these committees because they have no ties to the business world: practically speaking, this makes no difference. Now and again, we skirt the problem by creating « public » water corporations, where all technical options embody those supported by the business suppliers/providers. One can even speculate on the involvement of elected officials and their business concerns with sanitation and water supply industries.
In the field of sanitary engineering, scientific research is financially dependent of big business. University research labs can no longer go without such financing. That is why research is inevitably in line with the direction imposed by financial backers.
We can perceive the vested interests that go against better judgement and uphold the continuance of conventional sanitation options:
1. Priorities go to centralized collective installations;
2. Alternative decentralized techniques and pollution-prevention techniques are systematically disregarded.
Even the world of environmentalists has played into the hands of those vested interests. From lack of a holistic perspective, they have adopted the multinationals' point of view, when in principle, they are usually opposed to industry lobbies. They are among the first to demand the implementation of sewers and centralized treatment.
Cleverly, to deflect attention from the true technical problems, phytopurification (or phytoremediation) using plants has been presented as the only viable alternative to conventional sanitation. No one has noticed that this type of wastewater treatment obeys to the same concerns as conventional wastewater treatment: purify as best can be done, without worrying about the consequences.
It is interesting to note the stand taken by « alterglobalists » on water policies. These well-intentioned people do not realize that discussions concerning…
1. Universal access to water;
2. Rejection of water as a commodity;
3. A world « Water Charter »
…are ineffective to resolve worldwide water problems. In fact, these discussions never focus on the basic problem: that worldwide water problems stem precisely from those techniques recommended and even imposed by sanitation engineers. It is significant to point out that in international conferences on water policies, everything is discussed except the essential. No one, up to now, has denounced the costly and environmentally harmful consequences of imposing centralized wastewater treatment and centralized water distribution, worldwide.
What is the solution for better management of water generally speaking, and of wastewater in particular?
When you acknowledge ecological sanitation's great principles, you come to discover an incredible possibility: with ridiculous financial means and human investment, humanity could totally resolve its water problems within 2 generations (50 years). The precondition is to abandon currently imposed techniques and replace these by other, simpler, cheaper, more reliable and efficient ones. Most of these « alternative » techniques are presently outlawed, or at best, marginalized.
Short of a better-suited term, EAUTARCIE'S version of ECOSAN (as opposed to the generic version of « ECOSAN » referred to by others) has become the bulwark behind which can be defined the basic guidelines for truly sustainable water management, worldwide
These guidelines are expressed in the next chapter concerning ecological sanitation's basic principles, or the new paradigms of sanitary engineering.
To continue your reading, go to the Six principles of ecological sanitation