If the recommended minimum water use for LDC cities of c.36 lt./day/person as suggested in Figure 1 is disaggregated into its four main components, it is evident that flushing toilets is the largest single category of domestic water use and the only one with significant room for reduction. (The average OECD sanitation use is 40 lt./day and all other uses, except drinking, are comparably greater.) There is no room for conservation of drinking water; virtually none in cooking; some in the bathing category through, for example, water-conserving shower and faucet fixtures.³ Sanitation using flush toilets has, by contrast, substantial scope for water conservation; and sustainability demands that it be stringently reduced, preferably to zero. That water for flushing toilets can be reduced to zero has been demonstrated successfully by the use of composting toilets at public facilities and residences in the U.S., Sweden, and South Korea (to name a few countries where this technology has been seriously applied), where a household of four saves 40,000 gals./yr. and a public facility serving 70,000 people saves 350,000 gals./yr. Sweden’s entire province of Tanum is converting to composting toilets in order to reduce pollution of beaches and damage to fisheries, and because it is cheaper than conventional sewering according to Schnbeck (1996). Other provinces are following that lead. Tanum has found that their composting method reduces nitrogen and phosphorus pollution 90-95% below the levels reached by conventional sewage treatment plants.

3. DIVERSION OF SCARCE WATER TO SEWERAGE

Clean water, an increasingly scarce commodity, should be allocated to its most productive and sustainable uses. >From the point of view of the availability of water alone, most cities do not have enough fresh water to justify continuing with central collection sewage systems. Transportation of wastes by water requires huge amounts of water just to keep the wastes moving in the pipes. This has been demonstrated in a number of U.S. cities where many sewer lines plugged up after water conservation programs introduced the use of 1.6 gal. toilets instead of the usual 3-5 gal. flush. People with such low-water toilets must now flush twice or thrice.

The situation in many areas is so severe that some countries are having to seek alternative sources of water. In Hong Kong, sea water is now used for a parallel sanitation system. But, since building a parallel system of distribution for sea water would be too expensive for most older cities, brine may be pumped into existing fresh water systems. However, a likely danger of such a choice would be contamination of fresh groundwater supplies by exfiltration from leaking sewerage. This would further degrade groundwater -- the world's prime source of fresh water. Further, current infrastructure for transporting fresh groundwater to people for drinking, cooking, and washing would be rendered unusable. Fresh water would then have to be supplied by truck or containers -- clearly an expensive proposition.

4. WATER LEAKAGE

Maintenance of water supply and sewage collection infrastructure, even in affluent OECD cities, entails an increasingly onerous cost, since many municipal sewerage systems are in advanced states of decay. Sewage leakage into water supplies and into groundwater is increasingly common worldwide. Municipalities are uncertain where financing for rehabilitation of the pipes can be found. If the situation is desperate for OECD cities, the problem of funding the rehabilitation of leaky water supply and sewer systems is orders of magnitude worse for LDC cities, which by definition have less money to spend and where human populations are already larger and growing faster.

5. THE FAILURE OF CONVENTIONAL SEWERAGE

The enormous expense entailed in the treatment effort to extract clean water from sewage is a wasted cost, since this vast expenditure of public funds has not -- and can not -- provide environmentally sustainable sanitation. That is, it cannot solve the multiple problems caused by this form of water pollution. As a system, it cannot clean the water we have chosen to pollute without introducing more complex and environmentally unsustainable effects. The reason lies in the flawed concept of the separation technology itself: it is a virtual impossibility to clean water that has been used to transport human wastes. The inevitable products of this system are first more or less degraded water, and second more or less toxic sludge. The more advanced the treatment of the sewage (i.e., the more successful the separation of the pollutants from the water), the more sludge will be produced and the worse -- the more unpredictable and dangerous -- this sludge will be.

The problems associated with central collection and treatment of sewage -- pipe laying, leakage and loss of water from sewers, the costs and the failure of ever more elaborate forms of treatment, and finally, the creation of sludge -- these are all endemic to central collection and treatment. Each stage only leads in its turn to more unsolvable problems as the primary problem is merely moved from one place to another, and from one form to another. The result of this attempt to manage human and industrial waste streams is that the end product, sludge, is so replete with pathogens, organic and inorganic toxins, and a virtually unknowable range of chemicals, that it is classified as a hazardous material requiring strict regulation for transportation and disposal.

6. WHAT TO DO WITH SLUDGE?

Ocean disposal of sewage sludge -- sludge which had just been removed from water -- was, in coastal cities of the U.S., standard practice until 1992. Though clearly unsustainable, it was nevertheless only after strong public protest that the U.S. Congress passed a law in 1988 (to be effective in 1992) banning ocean dumping. But the alternatives are also unsustainable. Landfilling, long the convention in cities far from oceans, pollutes groundwater. Incineration, in addition to pumping toxic chemicals into the air, generates dioxins that can be lethal in only parts per billion.

Both landfilling and incineration were employed for a number of years until environmental objections intensified. To fill the vacuum caused by this opposition, US Environmental Protection Agency (EPA) adopted the idea of disposing of the sludge by spreading it -- as a "fertilizer" -- on agricultural land. Sludge’s four main categories of pollutants -- nutrients, pathogens, toxic organics and heavy metals -- behave differently and cannot be managed by a single kind of treatment. Land application was implemented in Sweden in the early 1980s with disastrous results, which the US EPA seems to be ignoring. Such a practice must lead to accumulation in living tissues of heavy metals and persistent organic chemicals: first, they accumulate in the soil, then in decomposer microbes and soil-conditioning invertebrates. Other life forms are damaged as thousands of non-biocompatible substances move up the food chain. The toxic effect on crops, as well as on the consumers of such crops, is buying risks for the future.

Despite creating such risks, governments and environmental protection agencies the world over are forcefully promoting land application of sludge -- because it is the cheapest form of disposal. It is misguided of regulators to try to persuade the world that sludge, though undisposable, is recyclable -- suitable for "beneficial reuse" -- as the phrase now goes. In a sustainable world, nothing can be “disposed of,” but this doesn’t mean that everything now in human use can be recycled. What cannot be recycled is not sustainable and should not be produced. Sludge is one such material.

7. SOLUTIONS

First, we must stop debasing intrinsically valuable resources such as clean water and human excreta by combining them with all other "wastes" that can be made to fit down the drain, where they result in the unusable and undisposable material, sludge. Governments must come to understand what solving the problems now caused by these "wastes" really means in terms of environmental sustainability. Pollution prevention, sewage reduction, separation at the source, and water conservation should be maximized. Only thorough source separation can make possible the creation of products -- out of "wastes" -- that are environmentally benign (e.g., organic products that are compatible with normal metabolic processes). Other materials that are not life-compatible, especially heavy metals, toxic chemicals, and toxic organic materials used in industrial processes, must be retained in closed-loops and reused within the industries from which they come. Industry must be held accountable for the appropriate management of its own by-products. This means industry must not be allowed to abdicate environmental accountability by using sewers as a cheap dump. It is society in the form of human beings and their communities who now pay the financial and health costs of subsidizing this cheap garbage disposal for industries.

By converting "waste" materials to usable products at the point of generation, both the economic and the environmental costs of central treatment can be avoided. Obliging industry to participate in source separation programs moves responsibility -- including the fiscal burden -- back to where it belongs. Human excreta and clean water can then indeed be reclaimed for further beneficial use.

8. POLICY SUGGESTIONS

Clearly in such a complex field there are no panaceas. There are, however, three general principles which would revolutionize the management of this global predicament which should be tailored to local conditions such as climate and geology. All are applicable in most cities, and implementing even one of them would greatly alleviate current unsustainable practices. All are preferable to conventional trends. This paper suggests they be evaluated in view of the unsustainability of conventional practices.

The three general principles are first, institute a policy of sewer avoidance (i.e., stay off or get off sewers). Second, promote low cost, on-site resource recycling technologies, such as composting toilets, that avoid polluting water and preclude wasting resources. Third, price water right.

8.1 Sewer Avoidance

Such a policy has two parts. First, in the thousands of cities, towns, and communities around the world now served by one kind of on-site sanitation system or another (e.g., pit latrines, cesspools, and septic fields), just don't sewer. Instead, use development funds to install on-site remediation technologies, of which there are a number already on the market superior to septic systems in their ability to accomplish pollution prevention or abatement. The advantages of such a program are great:
a) development of communities is not bound to the rigid grid of sewer lines;
b) pollution problems can be dealt with piecemeal -- where they really exist, and where they are worst first;
c) capital as well as maintenance costs are substantially lower for on-site systems than for central sewering and treatment;
d) most importantly, the problem of water pollution becomes solvable instead of merely transferable.

Second, in cities and towns that are already sewered, implement a back-off-the-sewer program. That is, begin the process of intercepting -- and recovering for recycling -- the resources (the constituents of so-called "waste") as close to the source as possible. This does not mean closing existing central treatment facilities now: rather, it means implementing a policy of mandates to fund the use of existing technologies that can accomplish separation, recovery, and recycling at source. The aim is gradually to reduce the range and quantity of random materials entering the sewage stream, in order gradually to decrease the burden on central treatment facilities and, thereby, the volume of sludge produced. This back-off-the-sewers program includes the following:
a) Do not extend sewer lines. Local pollution of groundwater is not, overall, more environmentally destructive than massive relocated pollution caused by central treatment outfalls of partially treated effluent and the dumping, burning, or land application of sewage sludge. Instead, funds now allocated for the extension of sewer lines should be saved for implementation of systematic source reduction, source separation, and resource recovery technologies.
b) Upgrade the level of treatment in those plants where immediate protection of the priority recipient body of water is deemed worth the environmental damage to be incurred by the increased production of toxic sludge.
c) Implement programs of industrial point-source separation, and enforce those that exist. Because adequate data concerning industrial processes are available, it is comparatively easy to apply specific source separation techniques to industrial wastes. It is also relatively easy for regulatory agencies to monitor and control industrial discharges.
d) Beginning at the peripheries of sewered communities whose central treatment facilities are already overloaded, install composting equipment designed to convert to humus -- on-site -- all human excreta. This would intercept most organic and nutrient "waste" materials at their source, thus avoiding the problems characteristic of all efforts to remove them afterwards.

8.2 On-site Separation and Resource Recovery Technologies

Many technologies exist and have been in use long enough to be well understood which represent definite improvements over either septic systems or pit latrines from the point of view of sustainability. The most advanced in this respect is the combination of composting toilet and separated greywater treatment. Besides making sewer- avoidance possible, this approach makes it possible for all the resources involved -- urine, feces, food scraps, washwater, and all the soaps and other "pollutants" in washwater, to remain in the nutrient cycles. The excreta is stabilized before removal from the composting unit and then recycled back, odorless and safe, to agriculture. The washwater is used for irrigation of trees, shrubs, and gardens around the dwelling, in which process it will be cleaned by topsoil and then replenishes ground water. In this nutrient-cycling configuration, today’s damaging path exemplified by sewage creation, central collection and treatment and the resultant production of sludge -- can be avoided altogether.

Such genuinely sustainable technologies should be systematically supported by education programs, as well as by development money for mass installation, both for remediation and for new construction.

8.3 Getting the Price of Water Right

Any steps toward according water its true value will necessarily tend to make the more sustainable technologies more attractive to governments and to industries which now misuse water simply because it is so cheap. The importance of such a policy shift is self-evident.

9. SUMMARY

Central sewerage can never be made sustainable. The random mixing of unknown materials is inherently unsustainable. Spending any resources -- money, time, energy, materials -- on the extension of central treatment, either of the sewer lines and hook-ups or higher levels of treatment, is a waste of those resources.

From the point of view of environmental sustainability, any on-site sanitation system is better than central collection and treatment. This is true even of traditional and conventional on-site systems such as pit latrines and septic systems which can -- and do --pollute. But it is precisely because they are on-site that their remediation and upgrade through replacement with non-polluting, resource- recovery technologies is feasible. And given that such remediation is technically possible to do now without any lowering of the quality of life, there is no legitimate reason why this course should not be systematically pursued. The technologies exist: the political will to make it happen must be mobilized.

References

Gleick, Peter, 1996. Human population and water, meeting basic needs in the 21st century. Oakland CA, Pacific Institute for Studies in Development (ms): 21 p.

Schnbeck, Anders, [c.1996; n.d.] The municipality of Tanum: environmental quality determines the future. Stockholm, Solutions, pp. 30-32.

Notes

¹ Ecologist, 4872 Old Dominion, Arlington VA 22207, USA.

² President, ReSource Institute for Low Entropy Systems

³ Even more water could be conserved by constraining lawn watering and automobile washing.