SESSION-2 Watershed Hydrology / Pollution
PAPER-2 Some Thoughts on the Upgradation and Maintenance of Water Bodies in Urban Settings- Balasubrahmanyam S.N.

The history and the sad fate of reservoirs meant to store rainwater for use during the dry season in the Deccan, where rainfall is seasonal and often ill-distributed, are briefly given. The dangers attendant on not stemming abuse of inexpensively created, ancient storage facilities or not doing anything about setting down practicable wastewater emission standards and strongly enforcing them are highlighted.

The deleterious effects of discharge of raw sewage and industrial effluents in coastal areas, documented recently by the United Nation Environment Programme, are equally applicable to inland waters. The benefits of harnessing the not-too-expensive methods of natural purification of wastewater cannot be neglected.

An investigation of microbial activity conducted about half a century ago by Natarajan and Pillai, disclosed that turbulence in a channel with adequate gradient facilitates the dissolution of oxygen. When oxygen concentration reaches about 3.5 ppm, fluffy masses of ciliate protozoa ( Carchesiunm, Epistylis ) develop, flocculate suspended matter and microbial entities, including pathogenic ones. Since amino acids are also rapidly destroyed in the clarified sewage, the factors leading to development of high biological oxygen demand is removed.

This paper discusses how this finding can be adopted for rapid and inexpensive purification of sewage.

In a letter to the editor recently published in a prominent newspaper, a well-known writer on environmental matters thanks God for endowing a bevy of beautiful lakes in and around Bangalore. God would indeed be embarrassed to take what He would certainly think undeserved credit. For, He intended that there couldn't be any natural lakes in old geological formations – ‘new' mountainous regions like the Alps, the Andes or the Himalayas or fractures like Lake Baikal caused by tectonic movements yes, Deccan Plateau, no. He would rather accept thanks for positioning a civilisation in the Plateau that produced visionaries and engineers who created those lakes over the last thousand years or two.

Water bodies, created as collection points of run-off in the Deccan have served from time immemorial. The ancient visionaries knew the difficulties of carrying on productive agriculture in a tropical setting, with the seasonal rains confined to only a few months in the year. Those visionaries and engineers understood the lay of the rugged land and constructed earthen bunds strengthened by stone revetments at broad depressions characteristic of the Deccan. They installed gates for the controlled release of water for agriculture and for use by the villagers living nearby - indeed the 'keres' were often named after the villages. It is noteworthy that structures built to protect the head works were often decorated with stone carvings that have come to retain much architectural interest. The ministers of the king, the 'pallegars' and other local chieftains (Kempegowda) considered it an act of great merit to contribute money to construct those bunds (not dams, really). The potential beneficiaries supplied labour during construction. Members of a local respected family were appointed as guardians to look after the maintenance of the ‘tanks.' Little chapels were created on the bunds and worship offered to the protective deities..…… I could go on thus. But I shall stop here to ask God why He thought it fit to endow all those descendents of the original constructive people, who now inhabit the Plateau, with only with low mental capacity (I avoid using the more appropriate term ‘dimwits' here) that fails to understand that these water storages are, virtually, living systems.

Let me begin with what should be obvious even to the casual observer. Artificially created water bodies designed to collect ('harvest' is the current buzzverb) rainwater, commonly called 'tanks' in these parts, are being allowed to die in many ways. Because of urban 'development' on the foreshores, runoff diverted into storm water drains has reduced the amount of water that can be collected from rainfall. Denudation that accompanies urban development allows silt and debris to be carried into the 'tanks', reducing their capacity. In most cases, raw sewage is actively diverted into the storages (tanks) as part of so-called 'urban planning' because it can be done cheaply for the lazy reason that the 'tanks' occupy, of necessity, low areas. Dumping waste materials into the depressions not merely by irresponsible citizens but even by municipal street-cleaning staff compounds the matter. Within a short time the 'tank' ceases to exist. Land sharks, in connivance with corrupt authorities, soon claim the area.

A tourist from Sydney, Australia, who stayed in Bangalore for some weeks some years ago wrote a letter to the editor of a prominent newspaper that he had read about Karnataka's laudable concern over air pollution, particularly in Bangalore but had seen nothing about any attempts to control water pollution. He noted that a stream flows parallel to Mysore Road before bending away to the south through farmland. "It is a foul, black, stinking stream which, piles up drifts of dirty foam. No doubt it is fed by drains and sewers and also by industrial wastes. In the crowded buses on Mysore Road you can tell your whereabouts by its stench. Whatever industrial chemicals and other effluents it carries are certainly finding their way into the water table and the sources of washing and drinking water for the communities around. What would studies of the health of people over the next few years in such communities as Rajarajeswari nagar show? When I asked what grand plan was under way to control water pollution and industrial effluents in general, and to clean up this stream in particular, I am told there is no plan at all!"

Some ten years after that letter was written, a sewage treatment plant was erected, with foreign collaboration at great cost, over that particular stream (Vrishabhavati). I believe that plant is functioning even now though the stench appears not to have abated near the entrance to the Bangalore University.

There appeared not too long ago a report on a document prepared by the United Nation Environment Programme (UNEP) on the global threat from untreated sewage discharges to coastal people and the environment. The gist of the report was that inhabitants of southern Asia face a greater threat than anywhere else in the world from the discharge of untreated sewage, apart from endangering marine wildlife and habitats, and fisheries. The document was published as a follow-up to the World Summit on Sustainable Development (WSSD, Johannesburg). Almost 40% of the world's population lives within 60 kilometres of the coast in southern Asia, putting it at high risk of sewage-related diseases and even death.

Since the report made no mention of a tentative finding that discharge of raw sewage into the Caribbean from the southern U.S. and eastern Mexican coasts had endangered coral formations in the Middle Atlantic I thought, at first, that it was of the same ilk as a paper published by American authors in a respectable scientific journal holding India and China responsible for the largest emission of the greenhouse gas, methane, because domestic ruminants are kept in large numbers in those yet-to-develop countries. But then I had to take it seriously because it added: "There has been impressive progress in providing sanitation in many of the worst-affected areas …… But the population grew by 222 million, wiping out the gains that had been made." It continued: "One way of tackling this is to get key parties to set realistic but ambitious wastewater emission targets (WETs), echoing those that have been developed in many parts of the world for emissions of toxic chemicals and noxious gases from power stations and factories. In some cases, wastewater treatment systems modeled on those in Europe and the US may be needed. But there are many low-cost techniques that could make huge improvements ." The report did reflect current thinking just as set out in the brochure calling for papers prepared by the organisers of this Symposium.

In making recommendations, UNEP said the low-cost techniques could give the environment a double benefit. It added, in a rather obvious manner, that such techniques could include dry sanitation and natural sewage filtering systems like ponds, reed beds and mangrove swamps, and re-using and refilling groundwater reservoirs. It warned that many such natural systems, important habitats for wildlife such as birds and fish, are being cleared and drained for agriculture and other activities. "If more people are aware of their potential as 'natural' wastewater treatment systems, then more will be conserved for their economic and health benefits, as well as for their importance for nature and wildlife." There are some expert cost estimates of providing safe drinking water and proper sanitation to everyone in the world by 2025: $180bn a year, two to three times more than present investments in the water sector. That may sound very high but the benefits in terms of disease reduction and dramatic environmental improvements are also high."

Thankfully, there is a realisation on the part of persons, activists, organisations, etc. on the need to preserve and maintain clean water bodies in and near urban settings. But those who want to set things right   seem to entertain many misconceptions about how to go about matters (municipal bodies or even government agencies included!). Letting in untreated sewage is an unacceptable practice. But stopping sewage flow is not the remedy - letting in properly treated, cleaned-up sewage is. Indeed that practice is necessary since, as already said, the water bodies are virtual living systems - they need replenishment of water loss. Mere dredging and deepening, touted as "rejuvenation of lakes," for which large funding has recently been made available to a government agency, while necessary, is not a remedy that is going to pull the water bodies from the brink of death. Growth of water hyacinth is itself thought of as 'pollution'. It is a symbol of pollution, actually. It shows there is a lot of nutrient available in the form of unclean discharges into the lake.

Half a century ago, Dr. C. V. Natarajan, then Deputy Director in the Department of Public Health of Karnataka, noticed clothes being washed by washermen ( dhobies , agasaru ) in the traditional manner without any ill effects in streams he knew carried sewage from Bangalore. A preliminary analysis at the Public Health Institute (Seshadri Road, Bangalore) showed that the water was free from pathogenic organisms at and beyond the point where the washermen were active. He persuaded Professor S. C. Pillai of the Department of Biochemistry, Indian Institute of Science, to study and pinpoint the factor or factors that seem to lead to the upgradation of flowing sewage to apparent river-quality water. The collaborative work of Natarajan and Pillai lead to the publication of a series of scientific papers. The one that appeared in the Current Science ["Natural Purification of Flowing Sewage" by S. C. Pillai, G. J. Mohanrao, A. V. S. Prabhakara Rao, C. A. Sastry, P. V. R. Subrahmanyam and C. V. Natarajan, Current Science, XXIX (12), 461 (1960)] can be regarded as a summarisation of results then in hand.

The authors found that flowing sewage can be divided broadly into four zones the lengths of each of which depended (rather critically) on the gradient of the channel through which it was directed to flow:

First zone: Preliminary changes leading to clarification and oxygenation.

Second zone: Growth of protozoa leading to further clarification and oxygenation

Third zone: Nitrification

Fourth zone: The purified effluent is used for washing purposes.

Bacteria, as generally found in domestic sewage, and occasionally Salmonella typhi, Vibrio cholerae , were found in the first zone . Fungi of the Sphærotilus sp. were often present in samples. While algae were generally not seen, protozoa ( Rhizopoda - Amoeba and Arcella sp.; Mastigophora - Bicosoeca and Euglena sp.; Ciliophora - Colpoda, Colpidium, Coleps, Stylonychia, Paramecium, Vorticella and occasionally species of Opercularia, Epistylis and Carchesium ) were beginning to be detected. Besides, insect larvae ( Aulophorus sp.; Mosquito ( Culex sp.); Bloodworm - Chironomus sp.) were seen often.

The most interesting finding was that protozoa of species Epistylis and Carchesium developed in strikingly large numbers in the second zone. They formed large masses adhering to the rock or masonry surfaces of the channels. Insect larvae, now present in greater numbers, included Anopheles and rotifera. Snails fish (the mosquito larvae eating Gambusia affinis ) and frogs also made their appearance. Algae ( Oscillatoria, Ulothrix, Urospora Stigeoclonium, Pinnularia ) began to predominate in the third zone. Larger fish, frogs and water hyacinth began to proliferate. The water became less odoriferous.

I have recounted in much detail some of the results reported in the Natarajan - Pillai paper in order   to illustrate how the proliferation of different species in the successive stages of flowing sewage dramatically upgrades the quality of water. The work did not, evidently, look for the presence and concentration of heavy metals (e.g. chromium from tanneries, lead from battery works, cadmium from electroplating industries, etc.) that might prove lethal to the organisms (protozoa) whose presence leads to the upgradation.

Permit me now to quote verbatim from the paper the portion relevant to the authors' successful reproduction of the clarification/purification process under laboratory conditions using the protozoan species taken from the sewage channels where the second stage conditions prevailed: "……. the more important factors influencing purification of the flowing sewage include: (1) adequate agitation or turbulence of the sewage and other conditions in the channel, which facilitate the dissolution of oxygen to the extent of about 3.5 ppm.; (2) the consequent development in large numbers of ciliate protozoa notably of the species of C archesiunm and Epistylis which are always found in activated sludge. When these protozoan colonies were taken out, washed and introduced into the sewage (at 10-25% level, by volume) and the mixture gently shaken or into which air was bubbled for 1½ - 6 hours (depending on the number of the organisms), it was observed that the sewage was clarified and oxygenated almost to the same extent as under the natural conditions in the channels. The flocculating activity of the protozoa and the clarification of the sewage also seemed to explain the relatively high nitrogen content of the soils under the flowing sewage in the zone of clarification and to bring about nitrification and other changes, e.g. , rapid; removal of amino acids from the sewage in the succeeding stages of purification in the channels. The quality of the final effluents from these channels was similar to that from the activated sludge process."

The authors concluded their paper saying: "Natural purification of flowing sewage is thus essentially an aerobic process and, under the most favourable conditions, it would proceed rapidly, as observed in the channel having l-in-50 gradient, and give results attainable only by the activated sludge process. (Our) observations are of scientific interest as well as of practical importance as they not only relate to a sanitary principle in Nature and its bearing, particularly, on the modern methods of sewage disposal but indicate the possibility of increasing the efficiency of the activated sludge process and other methods of aerobic treatment of sewage."

I think it is clear from these results that the natural process can lend itself to acceleration to a good degree. There already exists in the Bangalore region many channels that lead the sewage out of town. (I must add here that the channels have been engineered to make the flow straight. Expert opinion now holds that a meandering flow, being more natural, would have given a chance to the natural processes to work better.) Treatment plants have been erected but they treat only some of the discharge. The natural processes continue, of course, but they may not be able to handle, within practicable flow distances, the heavy load that should, by now, be many times more than what it was half a century ago.

There still exist in Bangalore and its environs several 'tanks,' constructed in earlier, more spacious times, which deserve "restoration, conservation and maintenance." They present a situation ideal for trying out methods relevant to natural clean-up since channels discharge sewage into the 'tanks.' I have on paper what I call a "linear" demonstration project, including rough cost estimates, for forced aeration of sewage flow in the channels to see if protozoa proliferate and form heavy fluffy masses over a short distances because of quickly increased levels of dissolved oxygen. The aim of the project is to see how easily and shortly the Natarajan - Pillai findings can be practicably applied. If the initial test proves successful in clarifying the sewage, in reducing its bacterial content and biological oxygen demand, no reason should stand in the way of going ahead with a full project for utilisation of purified water for replenishing the 'tanks,' for gardening, etc. I assume, of course, that desiltation will be carried out, as is apparently being planned now, and open or clandestine discharge of solid waste directly either into the channels or into the lake water would be declared a cognizable offence .

The project envisages construction of certain civil works of special design along the presently existing channels (hence its description as "linear"), installation of equipment that is not too 'hi-tech,' creation of some collection points for waste materials, etc. Frequent testing of samples in a reputed microbiological laboratory, employing chosen techniques, is an absolute necessity. Even though the costs are expected to be low, convincing the powers-that-be on the need for granting permissions, providing financial support and extending an overall co-operative attitude is expected to present many problems since the project will be of an experimental nature, initially at least. I urge persons present here, capable and being interested and active in the project, to give serious thought to these matters and be of assistance in initiating the it.

I have already said that the Natarajan - Pillai team did not look specifically into the presence of heavy metals and any deleterious effects it may have on the proliferation of the clean-up agents, the protozoa. If anything, the heavy metal content could only have increased since 1960 when the paper was published due to the establishment of diverse industries, which discharge their effluents directly into the channels. The investigation did show, however, that when once clean up has proceeded to an extent, as in the third/fourth zone, water hyacinth begins to grow. I have also referred to the widespread misconception that the presence of water hyacinth is itself "pollution." Numerous investigations have shown, off and on, that water hyacinth can not only lead to the destruction of many toxic materials and absorb heavy metals but can also reduce biological oxygen demand significantly. Harvesting the growth from time to time, burning it for useful heat or subjecting it to the bio-methanation process and disposing off the ashes/residues in a safe way (e.g. at designated sites   from where the toxic materials cannot percolate into the groundwater) are the sensible things to do. Removing water hyacinth ('eradicating it,' as it is often described) is like cutting the head off to cure a headache.

If natural methods as outlined above are adopted and the infrastructure necessary for them to work is in place, the existing sewage collection and lake systems, the really valuable public assets, can be networked. By that I mean: a) one lets in only upgraded sewage into the holding systems for replenishing the storage; b) the holding systems, 'tanks,' would be desilted and deepened; c) overflows will be conducted into the next 'tank' that is at a lower elevation (even by a fraction of meter). Apart from disallowing any direct discharge of raw sewage, dumping of solid wastes by persons who lack civic sense must be declared a cognizable offence. Emission standards must be fixed for industrial effluents and strictly enforced. One has heard of instances where storm water drains are partially covered and the covered area claimed and built over! Obviously, activities of this sort cannot take place without the connivance of those who come to hold power (even temporarily) thinking they can bend the rules.

What I just said would sound utopian and impracticable. But then, if achieved, it is needless to say that the benefit from clean recharging of groundwater would be incalculable.

I began this paper by referring to a writer on ecological matters thanking God for providing Bangalore and its environs with beautiful 'lakes.' I would join him, even while pointing out that the 'lakes' are not natural but man-made reservoirs. I would add, with those thanks, a prayer to the Almighty that S/He should somehow give enough wisdom to those who talk of something called ‘water harvesting,' as if it was something new, and then go about destroying the very facilities created for that very purpose during a more creative past.