Every society must understand how the excreta it produces is managed. It teaches us many things about water, about waste, about technologies to clean, economics and politics: of who is subsidised to defecate in our societies. But, most importantly, it teaches us humility. We know so little about our own world. If we knew better, we would understand why we are failing to ensure our present and why we will all need to do things differently, if we want to safeguard our future.

I learnt about excreta management by chance. A few years ago, the Supreme Court asked the committee I work with to monitor the state government's effort to clean city drains, which lead to the river and pollute it to hell. The government presented an action plan. They would build sewage treatment plants; upgrade existing ones; lay sewage drains in housing colonies and repair conveyance systems to pump the waste to sewage plants. It fitted prescriptions for pollution management of our rivers.

I presumed our task was to check if the sewage plants had been built and if they were working. How ignorant of me.

My first lesson came when we visited the sewage treatment plant. The plant's management had records of the quality of waste received and the treated effluent. They showed us samples as well. It seemed to be in order. The only, small, problem was that the sewage plant remained underutilised - it received only 40 per cent of the waste that it could treat. Officials told us that this was because the sewage systems and drains were laid but had not been connected by households, because of high costs. They said it was only a matter of time when the infrastructure would be completed and sewage would flow into the plant. Their emphasis was to add to the infrastructure of the sewage plant itself. They needed more capacity in anticipation of this additional sewage that would be generated. Once done, the river, they assured us, would be clean.

Made perfect sense. Then, by chance, I asked how they disposed the treated effluent. Pat came the reply: we have a treated effluent disposal drain, which meets the river at some distance. This is what happens in most cities, - I was reassured. My colleague, a senior and respected bureaucrat, and I then wanted to see the disposal point. Immediately, a can of worms opened.

The disposal point was in the drain in front of the sewage plant. From where we stood, it was clear that the treated effluent - meeting all pollution parameters and costing money and electricity to clean - was discharging into a drain, which was already putrid and full of sewage. The treated effluent did little to dilute the floating filth. In fact, the stuff in the drain negated the pollution control efforts. The plant had been built where land was available. The officials had never considered how the treated effluent would be disposed and if indeed it could be reused.

Then we asked about the drain. It was a storm water drain and the official told us that it should not have any waste (it was peak summer). The problem was that the adjoining colonies did not yet have sewage drains but once they did, the situation would be under control.

Then another can opened. We learnt that roughly half the population residing in this part of the city were not connected to the sewage system. They lived in illegal, unauthorised or slum areas. So their waste was also "illegal", not to be unaccounted for. This is not unusual. In most big cities of this country, 20-50 per cent of the people live in similar settlements. Since official drainage does not effectively connect the entire population, only partial sewage is trapped, pumped and taken to the conveyance system. Their sewage gets carried by gravity to the open drains, which in the official books only transport storm water, not excreta. The pieces fit together when we understand that this "legal" and "illegal" sewage gets mixed in the same drain, which by the time it meets the river is grossly polluted. No wonder the river never gets cleaned.

The next sewage treatment plant is located downstream of the first. It retreats the effluents discharged from the first plant, which has turned dirt to dirt. The treated effluents of this plant then meet another drain, which collects more sewage on its way to the river.

The problem gets even more serious as we get to the river. The river is tapped at the barrage upstream of the city, for drinking water. Then, in its journey, it picks up sewage from my city. By the time it exits, it has only sewage, no water. The cities downstream of my city do the same. The river has no water to dilute our excreta. It is even losing its assimilative capacity - to turn sewage - to soil and water. To bring it to life would require us to take water and to return water to the river.

I now understand the economics of the excreta business. Put out a tender and build drains, pumps and sewage treatment plants. The problem is we don't know our maths. The more water we use, the more waste is discharged. The State does not charge for the water it supplies, forget for the waste it collects or treats. The relatively rich - or call them "legal" settlers with "legal" excreta - cost the State. It does not have money or the wherewithal to pay to build, or run, or repair the system for all. There is no way the river cannot get polluted.

This is not a parody. The city of Delhi, from where I write, has the river Yamuna, which flows past it. But this water-excreta tale is not unique to Yamuna or Delhi. This is the political economy of defecation where the rich are subsidised in the name of the poor, where the environment is discounted in the name of progress. This is the real excreta we must understand.

- Sunita Narain
PS: For more, read our book Sewage Canal: How to clean the Yamuna