A large proportion of the sewage generated in Punjab's towns is discharged untreated into drains, nullahs and ultimately the rivers.
Treatment plants have been built and a significant number operate below capacity or not at all, for want of power, maintenance or connection to the sewer network they were built to serve.
The Buddha Nullah at Ludhiana and the Kala Sanghian drain at Jalandhar are the two best known cases, and both discharge into the Sutlej system.
Villages downstream draw drinking water from shallow hand pumps into the same aquifer.
The Seechewal model, developed at Sultanpur Lodhi, treats village waste water through settlement and filtration and returns it to irrigation, and it is cheap enough to be general and has been adopted in a limited number of villages.
Punjab's rivers carry its towns' sewage, its industry's effluent and, in the dry season, very little else.
It was done with village labour, donated equipment and the authority a dera holds in its own area rather than with a budget. That it worked where departmental schemes did not is a fact about who can get a village to turn out on a given morning, and it is not a fact anybody has managed to convert into policy.
Where treatment plants exist they often lack the sewer network to feed them, so a town can have capacity on paper and untreated discharge in fact.
The drains carry industrial effluent along with sewage, which contaminates the sludge, so even the plants that run properly have nowhere to put what they take out.