The Thames has certainly improved over the last couple of decades, but it is by no means pollution free. Crossing the river on the Woolwich Ferry, as I often do, the water still looks rather grey and uninviting. But there are fish in the river, a fact made obvious by the Comorants which can be seen on the river. Other UK rivers have also seen an improvement in water quality.
One reason for this, I would suggest, is the fact that much of the pollutants which entered our rivers are no longer in use in the UK to the extent that they were in the past. Why is this? The UK, along with many other 'developed' nations, has been using India and other countries such as China, as a source of cheap labour.
Goods which were produced in the UK can be produced far cheaper in India not only because labour is a fraction of the cost of the UK labour force, but also because producers in the UK have had to clean up their act. Flushing contaminated water into the nearest river can bring huge fines on those responsible. Safe and environmentally aceptable treatment of waste can be costly. The cheaper alternative has been to carry out such processes in India, China and other '3rd world' nations, where the cheap labour costs are accompanied by a lack of environmental protection.
In other words, you in India are now experiencing the same environmental disasters that we have seen in the past.
India and China are now regarded as the 'developing' nations. Your economies are growing as you produce more and more of the goods which used to be produced in the west. This may be good for the people of India and China, so long as there is a fairness in the way this wealth is distributed. At the moment, it does not appear to be working very well. BUT, it will come at a great environmental cost if you do not take action to avoid the mistakes we made in the past.
Regulations to protect the environment are essential and need to be introduced NOW. The problem is that such regulations will increase your manufacturing costs and thereby slow down your growth. That is a prospect which politicians in India will be reluctant to face. Industry will do all it can to prevent any regulations it deems to be harmful to its growth.
India is a democracy and its people must decide what they want. I would suggest that you accept a slower growth rate in return for better wages for all, so that individuals can afford to act responsibly and industry be forced to act on protecting your environment, regardless of cost, so that you do not have to pay a much higher price in the future. In communist China it doesn't look as if things are going to change any time in the foreseeable future.
The west has taken advantage of India and other similar nations, for many years. Now India is in a strong position to counter this. Make the most of it and learn from the mistakes we have made.