For many years we are consuming on credit: the resources of the planet are diminishing as the population increases, and the rare commodities like water are more and more wasted. Currently only the two percent of used water in the world are recycled, which is derisory compared to the human consumption. But since a few time people seem to start to realize that the respect of the environment is vital for the human race survival, and the consumer habits are changing a bit: the water treatment plants are becoming more and more numerous, and enable to recycle more wastewater.
The steps of water treatment
Before becoming suitable for consumption again, the water has to be subject of a specific eight-step treatment: firstly it is screened to remove the biggest impurities, then it is degritted and degreased. After it is treated a first time with chlorine to eliminate the noxious chemical compounds, then it is aerated to bring oxygen to it. Then it is clarified, that is to say filtered in a big sedimentation tank with a sieve to allow the impurities to fall at the bottom, and it is the subject of a tertiary treatment with chlorine and ozone. This last step can be repeated once to completely purify the water. Once the water is treated, the sewage sludge is collected, that we also have to treat to be reused.
The sewage sludge treatment
Firstly the sludge which is collected after the water treatment has to be thickened to increase its dry matter content, then it is dehydrated to remove the maximum of water. After it is dried out and stabilized to prevent the development of bacteria responsible for bad smells. Finally it can be stored and sent to other places to be reused. If you want to go further, click to learn more about urban and industrial sludge.