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3 Reasons why sewage treated water becomes non reusable

When we talk about sewage treatment plants, we can generalise all the sewage treatment plants to be the same. Each sewage treatment plant has its own technology and modifications, like MBBR, SBR, FBR, MBR, and many more. There are many pros and cons to each technology, but the result for all the treatment plants is that both CAPEX and OPEX should be less and produce the best result. The maintenance and operations of the treatment plant also should be simple and not complicated. Otherwise, the treatment plant becomes challenging to maintain. Also, sewage treatment plants should be having enough retention time. If not, there will not be enough time for the biological process to happen. Multiple factors affect the operation of the treatment plant.



Let us look into 3 of the most common reasons why a sewage treatment plant does not work.



1st Reason – All the Biological processes must happen



Two primary biological processes need to happen in the sewage treatment plant. Most of the treatment plants have an aeration process where organic compounds break down into four phases. After this, Nitrification and de-nitrification happen to remove the nitrates in the water. During all these processes, the pollutants or suspended gets removed. The contaminants are from domestic usage from Toilets, Kitchens and Laundry. Clients can use the water after the Nitrification and De-nitrification processes for different purposes.  The client can use the water for flushing; it has to be disinfected by chlorine or ozone. Suppose any one of the processes does not work. The water will not be reusable.



2nd Reason – Undersizing the treatment plants



One of the most common reasons that we observed is that the sewage treatment plant is primarily undersized. The tanks are not able to hold and treat a  days flow; some of the significant reasons are

  1. Miscalculation of the flow,
  2. some times increase in the flow,
  3. Unable to maintain the microbes required for the treatment to happen.


These reasons lead to improper treatment of plants. As a reason, the treatment does not happen, and the water becomes unusable. As pollutants are still present in the water, precautionary filters are used to remove the contaminants. Even with filters, parameters will not be met if the biological treatment does not happen and the water becomes unusable. So it is always to check whether there is enough space left for all the treatment to occur.



3rd Reason – Not enough tertiary treatment



Once all the biological treatment is complete, it is also essential to have excellent tertiary treatment. Chlorine is majorly used for disinfection; for one-time use, it is good. If you have to reuse it multiple times as chlorine reacts with pollutants. For this reason, also we have to use filters to remove the contaminants for use, which increases the cost to run the plant. So it is advisable to avoid chemicals in the design beforehand to avoid removal of it later.



In OxyO, we ensure that enough retention time is given for all the processes, and we do not use any chemicals in our treatment plants. That makes the water quality suitable, and we can reuse the water multiple times.





Arun Karunakaran


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