In the previous article we mentioned the importance of carrying out water treatment and the first phase to eliminate polluting substances, so in this text we present the final phases of this process: secondary and tertiary.
The secondary treatment consists of reducing the biological and chemical levels of contamination through a treatment of neutralization and elimination of microorganisms in Wastewater Treatment Plants (WWTP) or Wastewater Treatment Plant (WWTP), according to the specifications and needs of the liquid, where we find anaerobic and aerobic processes. In anaerobes, processes such as activated sludge, anaerobic digestion, bacterial beds and aerated lagoons are used, as well as other methods to eliminate solid remains.
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Likewise, it is important to consider that, if the water that will be received in the discharge needs a higher degree of treatment, an advanced treatment must be used to improve the quality of the water and counteract any persistent contaminant. Meanwhile, tertiary treatment aims to eliminate pathogens such as phosphorus, minerals, heavy metals, nitrogen and viruses. Reverse osmosis and electrodialysis are applied here to dissolve solids, as well as ozone treatment to disinfect.
Pouring of liquid
It is necessary to know the municipal and industrial discharges. The first are native to urban areas such as houses, public and private spaces; On the other hand, the industrial ones, as their name indicates, come from the industries. The final discharge of the treated water is carried out in different ways. Direct discharge into a receiving river or lake is the most common. Water-scarce places employ reuse of treated water to replenish aquifers, irrigate non-edible crops, as well as in industrial processes.
Let’s see the following example for residential drinking water: “the conventional process is carried out: primary and secondary, followed by lime cleaning to eliminate organic compounds in suspension. During this process, an alkaline medium (high pH) is created to enhance the process. In the next step, recarbonation is used to return to a neutral pH. The water is then filtered through multiple layers of sand and charcoal, and a component such as ammonia is removed by ionization. Pesticides and other organic compounds still in suspension are absorbed by a granular activated carbon filter. Viruses and bacteria are removed by ozonation. At this stage the water should be free of contaminants, but for greater safety, the second stage of absorption on carbon and reverse osmosis are used, and finally chlorine dioxide is added to obtain maximum quality water.
The following table summarizes the processes of the types of treatment that we have analyzed.
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