Sewage Treatment

Human health and environment are mainly suffering from direct disposal of commercial and human effluents into the natural resources with none of the treatment. The sewage treatment is important to scale back the toxicity of sewage and maintain a secure and healthy environment, also as it promotes human welfare.

Sewage Treatment Process

Sewage contains an enormous amount of organic matters which are toxic. Microorganisms are widely utilized in the sewage treatment plant for removing this toxic organic matter. Sewage or wastewater treatment plant consists of two stages:

• Primary Treatment

It involves the removal of huge or small sized components within the wastewater through physical processes.

• Biological Treatment

The sewage treatment plants are inoculated into Aerobic microorganisms .These  organic components of these microbes utilize the sewage and reduce the toxicity which can be measured by BOD (Biological oxygen demand).

After the biological treatment, the sludge is pumped from the treatment plant into an outsized tank. This large tank consists of anaerobic bacteria which cause the digestion of sludge. During digestion, biogas is produced and it is used as an energy source. Hence, Sewage treatment plant design and sewage management play an important role within the maintenance of human welfare.

Energy Generation

Microorganisms which are involved within the production of energy are called microbial fuel cells. Microbial fuel cells are used to generate a variety of energy sources like biogas and electricity. Agricultural waste, manure, and domestic wastes are used as raw materials for the generation of biogas. Biogas generation is completed within the large concrete tank which is named as a biogas plant.

Biomasses (Biowastes) are collected at the biogas plant and therefore the slurry is fed. Biomasses are rich in organic matter. Some of the bacteria inside the biogas plant anaerobically These bacteria can digest the biomasses which are present within the slurry and sewage. During digestion, an enormous amount of mixture of gases is released inside the tank. The mixture of these gases is called biogas. Biogas is removed from the biogas plant through a separate outlet.

Electricity from wastewater can also be generated by Microbial fuel cells. From the wastewater treatment plant microbial fuel cells utilize the organic matter.During digestion, organic matters are converted into the straight molecule and release the CO2 and electrons. Those electrons are absorbed by the electrode and used as the source of electricity.

Odor Control 

Odors emitted by sewage treatment are typically a sign of an anaerobic or "septic" condition. Early stages of processing will tend to supply foul-smelling gases, with sulfide being commonest in generating complaints. Carbon reactors, a contact media with bio-slimes, less doses of chlorine, or circulating fluids to biologically capture and metabolize the noxious gases at plants with large processes in urban areas are the processes that are used to fade away the foul odor. Other methods of odor control exist, including addition of iron salts, peroxide , nitrate, etc. to manage hydrogen sulfide levels. High-density solids pumps are used for minimizing the odor by conveying sludge through hermetic closed pipework.

Environmental Aspects

There are many processes that are used in the wastewater treatment plant that are designed to copy the natural treatment processes that occur within the environment, whether that environment may be a natural water body or not. Bacteria within the environment will consume organic contaminants if not overloaded,although this may lead to the reduction of the amount of oxygen within the water and should significantly change the general ecology of the receiving water. Organic contaminants work as a food for the neighbouring bacterial populations and therefore the numbers of disease-causing microorganisms are reduced by natural environmental conditions like predation or exposure to ultraviolet . 

Consequently, in cases where the receiving environment provides a high level of dilution, a high degree of wastewater treatment might not be required. However, recent evidence has demonstrated that very low levels of specific contaminants in wastewater, including hormones (from farming and residue from human hormonal contraception methods) and artificial materials such as phthalates that mimic hormones in their action, can have hit or miss adverse impact on the natural biota and potentially on humans if the water is reused for drinking water. As per the law in the US and EU, uncontrolled discharges of wastewater to the environment aren't permitted under law, and strict water quality requirements are to be met, as clean water is essential. A significant threat within the coming decades are going to be the increasing uncontrolled discharges of wastewater within rapidly developing countries.