Effluent Treatment Plant: An Exigency to Prevent Water Pollution by Abdullah Al Moinee

Effluent Treatment Plant: An Exigency to Prevent Water Pollution 

Abdullah Al Moinee 

Water is the most essential element of the earth to fuel the flow of life. The eternal element is the sacred soul of earth and the essence of all existences. Life on earth would not exist without the presence of water. Earth has the right to sustain the lives nurturing them without being polluted. According to the World Atlas 2018, only 3% of the water occupying 70% of the earth’s surface, is considered as fresh water where 2.6% is inaccessible for human being. This leaves us with approximately 0.4% of the earth’s water which is usable and drinkable to be shared among the billions of inhabitants. As a consequence of inadequately planned industrialization, large amounts of wastewater containing organic matter and toxic heavy metals are discharged into the water bodies on a regular basis. This discharge poses a serious threat to ecosystems, aquatic life, and human health. The pollution not only contaminates water but also pollutes the air and soil which jeopardize human beings, plants, animals, fishes and even the small bacteria. The deterioration of a water body due to the discharge can be alleviated by adopting sensible steps. Effluent Treatment Plant (ETP) can contribute securing the steps to meet the exigency of the earth preventing water pollution. 

Effluent is an out flowing of water or gas which is defined as the liquid waste or sewage discharged into a river or the sea. Many kind of industries e.g. textiles, tanneries, pulp and paper industries, food industries, iron and steel mills, mine and quarries, refineries, power plants produce wastewater from the production. In the production processes different kind of raw materials are applied that goes through robust reactions which results in the products and byproducts. The wastewater (effluent) as a byproduct of industrial production contains the toxicity of different microbes, soluble organics, dye, ammonia, salts, cyanide, hydrogen sulfide, protozoa, pesticides, carbon-dioxide, methane, and heavy metals e.g. arsenic, mercury, lead, cadmium, chromium, zinc most of which are dangerously detrimental to health and environment. Therefore, the effluent needs to be treated before discharging them into the environment for preventing the pollution. According to an industrial survey conducted by Bangladesh Center for Advanced Studies (BCAS) in 2009, only about 40% industries have ETPs (Effluent Treatment Plants) in our country. In 10% industries, ETPs are under construction and about 50% industries have no ETP establishment. That is, more than 50% of waste generated by the industries eventually goes to the rivers untreated. According to the Environment Conservation Act, 1995 (Amendment 2010), factories which are in “red category” are bound to install and run an ETP. Later, Institute of Water Modeling (IWM) and the World Bank conducted a survey of pollution in Dhaka Rivers in 2007 that showed there are over 300 various effluent discharge outlets in the capital. There are about 149 tanneries in one of locales of Dhaka city which daily generate about 18,000 liters liquid and about 115 metric tons solid waste almost all of which get released into the river Turag. The Tongi Industrial Area, other extreme pollution premises, possesses about 29 heavy industries. This cluster of industries of the capital city generates 7,159 kg effluents daily (IWM, 2008). Thus, ETP is an urge to be implemented by each of these industries. 

There are different kind of ETP plants are being installed on the combinations of physical, chemical, and biological unit operations. In a general operation of ETP, the wastewater as by-product flows from the main factory to the equalization tank sustaining a process of aeration. Thus the oxygen deficiency in the waste water is gradually reduced when pH and temperature are also maintained simultaneously. Then the biological treatment plant unit is followed by the equalization tank where activated bacteria are added to the water. Bacteria grow around some plastic rings to remove the impurities from the water through their metabolism. The process eventually reduces the biological oxygen demand (BOD) and chemical oxygen demand (COD) removing the organic pollutants from the wastewater. Later, the biologically treated effluent goes to the chemical treatment plant for coagulation and flocculation where chemical reagents are to be added to control the pH. There, small suspended particles join with one another and become heavier. Then the addition of polyelectrolytes with mechanical agitation makes the granules even bigger which triggers the separation of the particles and the liquid. As the suspended particles get heavier, they gradually moving down, and the water becomes cleaner at the top. Solids are separated from the liquid and taken to the tube settler. After settling the water in tube settler, the water is brought to two more filters. One is pressure sand filter and other is activated carbon filter. In the pressure sand filter, there are stone packs, at the bottom and sand above it. When the water is pumped and passed through the sand, suspended solids are trapped inside. Activated carbon is an effective adsorbent because it is a highly porous material and provides a large surface area to which contaminants may adsorb. Thus activated carbon adsorbs natural organic compounds, dyes, odor compounds, and synthetic organic chemicals from the water. Finally, the water is considered fully treated and it is flown outside. The solids are passed from tube settler to sludge thickening tank. When it reached at a particular density, the sludge is pumped to the filter press where liquid and solid gather at the center. Liquids are pushed out using pressure so solids are left there as cakes. Eventually the water goes out and the sludge is stored at the bottom. The water flows back to the original drain and the solids are carefully stored in the drums. Later, the stored sludge is disposed-off or reused as bio-solids in agricultural fields after proper stabilization processes of composting or anaerobic digestion. 

In environment–economic theory, pro-environmental behavior is not considered rational as it is assumed that individuals act to pursue only their own short-term economic benefits. In many cases, engineers and managers are considering their financial aspects over the environmental disaster fading the ethical aspects. Therefore, the theory concludes that state penalties or subsidies are essential to manage environmental and resource problems. Regarding penalties, monitoring and enforcement have been implemented in Bangladesh, although they are inadequate and not sufficiently institutionalized. The findings of researchers suggest that it is not so difficult for companies to install and operate ETPs in terms of the cost. Besides, financial solvency is not a barrier. Therefore, by making the monitoring and regulation strict, environmental compliance could be achieved for those who can afford to purchase and operate ETPs. In addition, the dominant barriers to ETP installation are at the purchase stage, rather than the construction stage: ETPs are unavailable in local markets and the import tax is high. Institutional arrangements are required to improve this situation which could include establishing a subsidy scheme that would encourage voluntary construction of central ETPs. To encourage setting up ETPs, the central bank of Bangladesh has given directives to other banks to provide low interest loans to industries for setting up ETPs. Some banks have taken initiatives in this regard. Even though some money needs to be invested to set up an ETP, in the long term it brings better customer satisfaction and a strong goodwill for the industry. To maintain this consistent growth, there is no alternative but to create a safe and environment favorable work place for all. Setting up ETPs is an important step in securing that which can contribute to create a good environment and progress of the industries. It is very hopeful that some industries in our country are installing effluent treatment plants to treat the wastewater and conserve the environment. 

Clean water-body is an oasis in the premises of pollution and so prevention of water contamination is the key for conserving a sustainable future. In earth, life depends on water but the reservoir depends on the inhabitants. The water people pollute will find its way back to them. So, the industry should escalate their awareness by working in agreement with the environment. The transformation of production technology, in connection with the environmental safety, which is mandated by the pollution prevention creates a new surge of economic development. It goes without saying that the industrial revolution is a great engine to accelerate the economic growth of any country. It also contributes greatly to reduce the unemployment problem. When the industrialization strengthens the economic growth of the country, it is a matter of great concern that the production process of these industries pollutes the water bodies of environment at an alarming rate. The untreated wastewater from the industries have deleterious effect on environment that can engender extinction and damage bio-diversity. So, there is no alternative but to set up ETPs, treating the wastewater of the factories with a view to sustaining the impulse of industrialization. The impulse will then sustain the shield against the pollution to protect the water of this earth as the essence of our lives.