Effluent and Sewage Treatment in India- The Causes, Problems & solutions to India's Water, Sewage & Effluent Treatment

Effluent and Sewage Treatment in India

The causes of, problems created by and solutions to india’s water, sewage and effluent treatment problems

Foreword

During my summer break in 2017, I decided to spend two weeks as an intern at XYZ Water Projects and Water Solutions to understand effluent and sewage treatment plants and learn more about the engineering involved in planning and commissioning these plants. I was overwhelmed by the need for effluent and sewage treatment and realized that people often take manufactured goods and commercial complexes for granted without realizing how much effluent and sewage treatment is required for such facilities.

Taking the mission of xyz[footnoteRef:1] beyond drinking water, XYZ Water Projects was established to offer packaged and customized, total water and waste water treatment solutions. These optimized solutions are membrane[footnoteRef:2] based, or based on other cutting-edge technologies, and they all deliver treated water suitable for diverse water utilization purposes and industrial process requirements. [1: ] [2: a thin pliable sheet of material forming a barrier or lining]

Complementing xyz’s world-class solutions are Desalination Plants, Effluent Treatment Plants, Waste Water Recycle Plants, Water Treatment Plants, Sewage Treatment Plants, Zero Liquid Discharge Plants (ZLD)[footnoteRef:3] and other tailored solutions. [3: A zero-liquid discharge plant is one that converts all input wastewater into reusable water]

As a result of the impact my time at XYZ had on me, I decided to make a report on effluent and sewage treatment in India and XYZ’s Water Solutions and Water Projects Divisions.

Industrial Pollution and Effluent Treatment

What comprises Industrial Pollution and Effluent

Industrial pollution is the release of wastes and pollutants generated by industrial activities into the natural environments including air, water, and land. Specifically, in terms of water, any industrial process that requires an input of water, either to manufacture the product, run machinery, or carry away waste, emits a large amount of heavily polluted water that contains industrial waste (an effluent) with harmful chemical components that make it extremely damaging to the water they are discharged into.

Water that is discharged from manufacturing plants often contains harmful chemical materials like strong acids, oils and greases, and semi solid materials like sludge[footnoteRef:4] that is created as a result of industrial processes. Such polluted water is foreign to natural water sources like lakes, seas and rivers into which this polluted water is eventually discharged. There are several negative effects of industrial water based pollution, but, amongst them, what is perhaps most prominent is the fact that large amounts of water that could be reused are being wasted, and other fresh water that could be used is being polluted as well. [4: thick, soft, wet mud or a similar viscous mixture of liquid and solid components, especially the product of an industrial or refining process]

Industrial Waste is normally divided into two categories – Process wastes and Chemical Wastes. The waste generated in an industry during washing and processing of raw materials is known as process waste. The process waste may be organic or inorganic in nature depending upon the raw materials used and nature of the industry.

The organic process wastes are liberated from food processing units, distiller­ies, breweries, paper and pulp industry, sugar mills etc. The inorganic process wastes may be the effluents of chemical industries; caustic soda industry, paint industry, petroleum industry, pesti­cide industry etc. Both organic and inorganic process wastes are toxic to living organisms.

The chemical substance generated as a by-product during the preparation of a product is known as chemical waste product. The chemical waste includes heavy metals and their ions, deter­gents, acids and alkalis and various other toxic substances.

These are usually produced by the industries like fertiliser factories, paper and pulp industries, iron and steel industries, distilleries, sugar mills etc. These are usually liberated into nearby water bodies like rivers, lakes and seas and sometimes into lands. The entry of these chemicals into bodies may alter the pH, BOD (Biological Oxygen Demand)[footnoteRef:5] and COD (Chemical Oxygen Demand)[footnoteRef:6]. [5: Biochemical oxygen demand (BOD, also called biological oxygen demand) is the amount of dissolved oxygen needed (i.e., demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.] [6: Chemical oxygen demand (COD) is a measure of the capacity of water to consume oxygen during the decomposition of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite.]

Image 1 - Untreated Effluent being released into a water body

Industries that cause Industrial Pollution

· The Textile Industry - The textile industry is one of the oldest industrial sectors in the world. Textile industries consume large volume of water and chemicals for wet processing of textiles. The effluents from textile units have various types and qualities of wastewater. The wastewater from printing and dying units in a textile plant are often rich in color, containing residues of coloring agents and chemicals, and needs appropriate treatment.

· The Tannery Industry - Tannery operations involve conversion of raw hides or skins into leather, a stable material, which can be used for manufacturing of large number of products. The tannery industry is a water and chemical intensive industry, wherein, a large number of complex chemical and mechanical processes are involved. These industries are one of the most polluting industries causing pollution in the environment.

· The Pharmaceutical Industry - The pharmaceutical industry produces organic based wastewater, which requires treatment. These high strength industrial wastes are often difficult to break down in conventional wastewater treatment processes. The high COD values and recalcitrant nature of some of the organic compounds present are characteristic of Pharmaceutical wastewater streams. Its treatment poses one the biggest challenge to the industrial waste treatment system because of the lack of homogeneity of the effluent; there is no single approach or treatment method that applies to all.

· The Electroplating Industry - Electroplating industry in India is spread throughout the country. They are mainly in small scale sectors with over 3,00,000 small scale units. The pollutants from the electroplating industries are invariably hazardous, as the effluents contaminate air, water and soil. Some of the polluting agents have deleterious effect on human health, examples being cadmium, lead, nickel, etc. The environmental load in electroplating industry mainly consists of process waste water, hydroxide sludge and sulphuric acid. The untreated rinsing water has a lot of waste.

Increase in Pollution in India

What is perhaps the most disturbing aspect about the wastewater conundrum in India is the staggering rate at which pollution in major cities is increasing. The number of manufacturing industries in the country is growing rapidly and, with it, comes an increase in the number of polluting factories. While such factories and industries might boost the economy and strengthen India financially, the environmental implications that it has can easily nullify and even outweigh the economic benefits of such a factory.

Image 2 - Statewise Generation of Sewage (Source - sulabhenvis)

The problem with capacity – why India needs more treatment plants

While the growth in pollution over time is an obvious result of the industrialization, it should follow that India has developed equally fast in terms of its ability to treat sewage and effluent. However, there is a monumental mismatch between the rate at which water is being consumed and polluted and the rate at which it is being treated. Although implementation of other technology is a major cause of the industrial pollution and effluent let out in water, India doesn’t have even nearly enough effluent treatment plants to deal with the amount of waste generated. Hence, the problem lies not only in the quantities of waste being produced but also in India’s inability to treat these large quantities of waste. The inability to treat this waste is, eventually, the primary cause of pollution to fresh water bodies and the fundamental problem with manufacturing in India.

It is clearly visible, from the table above, that there aren’t enough common effluent treatment plants in the country to treat all the chemical waste that is generated in the country. Comparing the number of common effluent treatment plants in each state with the percentage of chemical sewage they generate (as per the above pie chart) reveals some disturbing figures. West Bengal, for example, has merely one common effluent treatment plant despite being the fourth most polluting state in the country. Hence, Effluent Treatment in the country needs to be improved manifold if India is to progress in terms of infrastructure and manufacturing goods.

Sewage in India – Domestic and Commercial Waste

What comprises Sewage

Sewage (or domestic wastewater or municipal wastewater) is a type of wastewater that is produced from a community of people. It is characterized by volume or rate of flow, physical condition, chemical and toxic constituents, and its bacteriologic status (which organisms it contains and in what quantities). All sewage ends up back in the environment (from which its constituents came), by any of several routes. A basic distinction in its route is whether it undergoes sewage treatment to mitigate its effect on the environment before arriving there. Sewage usually travels from a building's plumbing either into a sewer, which will carry it elsewhere, or into an onsite sewage facility.

Image 3 - The effect of sewage on a nearby waterbody (Source - The Guardian)

The need for sewage treatment – Growth of Urban Slums

Despite the rapid development of India in the past decade, there has been a marked increase in the number of people living in urban slums.

Image 4 - The growth of Urban Slums in India

A large number of these urban slums are unorganized and dispersed, and almost none of their waste flows through a sewage treatment system. Given the massive slum-dwelling population in India, this causes catastrophic damage to the environment. The toxic chemical and bacterial content of this sewage is extremely damaging to all aquatic life and the high biological and chemical oxygen demand of this sewage chokes whatever water body is dumped into.

How waste remains untreated - Why inaction is no longer an option

Official figures show that 78 per cent of the sewage generated remains untreated and is disposed of in rivers, groundwater or lakes. Eighty per cent of water leaves homes as sewage. Since cities do not have any accounts of the sewage they generate, they cannot plan and do not have the capacity to treat all the sewage they generate. This has the gravest implications for rivers where the faecal sludge is dumped. Lack of treatment options lead to two problems: not treating wastewater before discharging it into waterways pollutes the source, often rendering the water unusable for drinking. The water intended for drinking is withdrawn from this same source, and again not adequately treated, creating significant public health problems: 21% of communicable diseases in India stem from unsafe water. A Yale University study released in late January ranked India 124th out of 178 countries on the 2014 Environmental Performance Index (EPI) in terms of access to water and sanitation. According to India's Central Pollution Control Board, the country has an installed capacity to treat only about 30% of the household waste it generates, and only 22% of the waste is actually treated – the rest is released into open drains or straight into the ground.

A city wise analysis of how equipped India is to manage the enormous amounts of sewage that it produces reveals that only three of the thirty-five metropolitan cities in the country even have the capacity to treat all their sewage, while others, like Bhopal, Lucknow, and Jaipur have the ability to treat less than 15% of their total generated sewage.

The Treatment Process – An overview of Sewage Treatment

Preliminary treatment

Preliminary treatment is required to remove the coarse solids and other large materials from raw wastewater. Removal of these materials is necessary to enhance the operation and maintenance of subsequent treatment units. A number of unit operations are engaged in the preliminary treatment of wastewater to eliminate undesirable characteristics of wastewater. The operations include use of screens and grates for removal of large materials, comminutors for grinding of coarse solids, pre-aeration for odor control. Sometimes pH correction and removal of oil & grease is also done.

Image 5 - A schematic of preliminary treatment

Primary treatment

Primary wastewater treatment, at times, is the first step in the wastewater treatment process or it may be the second step after the preliminary treatment. It involves physical separation of suspended solids from the wastewater using primary clarifiers. This process is helpful in reduction of total suspended solids (TSS) and associated biochemical oxygen demand (BOD) levels and prepares the waste for the next step in the wastewater treatment process. The objective of primary treatment is to remove of settleable organic and inorganic solids by sedimentation and removal of materials that float (scum) by skimming. Approximately 25 to 50% of the incoming biochemical oxygen demand (BOD5), 50 to 70% of the total suspended solids (TSS), and 65% of the oil and grease are removed during primary treatment. Some organic nitrogen, organic phosphorus, and heavy metals associated with solids are also removed during primary sedimentation but colloidal and dissolved constituents are not affected. The effluent from primary sedimentation units is referred to as primary effluent. Primary treatment ensures satisfactory performance of subsequent treatment units. Sedimentation chambers are the main units involved but various auxiliary processes such as fine screening, flocculation and floatation may also be used. The second step may be chemical treatment (generally with lime and alum) which is sometimes preceded by flocculation. The purpose is to remove metals by precipitation but it also removes some associated colloidal BOD. The process generates chemical sludge.

Image 6 - A schematic of primary treatment

Secondary Treatment

This process involves decomposition of suspended and dissolved organic matter in waste water using microbes. The mainly used biological treatment processes are activated sludge process or the biological filtration methods. Biological treatment processes mainly used for secondary treatment and are based on microbial action to decompose suspended and dissolved organic wastewater. Microbes use the organic compounds as both a source of carbon and as a source of energy. Biological treatment can be either aerobic where microbes require oxygen to grow or anaerobic where microbes grow in absence of oxygen or facultative where microbes can grow with or without oxygen. Micro-organisms may be either attached to surface as in trickling filter or be unattached in a liquid suspension as in activated sludge process.

Image 7 - A schematic of secondary treatment

Page 1