Introduction

Abstract

Freshwater is an imperative normal asset that will keep on being sustainable as long as it is well managed. In many parts of the world, rapid industrial development have prompted to an intensive and still increasing utilization of water resources. Industries are one of the most important pollution sources around the world. The discharge of untreated or improperly treated wastewaters from industries into water bodies may contain very diverse groups of hazardous pollutants depending on the nature of industry. The industrial waste waters may have undesirable color, odour, acids, alkalies, organic matters, toxic chemical contents, heavy metals, pesticides, oils, high biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS) etc. These pollutants may pose a serious threat to all life forms. It is, therefore, necessary to treat the industrial waste water prior to their disposal into water bodies. The conventional industrial waste water treatment processes such as precipitation, adsorption, oxidation, filtration etc. have long been established in removing many hazardous pollutants but these methods have their own limitations. These methods are expensive, and require complex processes and maintenance. Biological treatment process is an important and integral part of any wastewater treatment plant. Different taxonomic group of microorganisms (bacteria, fungi and algae) and plants play a major role in the biological treatment of industrial wastewater. The fresh water demand in current and future prospects could be met by improving the efficiency of water usage and demand management. The recycling and reuse of industrial wastewater is emerging as potential source for demand management and water shortage after essential treatment.

Rapid industrial growth, urbanization and population explosion are the major contributor of environmental pollution throughout the world. Environmental pollution is a vital concomitant of the activities of man. Wherever we find man, we fundamentally find wastes. These wastes have got to be disposed off and when they are inadequately dumped into the ocean or a river, water resources are contaminated which may pose risk to the aquatic animals and human life. Water has a broad impact on all forms of life. It is a vital natural resource for agriculture, manufacturing and many other human activities. Despite its importance, water is the most poorly managed resource in the world. The accessibility and quality of water always have played an important role in determining the quality of life. There is restricted possibility of an expansion in the supply of fresh water because of competing demands of expanding populations all over the world. Lack of fresh water supply is likewise an aftereffect of the misuse of water resources for domestic, industrial, and irrigation purposes in many parts of the world. Water has certain physical, chemical and biological properties in its natural state. Industrial wastewater may be altering the properties of water which may become unfit for consumption. During the past few decades rapid industrial development has become an important contributor of a country high economic growth. With the development of different industries a large amount of fresh water is used as a raw material. These industries produce a large quantity of wastewater as an essential by-product of modern industry which contributes to water pollution. The surface water is the main source of industries for waste disposal. Water pollution due to improper disposal of untreated industrial effluents into water bodies is a noteworthy issue in the worldwide context. The pollution caused by the release of industrial effluents into the rivers and streams has created the issue of general wellbeing as well as a social issue.

Industrial wastewaters are effluents released from industries which are associated with raw-material processing and manufacturing. Most of the wastewater generating industries include pulp and paper mill, tannery, dairy industry, distillery, winery, sugar mill, textile industry, pharmaceutical industry, oil refinery/petroleum industry, beverages/soft drink bottling industry etc. The wastewaters from these industries may not be safely treated due to the lack of highly efficient and economic treatment technology. Untreated or improper disposal of wastewater have increased the level of surface water pollution resulting in adverse effects on the quality of all forms of life.

1.1 Characteristics of Industrial Wastewater

The wastewaters released by the industries are variable in their composition depending on nature of industry and contaminants. Each industry produces its own particular combination of pollutants. The industrial wastewaters are characterized in terms of their physical (total solids, suspended solids, dissolved solids, color, odour and temperature), chemical (inorganic and organic), and biological characteristics (Table 1.1).

Table 1.1 General characteristics of industrial wastewater

There are various contaminants in industrial wastewater, with organic pollutants constituting the critical part. Numerous organic compounds such as aliphatic and hetercyclic compounds, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, herbicides, phenols are incorporated in the industrial wastewater. Many inorganic compounds (phosphates, nitrates, sulphates) and heavy metals (Cd, Cr, Ni, Pb) are also present in the industrial wastewater. Large amount of pollutants in water bodies cause an increase in biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS) and total suspended solids (TSS). BOD and COD represent the gross amounts of organic matter and their constituents in wastewater (Fig. 1.1). The pollutants from the discharge are directly related to the nature of the industry. For instance, the wastewater released from textile industry have high COD, BOD and color whereas wastewater released from tannery industry have high concentration of metal such as chromium and cadmium (Table 1.2).

Fig. 1.1

Organic constituents of wastewater

Table 1.2 Characteristics of various industrial wastewaters

1.2 Environmental Hazards of Industrial Wastewater

Industrial wastewater is one of the important sources of water pollution. The discharge of industrial wastewater into rivers, lakes and coastal areas resulted in serious water pollution problems and caused negative impacts on the ecosystem and human beings. The industrial discharge carries various types of pollutants such as organic matter, suspended solids, inorganic dissolved salts, petroleum hydrocarbons, heavy metals, surfactants and detergents. These pollutants may pollute receiving water bodies rendering them unsuitable for drinking and irrigation as well as they adversely affects the humans, animals, plants and aquatic life (Table 1.3). Industries produce and utilize a large number of synthetic substances. Many of these substances are recalcitrant in nature which are non-biodegradable or degrade very slowly. Such substances persist in the environment for prolonged periods of time and may, therefore, become progressively more concentrated. These recalcitrant substances are toxic, mutagenic or carcinogenic and may accumulate in the tissues of organisms. These pollutants enter the food chain through bio-magnification and ultimately affect the human beings and other living organisms.

Table 1.3 Adverse effects of pollutants of industrial wastewater

1.3 Treatment of Industrial Wastewater

The treatment of industrial wastewater is classified according to following levels (Fig. 1.2):

• Preliminary treatment

Fig. 1.2

Treatment of industrial wastewater

It is a separation process and involves the removal of debris and coarse solids.

• Primary Treatment

Primary treatment includes the removal of settleable solids (a portion of suspended solids) and part of the organic matter from the wastewater.

• Secondary Treatment

The aim of secondary treatment is the further treatment of wastewater from primary treatment to remove the residual biodegradable organic matter, suspended solids and possibly nutrients (Phosphorus and nitrogen) by means of biological process.

• Tertiary Treatment

Tertiary treatment or advanced treatment is employed for the removal of specific pollutants of wastewater which cannot be sufficiently removed in secondary treatment.

1.3.1 Wastewater Treatment Operations

The wastewater treatment methods are composed of unit operations (Fig. 1.3):

• Physical unit operations (Physical treatment)

Fig. 1.3

Wastewater treatment operations

The wastewater treatment methods in which physical forces are predominant such as screening, aeration, filtration, floating.

• Chemical unit operations (Chemical treatment)

The treatment methods in which removal of pollutant occurs by addition of chemical products or due to chemical reactions such as ozonation, coagulation, advanced oxidation processes.

• Biological unit operations (Biological treatment)

The treatment methods in which removal of pollutant occurs by means of biological activity under aerobic and anaerobic conditions such as activated sludge, trickling filtration and anaerobic digestion.

1.4 Role of Microorganisms and Plants in Biological Treatment of Industrial Wastewater

The wastewater released from various industries contains different pollutants. The discharge of untreated wastewater to natural ecosystems poses a serious threat to all life forms hence affordable and effective methods have become a necessity for the treatment of pollutants present in industrial wastewater. The conventional wastewater treatment system usually involves complicated procedures and is economically unfeasible. The biological treatment processes by means of microorganisms (bacteria, fungi, yeast, algae) and plants may present a relatively inexpensive and environment friendly way to remove different pollutants from various industrial wastewater. The use of biological system to treat the pollutants of industrial wastewater is largely dependent on source and characteristics of wastewater. Microorganisms can break down the pollutants/xenobiotics of industrial wastewater for their growth and/or energy needs. The biological systems have capabilities to remove the pollutants from wastewater by absorption, adsorption and enzymatic degradation processes. A large number of enzymes such as peroxidases, oxidoreductases, laccases, cellulolytic enzymes, proteases and amylases from a variety of different biological sources play an important role in the treatment of industrial wastewater.

1.4.1 Bacteria

The existence of diverse bacterial populations makes it possible to degrade most of the pollutant of industrial wastewater. The bacterial treatment of wastewater involves the conversion of complex organic matter to harmless simple compounds by aerobic or anaerobic process. The bacteria are frequently applied for the treatment of industrial wastewater because they are easy to cultivate, grow rapidly and suited fine for degradation and even complete mineralization of pollutants. Generally, bacteria obtain their energy from the carbonaceous organic matter (pollutant) of industrial wastewater. Some bacteria used the pollutants of industrial wastewater as their sole carbon and energy source. Several bacteria have been reported in the treatment of various industrial wastewaters (Table 1.4). These bacteria play a major role in phenol degradation, heavy metal removal (chromium reduction from leather industry), dye decolorization from textile industry, decolorization of distillery mill effluent and removal of pollutants of other industrial wastewater such as aliphatic and aromatic hydrocarbons, heavy metals, insecticides and other pollutants by biosorption or enzymatic degradation processes. Few examples of bacteria involved in treatment of pollutants of various industrial wastewaters are as follows: Aeromonas hydrophila and Bacillus sp. are capable of dye decolorization, Pseudomonas putida has potential application for bioremediation of heavy metals, Sphingomonas chlorophenolica is capable of complete mineralization of pentachlorophenol (PCP) and Pseudomonas fluorescence has capability to decolorize the distillery wastewater.

Table 1.4 List of some bacteria, fungi, algae and plants involved in biological treatment of industrial wastewater

1.4.2 Fungi

Fungi are multicellular organisms. They have lower sensitivity to variations in temperature, pH, nutrients, and aeration. Fungi have capability to treat the toxic pollutants of industrial wastewater released from various industries into harmless products by biosorption or enzymatic processes. Fungi secrete several isoenzymes which play major role in the removal of pollutants. White rot fungi such as Phanerochaete chyrosporium and Trametes versicolor are ubiquitous in nature and their adaptability to extreme conditions makes them widely exploited microorganism in treatment of industrial wastewater. They produce various enzymes including laccases, manganese peroxidases and lignin peroxidases which are involved in the degradation of various xenobiotic compounds. White rot fungi can also remove toxic metals and other pollutants by biosorption process. Their enzyme producing and biosorption activity makes them more effective in the removal of pollutants from industrial wastewater. Many fungal species are involved in the treatment of various industrial wastewaters (Table 1.4), for example, Trametes versicolor and Rhizopus oryzae has been involved in treatment of paper and pulp wastewater; Phanerochaete chyrosporium has been found effective for color removal from textile wastewater; Aspergillus fumigatus has been effective for decolorization of distillery wastewater; Fusarium oxysporum, Cadosporium cladosporioides, Gliocladium roseum, and Trichoderma koningii has been involved in removal of heavy metals from industrial wastewater.

1.4.3 Algae

Algae are a diverse group of photosynthetic organisms having potential to treat the pollutant of industrial wastewater mainly by bioaccumulation and biosorption. They are able to accumulate organic and inorganic toxic substances, heavy metals, nutrients, pesticides in their cells/bodies from the wastewater. Algae can remove the excess nitrogen and phosphorus present in industrial wastewater through absorption. Nitrogen and phosphorus are commonly present in wastewaters which are essential components for the growth of algae. A wide range of algal species including Chlamydomonas, Chlorella, Spirulina, Scenedesmus, Pediastrum, Cosmarium and Botryococcus have been utilized for treatment of various industrial wastewaters (Table 1.4). These species are used to treat and remove color, odour, nitrogen, phosphorus, heavy metals, BOD, COD and other pollutants from various industrial wastewaters.

1.4.4 Plants

Removal of pollutants with the utilization of plants is known as phytoremediation. This strategy includes the use of plants that show high survivability in contaminated sites and the capacity to uptake pollutants, which prompts consequent evacuation of pollutants. Plants have been effectively used to remove heavy metal, petroleum hydrocarbons, pesticides, organic and inorganic contaminants and industrial by-products. Plant species with phytoremediation potential should have specific properties. They accumulate, extract, transform, degrade or volatilize contaminants at the levels that are toxic to ordinary plants and furthermore they have ability to remediate various pollutants at the same time. The phytoremediation process can take place by any of the following ways like phytoextraction, phytostabilization, phytovolatization, phytodegredation, rhizofiltration. The pollutants enter the plant primarily through the roots by adsorption and accumulation. These pollutants might be stored in the roots, stems, or leaves; changed into less harmful chemicals inside the plant; or changed into gases that are released into the air as the plant transpires. There are several species of plants mainly aquatic plants known for their phytoremediation abilities to treat various industrial wastewaters such as Acorus calamus, Typha latifolia, Typha domingensis, Cynodon dactylon and Phragmites communis (Table 1.4).

1.5 Recycling and Reuse of Industrial Wastewater

There is consistently increasing demand of pure water by many industries. These industries utilize pure water and release large amount of wastewater. Due to rapid urbanization, the use of treated, partially treated and untreated wastewater in agriculture has received much attention in developing countries. In developing countries these wastewaters is utilized for irrigation purposes because wastewater is nutrient rich and provides food security. The untreated or partially treated industrial wastewater shows harmful effect on all life forms and the environment. One of the approaches to diminish the effect of water shortage and pollution is recycling and reuse of industrial wastewater. Water recycling is the reuse of treated wastewater for beneficial purposes such as agricultural and industrial processes. The wastewater can be treated by various technologies utilizing various distinctive measures relying upon the quality required. The treated wastewater has the potential to be recycled in a number of sectors such as agriculture and industries. The production of pure water (recycling) from different feed water sources is a complex procedure including a large number of steps and process units (Fig. 1.4).

Fig. 1.4

Processes of recycling of industrial wastewater

The recycling and reuse of industrial wastewater enable communities to become less dependent on groundwater and surface water sources and can diminish the redirection of water from delicate ecosystems. Also, water reuse may lessen the supplement loads from wastewater discharges into waterways, subsequently decreasing pollution. Suitable environment-friendly sanitization process is the first necessity for recycling of wastewater because they consume less energy and along these lines positively affect endeavors to alleviate the impacts of environmental change. This is critical because the environmental issues related to water usage and wastewater release cannot be tackled basically by recycling of wastewater if the recycling procedures consume large quantities of energy.