eChapters

11.1 Introduction

Generally, except particular cases, the typical civil wastewater do not present substantial differences according to the town where they are produced, therefore the type and the sequence of water treatment are nearly the same.

Conversely, the industrial wastewater characteristics are extremely varying according to the type of activity. For example, the oil industry wastewater will contain high concentrations of oily substances and hydrocarbons, the galvanic industry will produce heavy metal polluted wastewater, a food industry will produce wastewater containing biodegradable substances and so on. Consequently also the whole cycle of treatment, being aimed at the removal of particular pollutants, will be different according to kind of industry. The individual treatments of a wastewater treatment plant can be classified in different ways. According to the functioning principle it is possible to distinguish biological, physical and chemical treatments.

Biological plants are more commonly used to treat domestic or combined domestic and industrial wastewater from a municipality. They use basically the same processes that would occur naturally in the receiving water, but give them a place to happen under controlled conditions, so that the cleansing reactions are completed before the water is discharged into the environment.

Physico-chemical plants are more often used to treat industrial wastewaters directly, because they often contain pollutants which cannot be removed efficiently by microorganisms— although industries that deal with biodegradable materials, such as food processing, dairies, breweries, and even paper, plastics and petrochemicals, may use biological treatment. And biological plants generally use some physical and chemical processes, too.

10.1 Introduction

Industrial effluents, which are deteriorate their quality, and push them to the brink of extinction in the process of unplanned discharge, giving rise to the need for suitable conservation strategies for the receiving water body. Unfortunately, over the years, less attention has been given to industrial effluents world over. The degradation of the industrial effluents has altered their functions, affecting the ecological balance. The objectives of carrying out the physico-chemical and biological analyses of water bodies are as follows:

1. Generally, industrial effluent functions directly relate to their physical, chemical and biological integrity. Water quality evaluation for industrial effluent leads to information about their misuse by indicating the pollution status. 1st define water quality objectives as the overall direction and purpose of the industrial effluent and furthermore define goals as milestones to be met during the course of a book. Since the quality of aquatic life depends on the water quality, a thorough assessment of the water quality is an integral part of industrial effluent toxicity evaluation. The assessment of the chemical criteria of the industrial effluent helps in

9.1 Introduction

The sources and types of chemical pollution to which freshwater systems can be exposed are many and varied. The origins of pollutants entering these systems range from those that are predominantly point sources (i.e., industrial effluents) to those that are mainly diffuse, such as agricultural run-off and acid deposition. Some of these are effectively continuous, whereas others are intermittent or episodic.

Pollutants can also be characterized by their quality: general organic loading, specific organic toxicants, inorganic toxicants, and acids. While most of the sources listed above produce mixtures of these characteristics, particular components are enhanced. Industrial effluents generally are the source of specific toxicants, but might also lead to general organic loading.

Some consideration should also be given to the types of system exposed to these pollutants. Most freshwater systems flow, but some more rapidly than others; that is, lakes and ponds have a slow throughput, the so called lentic systems whereas that for rivers and streams is rapid. Because they flow rapidly, the so-called lotic systems have been used for the transport of materials, such as removing industrial pollutants from factories and organic effluents from sewage works.

A view exists that lotic systems that depend substantially on organic inputs from terrestrial ecosystems as a basis for their economy should have the capacity for self-cleansing of at least organic pollutants. However, this perception has been challenged recently (Royal Commission on Environmental Pollution, 1992). Of course, “still” or so-called lentic waters may also be important repositories of pollutants, and are certainly exposed to diffuse inputs from agricultural land leading to eutrophication.

Thus, the challenge for aquatic ecotoxicology is to develop methods that can not only assess but also estimate the ecological impact of chemicals on a variety of complex ecosystems under diverse and complicated circumstances (e.g., periodic perturbations or steady trickles, and mixtures of varying complexity). The predictive approach is important in risk assessment used in the regulation of chemical pollutants. Assessment, at times referred to as a “retrospective approach,” is used to determine whether particular contaminants have an impact on specified natural ecosystems. This chapter reviews current methods, first predictive and then retrospective approaches, to address such problems. Initially, one must define what is to be measured, for it has relevance to both approaches.

8.1 Introduction

Contamination of drinking water supplies from industrial waste is a result of various types of industrial processes and disposal practices. Industries that use large amounts of fresh water for processing have the potential to pollute waterways through the discharge of their waste into streams and rivers, or by run-off and seepage of stored wastes into nearby water sources. Other disposal practices, which cause water contamination, include deep well injection and improper disposal of wastes in surface impoundments.

Industrial wastes consists of both organic and inorganic substances. Organic wastes include pesticide residues, solvents and cleaning fluids, dissolved residues from fruits and vegetables, and lignin from pulp and paper to name a few. Effluents can also contain inorganic wastes such as brine salts and metals. This is an incentive for industry to pre-treat their water by neutralizing the chemically active components, recycling, dilution or extraction and collection for proper disposal.

The waste disposal practices, which presently pose a threat to drinking water supplies, include deep well injection of wastes and wastes that are dumped and retained in surface impoundments or evaporation ponds. (Ministry of Industries, 1994).

In keeping with the functions delegated to the Central Pollution Control Board under the Water (Prevention & Control of Pollution) Act, 1974, they covered a number of industries, their production and location with details of receiving water besides details on the raw material they used, the process they adopted to process them, inplant control systems, pollution control system provided and the future requirement with cost implications, monitoring system etc.

These documents are also aimed at developing standards for effluents and emissions as Minimal National Standards that can be adopted uniformly throughout the country. The State Pollution Control Boards (SPCBs) can tighten the standards, wherever the local situation demands.

While implementing these standards, the status of technologies adopted by the industries and further requirements to meet the overall objective of pollution control have been assessed. The technology requirement for pollution control industry wise has been presented in the following groups of industry categories.

7.1 Introduction

The rapid population and industrial growth experienced beginning in the middle part of this century has led to spiraling increases in the demand for forest wood. Historical data reveal that there was a 159.6% increase in overall wood production between 1970 and 1993. Wood is defined simply as wood in the rough, and includes trees felled for any purpose. The majority of total wood production has been for use as fuel wood and charcoal, much of which is harvested by villagers, and to some degree urban squatters.

Since 1970, there has been a 160% increase in fuel wood and charcoal production. The largest portion (104%) occurred between 1970 and 1980, which may be attributed to the introduction of fuel wood species earlier, during the Second Five Year Plan period. Looking at the decades to come, the demand for fuel wood is likely to continue growing in pace with future increases in population, which is growing at the rate of 24 % per decade. It is estimated that by the year 2010, demand for fuel wood and charcoal will exceed 33 million cubic meters (FAO, 1993). Since there is expected to be little further change in the area under potential productive forests, there will be an increasing probability of a shortage of wood production in India (Planning Commission, 1992).

6.1 Introduction

The state of India’s forests is important in many ways, whether it be as a source of fuel and fodder for rural citizens, of industrial inputs for a growing economy, as a habitat for thousands of plant and animal species, a sink for carbon dioxide emissions, or as a protective cover for its soils.

The forest resources forms an ecological system consisting of tree dominated vegetative associations. Forests not only provide timber, fuel wood, pulpwood fodder and fiber grasses, and non wood forest produce and support industrial and commercial activities but also maintain the ecological balance and life support systems essential for food production, health, and all round human development. The innate complexity and inherent diversity of forest ecosystems make it difficult to establish clear cause-and effect relationship or to predict the outcomes of a given intervention accurately. Figure 6.1 shows that the percentage of land mass with forest covered and non forest area in India

5.1 Introduction

The source of pollution are many and varied. The most critical are domestic sewage and industrial effluent discharging into rivers, lakes, ponds etc. Treatment facilities for domestic sewage in class 1 cities having population of more than 1,00,0000 and class 2 cities having population between 50,000 and 99,999 can process hardly 10% of the wastewater generated. Wastewater treatment facilities are difficult to quantify due to lack of continuous data. On an average, the treatment capacity in class 1 cities can handle only 60% of the wastewater collected and less than 15% of the total volume of wastewater generated.

The Indian industry has grown annually at an average rate of 5.5% during the last 50 years. Among different industrial sectors, water pollution is concentrated with in a few industrial sub-sectors mainly in the form of toxic wastes and organic pollutants. Out of the total pollution contributed by the industrial sub-sectors, 40% to 45% of the total pollutants can be traced to the processing of industrial chemicals and nearly 40% of the total organic pollution to the food products industry alone. Food products and agro-based industries together contribute 65% to 70% of the total industrial wastewater in terms of organic load. Blair T Bower, consultant, the Urban Institute, USA, remarks: "… If substantial further growth of Asia’s cities cannot be avoided and if the environmental disasters that could be associated with that growth are to be prevented, there is only one alternative: urban environmental quality management must be substantially improved throughout the region".

The total quantity of water used by the domestic and industrial sectors is much less than that consumed for irrigation. However, the wastewater released from the above sectors has a great concentration of pollutants, and is discharged at specific disposal points. Thus, the wastewater generated from domestic and industrial projects causes much more water pollution as compared to any other source.

4.1 Introduction

India is a land of many rivers, lakes, ponds, coastal, marines and mountains. Its geographical area of about 329 million hectare is crises crossed by a large number of small and medium, large rivers, some of them figuring amongst the mighty rivers of the world. The rivers and mountains have a greater significance in the history of Indian civilizations, development, religious and spiritual life. It may not be an exaggeration to say that the rivers are the heart and soul of the Indian civilizations

India is a union of States with a federal set up. Politically, the country is divided into 26 States and 7 Union Territories. A major part of India’s population of 869 millions (1991 census) is rural and agriculturally oriented for whom the rivers are the source of their life. India is a land of many religions, diversity of cultures and languages. The different regions of the country have different cultural, linguistic and other ethnic groups. The land and people present a vast panorama of diversity in unity. Physiographically, India may be divided into seven well-defined regions.

3.1 Introduction

India, when gained independence in 1947, was predominantly an agrarian economy, with a stagnant national income. The country inherited a weak industrial base, restricted to only a few industries. Agricultural growth was virtually negligible, the country had a stagnant cropped area where by only a very small proportion of agricultural land was irrigated. On the eve of the country’s independence, on 15^th August 1947, Jawaharlal Nehru, India’s Prime Minister, reminded the country that the task ahead included ending poverty, ignorance, and disease and inequality of opportunity. India began the process of planning with the launching of the 1^st five-year plan in April 1951. The central purpose of planning was to ‘initiate a process of development which would raise living standards and open out to the people new opportunities for a richer and more varied life’. Afterwards, the five-year plans were formulated seeking development in a sustainable manner.

The country, over the past has travelled a long way indeed in its drive towards economic growth, modernization of the economy, feudal economy at the time of independence has been transformed into one based on a fairly developed and diversified industrial structure and a sound agricultural base with a large potential for further industrialization and development. The income and consumption levels of people, on an average, have increased and the consumption basket has diversified. A noteworthy achievement indeed has been the elimination of famines with which the country continued to be afflicted right until independence. That achievement is far from negligible since many other countries in Asia and Africa are yet to free themselves of this malady. There is also other achievement, varying from the successful functioning of a democratic system to the emergence of a strong and large scientific community (Dreze Sen, 1995). The figure 3.1 shows the per capita income during 1997-1998. It shows that the maximum income from Northern India compared to Southern India. However, having adapted the pattern of economic development that brought prosperity to the Western, India has also seen widespread environmental damage and degradation in the pursuit of economic growth. The concern for preserving the environment against the onslaught of industrial expansion, intensification of agricultural, and adoption of a resource-intensive lifestyle has not been given the attention it deserved, and the costs of environmental degradation have not been internalized in the development process. While the Indian economy study made by two World Bank staffers shows that the country is paying an enormous price for this onward march, which has brought in its wake ecological devastation and numerous health problems.

The science is a process of refining our understanding of nature by continual questioning and active investigation on questions. Students can approach science in this manner, rather than as a collection of facts to be memorized. The Environment is to provide up-to-date information to the important concepts in the study of environment. Information is presented from an analytical, observation and multidisciplinary perspective from which we must view environmental issues in order to deal successfully with them. The environment may be defined as response of a human being influenced by various factors such as abiotic and biotic, which are present in the ecosystems.

2.1 Multidisciplinary Approach

The approach of environment science is multidisciplinary in nature like botany, zoology, physics, hydrology, hydraulics, chemistry, biophysics, biochemistry and biology. It integrates various subjects and includes few of the most important topics of modern civilization as well as oldest philosophical concerns. Applied and basic aspects of environment requires a solid function in the nature of our relationship with nature, in addition to fields like economics, anthropology, history, sociology and philosophy of the environment.

Water is an important element for life on the earth. It is an essential recurrent natural resource for environmental sustenance, agricultural productivity, industrial growth, power production, enrichment and renewal of land and air. For easy assess to the water, the first human settlements occurred along the banks of rivers and ensuing civilizations flourished in river valleys. For example, the Indian civilization of Mohanjodaro and Harappa developed in the Indus valley, the Egyptian civilization in the Nile valley, the Chinese civilization in the Yangtze valley, the Babylonian civilization between the Tigris and the Euphrates rivers, Aztec, Maya and Incas civilization in the basin of Amazon river.

The industrial revolution, which, began in the early 18th century in some European and Asian countries, set in the motion for new forces in the society and greatly changed the pattern of social life on the earth. Rapid industrialization and urbanization subsequently brought many changes in the environment and ecosystems in the world. India also witnessed a phenomenon of industrial development in the post independent era. The last four to five decades have witnessed population explosion and increase in the per capita consumption of food, consumer goods and utilization of natural resources. These have lead to the proportionate increase in the domestic and industrial effluent generation in India. The water pollution is continuously increasing at an alarming rate in Europe and Asia. By the end of this century. India's Population is projected to double itself from its present level. Similarly the per capita consumption of food has been estimated to increase by 40% resulting in 50 % production of industrial and domestic effluents in near future.

Apart from the quantity, there will be qualitative changes in the effluent generation which are likely to contain greater amount of oil, toxic chemicals, detergents and dyes. A large number of these compounds are non-biodegradable and are cumulative, thus rendering toxic product. Certain group of animals and plants are selective in their functions and can executive certain toxic chemicals and heavy metals. These biomes are helping more effectively on recycling of industrial effluent as well as domestic effluent management system.

In nature, there exists a balance between abiotic and biotic communities like animals and plants population, raw materials and total biomass present at any time. This balance ensures natural recycling and optimum production in naturally balanced ecosystems. The plant growth is slow, but it ensures optimum utilization of waste products and a healthy environment. The increased population and its human desire to possess all comforts and pleasures had lead to over exploitation of natural resources. The high demand of natural resources lead to the beginning of waste accumulation due to the creation of man made imbalances in the environment. The environment is to provide up to date information about important concepts in surrounding. Information is presented from an analytical, observational and multidisciplinary perspective from which we must view environmental issues in order to the study successfully.

Greenhouse technology development has made good progress in India during the last two decades, and steps necessary for promoting greenhouse cultivation of flower and vegetable crops have been started. Energy-efficient greenhouse cultivation continues to be an area of active research and development, and this is sought to be achieved through precision equipment and protocols. While the gap between the demand and supply of most horticultural crops remains wide and the country plans to double the production of horticultural crops by 2012, the protected cultivation technology holds the key to meet the targets. It clearly emerges that greenhouse technology has multipurpose application for sustainable development of a hilly zone. During harsh winter which otherwise threatens the survival of human beings in these remote hilly areas, popularization and further improvements in greenhouse management could provide a sign of relief in solitude of white snow cover.

The popularity of greenhouse-grown produce continues to rise as it provides a variety of produce during the “off” season. Greenhouses are good for healthy plant nursery production and other a number of crops for profit. Though the greenhouse farming in India like in other countries is progressing but there are certain problems and constraints as stated below.

1.Greenhouse production generally is highly technical and requires constant and continuous attention during cropping period. Relevant information about the crop environmental requirement such as right temperature, humidity etc is essential.

2.Knowledge about the right type of inputs for greenhouse production is a must which is not easily available.

3.Greenhouses cultivation increases the land, water and fertilizer productivity along with reduction in pesticide use. But such interventions are associated with very high initial cost. Although, it is linked with several Government Schemes in India and have 50-90% of subsidies depending on intervention, status / socio-economic condition and policy of State and Central Government.

4.Uninterrupted and regular power supply is required for operating cooling and heating system of the controlled environment greenhouses which necessitate a back-up power pack which is also expensive and underutilized.

Nutrient film technique popularly known as NFT is one of the methods of soilless farming or hydroponics where in plants have their roots in a shallow stream of recirculating water containing all the nutrients required for plant growth dissolved without any solid growing medium. The lower portion of roots remain submerged in flowing nutrient medium in a water tight gully having enough air for the roots. The nutrient film technique was developed during the late 1960s by Dr Allan Cooper at the Glasshouse Crop Research Institute, England. The method is already used in commercial horticulture in many countries including India. NFT is potential for other crops such as animal fodder and even energy-source plants for fuel production.

NFT related technologies

Hydroponics : Cultivation of plants in nutrient solutions is known as hydroponic cutlivation. This ia gerally done under protected structures and in containers arranged horizontally or vrtically (vertical garden). Use of nutrient film or fertilizers is made to feed the plants. Hydroponics can be practiced following nutrient film technique method, trough method, deep water floating method and coco peat bag culture.

Soilless media or culture

Gravel culture is a general term which applies to the growing of plants without soil in an inert medium into which nutrient solutions are usually pumped automatically at regular intervals. Haydite (shale and clay fused at high temperatures), soft- or hard-coal cinders, limestone chips, calcareous gravel, silica gravel, crushed granite and other inert and slowly decomposing materials are included in the term “gravel”. The more important greenhouse flowering crops include roses, carnations, chrysanthemums, gardenias, snapdragons, lilies, asters, pansies, annual chrysanthemums, dahlias, bachelor buttons and others.

Media ingredients and Mix

Commercially available materials like peat, sphagnum moss, vermiculite, perlite and locally available materials like sand, red soil, common manure/ compost and rice husk can be used in different proportions to grow greenhouse crops. These ingredients should be of high quality to prepare a good mix. They should be free from undesirable toxic elements like nickel, chromium, cadmium, lead etc. Most common medium other than soil used in India in greenhouses is coco peat. In other countries these are Rockwool and Peat-vermiculite.

Pasteurization: The heat treatment given to soil to free it of harmful microorganisms or pathogens and pests is called pasteurization. It kills weed seeds also.

Pasteurization of greenhouse plant growing media

Greenhouse growing medium may contain harmful pests such as disease causing organisms, nematodes, insects and weed seeds. It is advisable to decontaminate it by heat treatment or by treating with volatile permissible chemicals.

Flooding

Flooding affects both above and below ground ecosystem processes in greenhouses. Below-ground changes may be less obvious, they are as important as the above-ground changes. Soil microorganisms are sensitive to disturbance, and shifts in soil microbial community structure are expected when anaerobic conditions develop from flooding. The useful aerobic microbes are destroyed by flooding. It takes time to built-up their population in the soil to benefit plants. Due to anaerobic condition created by flooding in greenhouse plant roots in soil are not able to breath, function and hence wilting of plants occurs. Flood irrigation in excess create flood like condition in greenhouses at time. Excess water in soils is a major factor affecting plant survival and functioning. In saturated soils, the supply of atmospheric oxygen into the soil is curtailed and various facultative and obligate anaerobic microorganisms use oxidized compounds as electron acceptors for respiration, thus converting them to reduced forms. The reduction and the associated processes influence plant survival, growth and functioning in wetlands. Flood irrigation should always be just wet the soil not flood inviting stagnation of water.

A chain of reactions is initiated upon soil flooding leading to reduced soil redox potential conditions. These reactions include physical, chemical and biological processes that have significant implications on plants growth. Physical processes include restriction of atmospheric gas diffusion in the soil leading to depletion of soil oxygen and accumulation of carbon dioxide. Shortly after flooding, the limited supply of oxygen in soil pore spaces is depleted rapidly by roots, microorganisms, and soil reductants. This process leads to oxygen depletion and reduction in soil oxidation reduction potential followed by a chain of soil chemical changes. The processes that follow include denitrification, reduction of iron, manganese and sulphate, and changing soil pH

Drainage is the natural or artificial removal of excess water from a surface or sub-surface from an area or field or soil or greenhouse. The internal drainage of most agricultural soils in greenhouse is good enough to prevent severe waterlogging. Water logging creates anaerobic conditions that harm root growth in absence of oxygen. Soils need artificial drainage to improve production or to manage water supplies in certain conditions. Though the roots need moisture but they need oxygen too and poor drainage is g result in roots rotting and death of plants.

The irrigation water inside the greenhouse may accumulate and cause anaerobic condition. Similarly plants in pots should not accumulate water. Water should not stand in pots and beds for longer period. If it stays longer drainage is poor and needs to be corrected. It is better to have good drainage system in greenhouses or protected structures.

Besides irrigation rains water seeps in the greenhouse. The drainage system prevents running or its accumulation in low lying portion of the greenhouse. Drainage system in greenhouses is a must for avoiding damage to the crops.

The following various types of irrigation methods and their systems are used in crop production in greenhouses and plant nurseries.

1.Hand Watering

2.Perimeter Watering System

3.Tube Watering System

4.Drip Irrigation System

5.Overhead Spray System

6.Ebb and Flow System.

About 80% of the world population live in developing countries and are dependent on agriculture. Agricultural products, just after harvesting, are dried to the safe moisture level. Open solar drying for drying agricultural products is being practiced since ages throughout the world. Due to its several drawbacks as danger of (dust, rain, ultra-violet rays, birds, animals etc.), advance technique, i.e. greenhouse drying, is being adopted for drying crops to reduce the drying time and increase the quality of the food products.

Drying involves a heat and mass transfer phenomenon in which heat energy supplied to the product surface is utilized in two ways: (i) to increase the product surface temperature in the form of sensible heat and (ii) to vaporize the moisture present in product through the provision of the latent heat of vaporization. The removal of moisture from the interior of the product takes place due to induced vapour pressure difference between the product and surrounding medium. The moisture from the interior diffuses to the product surface to replenish the evaporated surrounding moisture.

The working principle of greenhouse drying is in which the product is placed in trays receiving the solar radiations through the plastic cover and moisture is removed by natural convection or forced convection.

Greenhouse drying are being adopted to reduce the losses and to increase the quality of the dried products. Solar energy is the most promising power source of energy for drying of agricultural products. Most of the farmers adopt open sun drying because it is abundant and inexpensive. But the open sun dried products are also subjected to remarkable losses due to environment. Losses of fruits and vegetables are estimated to be 30%-40% during drying under open sunlight. The post-harvest losses can be reduced by adopting advanced means of drying, i.e. greenhouse drying. The greenhouse dryer can be operated in natural and forced mode as required. Studies reveal that the greenhouse dried products are of superior quality and better colour retention as compared to open sun drying.