Since the onset of the Industrial Revolution, human activities have continuously generated waste. In contemporary times, due to increased patterns of production and consumption, societies are producing an unprecedented volume of waste. Although nature has a certain capacity to assimilate waste, current waste generation exceeds that capacity, leading to serious environmental degradation in the 21st century.
In the simplest terms, waste refers to any material item that has lost its utility. It includes anything discarded due to being no longer required by an individual, either for a single reason or multiple factors. Waste represents the by-products of a process that lack any further utility or function.
Typically, wastes are found in solid and liquid states and result from diverse human and animal activities. Such materials are usually deemed useless or unwanted.
Gemmell et al. (1984) described waste as “unwanted or undesirable products of life.” These can range from organic materials like human and animal excreta to chemical, metallic, and plastic by-products from industrial processes.
Bilitewski et al. (1997) proposed both subjective and objective definitions of waste:
Wastes often become problematic when their accumulation exceeds manageable limits, thus prompting environmental degradation and the need for active management interventions.
Not all waste is without value. Due to advancements in technology, many waste materials can now be reused or recycled into useful products. Often, waste for one individual might serve as a valuable resource for another.
For example:
In modern society, nearly everything can be repurposed, making the term "waste" somewhat relative.
Based on their physical state, wastes can be categorized into three major types:
These are non-soluble materials and the solid part of discarded items from different sectors. Examples include plastics, glass, food waste, paper, wood, metals, and mining residue. Most solid wastes are non-recyclable and degrade very slowly.
These include urban wastewater, sewage, industrial effluents, and agricultural runoff. They are often transported via containers or pipelines. Excessive sewage discharge into water bodies can severely disrupt aquatic ecosystems, sometimes causing fish mortality.
These are by-products in gas form resulting from various industrial and chemical activities. Common gases include methane (CH₄), carbon dioxide (CO₂), and chlorofluorocarbons (CFCs). These gases contribute to pollution, climate change, and other environmental issues.
Note: This unit will primarily focus on solid and liquid wastes.
These are produced at the household level, including waste from dwellings, apartments, and residential buildings. Common examples include leftover food, wastewater contaminated with detergent, household garbage, ashes, furniture, clothing, and plastic.
Generated from agricultural lands and associated activities, this includes organic waste from plants and animals, spoiled grains, crop residue, and chemically contaminated water from fertilizers and pesticides.
Originating from factories and manufacturing units, it comprises chemical waste, solid and liquid effluents, building material debris, and by-products from burning coal, wood, and charcoal, many of which are hazardous.
Produced during municipal activities like constructing roads, public facilities, and railways, and includes waste from household, market, commercial, institutional, and public area cleaning. It also includes treated biomedical waste.
Originates from hospitals, clinics, and laboratories, including diseased organs, blood-contaminated items, surgical waste, and experimental chemical gases.
Includes debris and remains after natural or human-made disasters such as earthquakes, landslides, floods, cyclones, and volcanic eruptions.
These are organic materials that decompose naturally, including food waste, paper, wood, textiles, and fruit and vegetable peels. They are generated across households, industries, and commercial areas. National Environmental Engineering Research Institute (NEERI), a laboratory under CSIR, conducts studies and offers environmental solutions.
In a 2004 NEERI study of 59 Indian cities, the waste generation rate ranged from 0.12 to 0.60 kg per capita per day.
According to a 2016 report by CPHEEO, biodegradable waste makes up 47.5% of India’s total municipal waste.
Comprises inorganic and recyclable materials like plastic, glass, metals, and cans. These items do not degrade easily and remain in the environment for decades or longer.
The quantity of waste is increasing daily due to the rapid growth of the population and various services aimed at improving economic well-being. This growth leads to significant waste generation, which is often not disposed of properly due to a lack of space, workforce, and inadequate waste management mechanisms in urban areas. As a result, local populations and the surrounding environment face numerous challenges due to improper waste management.
Solid waste dumped in certain areas creates a suitable environment for the growth of vermin, including mosquitoes, flies, rodents, and pigs, which are major agents of various diseases. These diseases become health concerns when they spread to local communities and surrounding areas:
Furthermore, these vermin often use solid waste areas as a source of food and shelter, exacerbating the spread of diseases. Animals like dogs, cats, and pigs also act as carriers of various diseases.
Individuals working in waste disposal sites are directly exposed to these health risks and are highly vulnerable to infections. They may encounter sharp objects like glass or metal, resulting in skin and blood infections. Animal bites and associated diseases are also common. Furthermore, exposure to dust and hazardous materials can cause chronic respiratory issues, including cancer. Chemical burns and other injuries can occur due to the improper disposal of chemicals, acids, and electronic waste. Waste from hospitals and laboratories, such as syringe needles, swabs, and bandages, is particularly hazardous and infectious, posing additional risks to workers.
The exposure to toxic chemicals in research laboratories is a major health concern for workers handling such materials.
Both solid and liquid wastes have significant adverse impacts on the environment. The improper dumping of waste in open areas and drains causes a variety of environmental problems:
The foul odors produced by the decomposition of solid and liquid wastes further affect the environment. The unpleasant smell emanating from large piles of waste and wastewater drains is unhygienic and intolerable, especially in residential areas. Waste collection centers also contribute to this issue.
The visual impact of waste disposal sites is another concern. These sites, often located along roads, highways, or residential areas, become hotspots for animals and scavengers to access food and other materials, further degrading the environment.
Solid and liquid waste management (SLWM) is crucial because improper waste handling can lead to severe environmental and public health issues. Waste management requires safety and care, as it involves several stages such as collection, transport, processing, treatment, and disposal of municipal solid and liquid waste. Effective waste management depends on the collaboration between households, communities, private enterprises, and municipal authorities. An appropriate mix of processes and technologies for waste collection, transfer, recycling, and disposal must be adopted to ensure efficiency and sustainability in the management of waste.
The most effective method for waste management begins at the source itself, where the generation of waste can be reduced. Waste generation occurs when materials are deemed no longer valuable and are discarded. Proper management of waste at the generation stage helps in reducing both economic and environmental costs. By designing, producing, packaging, and reusing products thoughtfully, waste generation can be minimized. This reduction not only cuts costs but also prevents the environmental issues related to leachate, emissions, and greenhouse gases.
Waste storage involves keeping discarded materials in designated areas until they are ready to be processed or disposed of. Different types of storage facilities, such as small containers, large containers, and shallow pits, vary in size, form, and material. Small containers are used at the household level, while larger containers cater to institutions and commercial purposes. The quantity and size of these storage facilities depend on the number of users, types of waste generated, and accessibility. These facilities must be carefully planned, ensuring that they are safe from theft or vandalism.
The collection process involves gathering waste and transporting it to a disposal site. The frequency of collection is based on the volume of waste generated. Municipal corporations are typically responsible for waste collection in urban areas, though franchised service methods may also be employed. The efficiency of the waste collection system is measured through collection efficiency, which represents the percentage of waste collected compared to the total waste generated.
Waste transportation is crucial for ensuring that waste reaches its disposal site. Various transportation methods are used depending on the volume and availability of waste. Motorized vehicles, human-driven, and animal-driven methods are employed for transporting waste. Smaller vehicles may be used to access narrow streets, while larger vehicles transport the waste to designated disposal sites. Improper waste disposal, such as dumping in non-designated areas, can lead to the clogging of drains, creating breeding grounds for rodents and insects that spread diseases.
Waste processing involves altering the physical and chemical properties of waste materials to make them reusable. This stage improves the efficiency of waste management, recovers materials for reuse, and generates energy. Common waste processing techniques include compaction, waste separation, incineration, and composting.
Processing helps to maximize the value recovered from waste materials by converting them into useful products.
Recycling and recovery are essential components of waste management, focusing on improving efficiency by recovering recyclable materials. The recycling process transforms waste into new products, reducing the need for raw materials and conserving resources. The cost-effectiveness of recovery depends on the value of the recycled materials and the market demand for these products. Materials like plastics, tin, glass, paper, and cardboard can be recovered, recycled, and reused for various purposes, contributing to a sustainable waste management system.
The final stage of solid and liquid waste management is waste disposal. Waste of every type needs to be disposed of properly to prevent harm to the local environment and the health of nearby communities.
Landfill sites are identified under the land use planning of a region and require engineering methods to minimize their impacts. The Government of India has stipulated regulations for the proper disposal of residual wastes in sanitary and lined landfills, as outlined in the Solid Waste Management Rules, 2016. These documents are available at CPHEEO website.
Advanced technological tools like Geographic Information System (GIS) software are used in monitoring waste disposal trucks, which are equipped with Global Positioning System (GPS) technology. The GPS-enabled trucks can be monitored for irregularities in waste transportation and disposal systems.