Waste Water Management
- Water, food and energy securities are emerging as increasingly important and vital issues for India and the world.
- Most of the river basins in India and elsewhere are closing or closed and experiencing moderate to severe water shortages, brought on by the simultaneous effects of agricultural growth, industrialization and urbanization.
- Current and future fresh water demand could be met by enhancing water use efficiency and demand management. Thus, wastewater/low quality water is emerging as potential source for demand management after essential treatment.
- An estimated 38354 million litres per day (MLD) sewage is generated in major cities of India, but the sewage treatment capacity is only of 11786 MLD.
- Similarly, only 60% of industrial waste water, mostly large scale industries, is treated.
- Performance of state owned sewage treatment plants, for treating municipal waste water, and common effluent treatment plants, for treating effluent from small scale industries, is also not complying with prescribed standards. Thus, effluent from the treatment plants, often, not suitable for household purpose and reuse of the waste water is mostly restricted to agricultural and industrial purposes.
- Wastewater- irrigated fields generate great employment opportunity for female and male agricultural labourers to cultivate crops, vegetables, flowers, fodders that can be sold in nearby markets or for use by their livestock.
- However, there are higher risk associated to human health and the environment on use of wastewater especially in developing countries, where rarely the wastewater is treated and large volumes of untreated wastewater are being used in agriculture.
What is wastewater?
- Wastewater or sewage is the byproduct of many uses of water. There are the household uses such as showering, dishwashing, laundry and, of course, flushing the toilet. Additionally, companies use water for many purposes including processes, products, and cleaning or rinsing of parts.
- After the water has been used, it enters the wastewater stream, and it flows to the wastewater treatment plant.
- When people visit a treatment plant for the first time, often it is not what they perceived it would be. These wastewater plants are complex facilities and provide a high quality end product.
Why treat wastewater?
- We need to remove the wastewater pollutants to protect the environment and protect public health. When water is used by our society, the water becomes contaminated with pollutants.
- If left untreated, these pollutants would negatively affect our water environment. For example, organic matter can cause oxygen depletion in lakes, rivers, and streams.
- This biological decomposition of organics could result in fish kills and/or foul odors. Waterborne diseases are also eliminated through proper wastewater treatment.
- Additionally, there are many pollutants that could exhibit toxic effects on aquatic life and the public.
How do we collect the wastewater?
- The sewer or collection system is designed so that it flows to a centralized treatment location.
- The collection system is comprised of smaller sewers with a diameter of about four inches.
- As more homes and companies are connected along the system, the pipes become larger in diameter.
- Where gravity systems are not practical, pumping stations are often included to lift the wastewater.
What is Primary Treatment?
- Primary treatment is a physical settling process that removes solids. Wastewater that enters the primary settling tank (or clarifier) is slowed down to enable the heavier solids to settle to the bottom.
- Lighter materials, such as grease, will float to the top of the tank. Settling tanks are designed with mechanisms to remove both the settled solids, as well as the floating solids. Primary clarifiers are either circular or rectangular.
- Both types work equally well when properly designed and maintained. Not all plants have primary treatment. Primary treatment generates primary sludge.
- The sludge is removed and pumped to the solids treatment process for ultimate removal.
What is Secondary Treatment?
- Secondary treatment is a biological treatment process used to stabilize the dissolved solids.
- Microorganisms (e.g., bacteria) feed on the organic solids (food) in the wastewater and convert the organics into a cellular or biological mass that can later be removed.
- These biological processes are aerobic processes. Oxygen must be provided for these aerobic organisms to work properly and efficiently. An integral part of secondary treatment processes is another set of settling tanks or clarifiers.
- These secondary clarifiers (final clarifiers) remove the biological mass that has grown during biological treatment.
What comes after Secondary Treatment?
- In many plants, the next process is called disinfection. Disinfection means the inactivation of disease-causing organisms.
- It is sometimes confused with sterilization which means the killing of all organisms.
- In disinfection, the wastewater following secondary treatment is usually treated in one of two ways: (1) chlorination or (2) ultra-violet radiation.
- Chlorination involves the use of chlorine, either in the form of a gas (less common today), or as a liquid (sodium hypochlorite).
- The chlorine oxidizes the microorganisms. The effectiveness of this process is monitored by testing the fecal coliform group.
- This indicator group of microorganisms are easy to grow in a laboratory and are tougher to kill than pathogens. Some chlorination systems also have dechlorination systems to remove any residual chlorine.
Ultraviolet (UV) disinfection systems
- Ultraviolet (UV) disinfection systems contact the treated secondary wastewater with UV light bulbs that are encased in clear housings.
- The UV light kills pathogenic organisms by using a germicidal photochemical wavelength.
- Unlike chlorination, UV leaves no residual in the wastewater with which to be concerned.
- Plants that use UV must either have dual UV systems or have chlorination as a backup. Additionally, these UV systems are energy consumptive.
What is Advanced Treatment?
- Some treatment plants may be required to remove nutrients (nitrogen and phosphorus) due to the possible negative impacts on the receiving stream (e.g., ammonia toxicity to fish).
- Advanced treatment processes are used to remove nutrients, additional solids, and/ or biochemical oxygen demand.
- Advance treatment provides a very high level of treatment that goes beyond secondary treatment.
- In the case of nitrogen removal, the processes are biological. For phosphorus removal, chemical additives are normally required.
Policy and Regulatory Framework for Wastewater
- Wastewater shares the policy and regulatory framework with water; however with some differences such as the role of bodies such as the Central Pollution Control Board (CPCB) becomes more critical.
- The CPCB, under the MoEF, is an advisory body to the government for prevention and control of water and air pollution and for improvement in air quality. At the state level, the state departments of environment and forests with the advice and assistance of the state pollution control boards (SPCBs) are responsible for enforcing the environmental acts and rules, and monitoring them.
- Meanwhile, many ad hoc expert appraisal committees (at the centre and state level) play a significant role in the grant of environmental clearances.
- Research is being conducted on applications of bio-technology on the treatment of industrial effluents – especially for paper and pulp industry, electroplating, distillery, tannery, dye and refineries – and biosensors for detection of pollutants, especially residues of pesticides and bio-diversity.
- Regulatory frameworks for on-site systems are virtually non-existent in India.
Solid Waste Management; Types of Solid waste Management; Factors affecting Solid Waste Generation
Solid Waste Management
- Solid waste management is basic public services which every citizen should have access to, both for health and hygiene, and for ensuring a good quality of living. Sanitation here refers to toilet facilities, whereas solid waste management refers to the management collection and disposal of solid waste (as opposed to liquid waste).
- The image of a city as being clean and free of waste, impacts its desirability for doing business by entrepreneurs and for future residents to live.
- Municipalities in India are responsible for collection, sweeping, storage, transfer, treatment and final disposal of waste.
- A study by NIUA (2015) reports that urban areas in India generate more than 100,000 MT of waste every day, with Mumbai contributing 7000 MT, and Bangalore, 5000 MT.
- While the Ministry of Urban Development has mandated several management and handling rules for solid waste, most cities and towns are finding it difficult to comply with these rules, keep their streets clean, and safely dispose the waste.
- An analysis of waste disposal in 22 of India’s cities by the Federation of Indian Chambers of Commerce and Industry (FICCI (2009)), as pointed by Sridhar and Kumar (2013), shows that 14 out of India’s 22 cities which were studied, sent more than 75 per cent of their waste to dumpsites, indicating a lack of adequate treatment and disposal facilities.
- Mumbai sends 100 per cent of its waste to dumpsites, while Delhi dumps 94 per cent of its waste.
Solid waste management Methods
- This method involves collection of municipal waste from all over the local area and by means of landfilling, dump outside the city/nagar panchayat limits.
- This process looks at door-to-door collection of solid waste by waste pickers who hand over to the collection team who then discard the collected waste in the landfill.
- The waste pickers are employees of the Municipal Corporation or Nagar Panchayat. The collection team is generally contracted out by a tendering process.
- This is a model seen in a few places like Suryapet in Andhra Pradesh and Bangalore in Karnataka. The waste is collected ward-wise and is segregated at source into bio-degradable and non-biodegradable.
- The biodegradable waste is composted at a nearby facility by different methods of aerobic and anerobic composting.
- The non-biodegradable waste is further categorised into paper, plastic, metal and other waste and then further collected by recyclers for up-cycling or downcycling of products
Rules and regulations associated with SWM
- Under the 74th Constitutional Amendment, Disposal and managemenf of Municipal Solid Waste is one of the 18 functional domains of the Municipal Corporations and Nagar Panchayats.
- The various rules and regulations for solid waste management are:
- The Bio-Medical Waste (Management And Handling) Rules, 1998
- Municipal Solid Waste (Management And Handling) Rules 2000
- The Plastic Waste (Management And Handling) Rules, 2011
- E-Waste (Management And Handling) Rules, 2011
- There are other court cases that find their importance in terms of Solid Waste Management in India:
- Almitra Patel vs. Union of India
- L Wadhera vs. Union of India.
- Judgement of Karnataka High Court towards Mandatory Segregation at Source
Solid Waste Management – Major Issue for India
- The Government of India had notified the Municipal Solid Waste (Management and Handling) Rules in 2000, thereby making it mandatory for all urban local bodies in the country to engage in collection, segregation, secondary storage in covered bins, transportation in covered vehicles, processing through composting or waste-to-energy technologies and disposal of rejects in engineered/sanitary landfills.
- Door to door collection coverage is scanty at best, and segregation at household level is a rarity.
- Collection even from community bins is not regular. Collection efficiency is low.
- Processing is limited to very small portion of the waste.
- Dumping is done in land-fills without any regard for environment and without following scientific methods of disposal. Such inadequate disposal practice lead to problems that will impair human and animal health and result in economic, environmental and biological losses.
- Improper waste management causes public health and environmental hazards like climate change, air and water pollution, soil contamination, spreads odours and disease, and breeds vermin including flies, mosquitoes, rats, dogs and monkeys.
- Even after 12 years, most cities have confined themselves to collection and transportation of solid waste. Processing and safe disposal are being attempted only in a few cases.
- The CPCB report also reveals that only 68% of the MSW generated in the country is collected of which, 28% is treated by the municipal authorities. Thus, merely 19% of the total waste generated is currently treated. .
Some of the major issues concerning solid waste management are:
- Absence of segregation of waste at source
- Lack of funds for waste management at ULBs
- Lack of technical expertise and appropriate institutional arrangement
- Unwillingness of ULBs to introduce proper collection, segregation, transportation and treatment/ disposal systems
- Indifference of citizens towards waste management due to lack of awareness
- Lack of community participation towards waste management and hygienic conditions
- Lack of sewage management plan.
Suggestion Made by Kasturirangan report For Solutions of Solid Waste
The Kasturirangan report by PC highlights the need for an integrated approach:
- Reduction and segregation of waste at source and also efficient utilization of various components of the waste.
- Principle of Reduce, Reuse, Recover , Recycle and Remanufacture (5Rs) should be adopted
- Motivate Resident Welfare Associations (RWA), CBO / NGO’s to take up work of community awareness and door to door collection
- Integration of kabadiwalas and rag pickers into MSWM system
- It emphasizes setting up centralised (for incineration, gasification, pyrolysis) or decentralised (for biomethanation, vermicomposting) waste processing facilities keeping in view the quantity and quality of waste generated and financial viability of the processing technology.
- Set up Common Regional Sanitary Landfill Facility, to reduce the land requirement. Cities above a population of one million should set-up their own landfill and permit all cities and towns within 50km periphery of the city to use the facility for disposal of their waste.
Internationally good example for Solid Waste Management:
- For instance, Copenhagen recycles most of the waste it generates and lets only 3 per cent go to the landfill.
- Japan: In Japan, Incineration has been the primary disposal route for waste due to lack of space for landfills – 74% of all waste produced in Japan is incinerated with just 2% sent to landfill.
- Extending the idea of recycling, Kitgum town in Uganda traps used water from houses and utilises it to grow food in grey water gardens.
Different type of Waste
Municipal Solid Waste
- Municipal solid waste (MSW) is generated from households, offices, hotels, shops, schools and other institutions.
- The major components are food waste, paper, plastic, rags, metal and glass, although demolition and construction debris is often included in collected waste, as are small quantities of hazardous waste, such as electric light bulbs, batteries, automotive parts and discarded medicines and chemicals.
Industrial Solid Waste
- Industrial solid waste in Indian states, as elsewhere, encompasses a wide range of materials of varying environmental toxicity.
- Typically this range would include paper, packaging materials, waste from food processing, oils, solvents, resins, paints and sludges, glass, ceramics, stones, metals, plastics, rubber, leather, wood, cloth, straw, abrasives, etc.
- As with municipal solid waste, the absence of a regularly up-dated and systematic database on industrial solid waste ensures that the exact rates of generation are largely unknown
Agricultural Waste and Residues
- Expanding agricultural production has naturally resulted in increased quantities of livestock waste, agricultural crop residues and agro-industrial by-products.
- With rapid development in agriculture, industry, commerce, hospital and health-care facilities, the Indian State is consuming significant quantities of toxic chemicals and producing a large amount of hazardous waste.
- Currently, there are about 110000 types of toxic chemicals commercially available.
- Each year, another 1 000 new chemicals are added to the market for industrial and other uses.
- The availability of robust data on the generation of hazardous waste for Indian States is limited by the reliability of information on the quantities and types of hazardous waste produced at the country level.
- This is due to a variety of reasons, including the lack of qualified personnel to undertake the necessary assessment, the reluctance of industries to provide process information (including waste arising data) and a poor appreciation of the extent to which generated waste is hazardous.
- Where data is available, significant difficulties are encountered in seeking to draw international comparisons due to differences in classification and definition of hazardous waste from country to country within in the region.
- Most hazardous waste is the by-product of a broad spectrum of industrial, agricultural and manufacturing processes, nuclear establishments, hospitals and health-care facilities.
- Primarily, high-volume generators of industrial hazardous waste are the chemical, petrochemical, petroleum, metals, wood treatment, pulp and paper, leather, textiles and energy production plants (coal-fired and nuclear power plants and petroleum production plants).
- Small- and medium-sized industries that generate hazardous waste include auto and equipment repair shops, electroplating and metal finishing shops, textile factories, hospital and health-care centres, dry cleaners and pesticide users.
Type-based classification Solid Waste
Classification of wastes based on types, i.e., physical, chemical, and biological characteristics of wastes, is as follows:
- This refers to animal and vegetable wastes resulting from the handling, sale, and storage, preparation, cooking and serving of food.
- Garbage comprising these wastes contains putrescible (rotting) organic matter, which produces an obnoxious odour and attracts rats and other vermin.
- It, therefore, requires special attention in storage, handling and disposal.
- Ashes and residues:
- These are substances remaining from the burning of wood, coal, charcoal, coke and other combustible materials for cooking and heating in houses, institutions and small industrial establishments.
- When produced in large quantities, as in power-generation plants and factories, these are classified as industrial wastes.
- Ashes consist of fine powdery residue, cinders and clinker often mixed with small pieces of metal and glass. Since ashes and residues are almost entirely inorganic, they are valuable in landfills.
- Bulky wastes:
- These include large household appliances such as refrigerators, washing machines, furniture, crates, vehicle parts, tyres, wood, trees and branches.
- Since these household wastes cannot be accommodated in normal storage containers, they require a special collection mechanism.
- Street wastes:
- These refer to wastes that are collected from streets, walkways, alleys, parks and vacant plots, and include paper, cardboard, plastics, dirt, leaves and other vegetable matter.
- Littering in public places is indeed a widespread and acute problem in many countries including India, and a solid waste management system must address this menace appropriately.
- Biodegradable and non-biodegradable wastes:
- Biodegradable wastes mainly refer to substances consisting of organic matter such as leftover food, vegetable and fruit peels, paper, textile, wood, etc., generated from various household and industrial activities.
- Because of the action of micro-organisms, these wastes are degraded from complex to simpler compounds.
- Non-biodegradable wastes consist of inorganic and recyclable materials such as plastic, glass, cans, metals, etc
- Dead animals:
- With regard to municipal wastes, dead animals are those that die naturally or are accidentally killed on the road.
- Note that this category does not include carcasses and animal parts from slaughter-houses, which are regarded as industrial wastes.
- Dead animals are divided into two groups – large and small. Among the large animals are horses, cows, goats, sheep, pigs, etc., and among the small ones are dogs, cats, rabbits, rats, etc.
- The reason for this differentiation is that large animals require special equipment for lifting and handling when they are removed.
- If not collected promptly, dead animals pose a threat to public health since they attract flies and other vermin as they decay. Their presence in public places is particularly offensive from the aesthetic point of view as well.
- Construction and demolition wastes:
- These are wastes generated as a result of construction, refurbishment, repair and demolition of houses, commercial buildings and other structures.
- They consist mainly of earth, stones, concrete, bricks, lumber, roofing and plumbing materials, heating systems and electrical wires and parts of the general municipal waste stream.
- Farm wastes:
- These wastes result from diverse agricultural activities such as planting, harvesting, production of milk, rearing of animals for slaughter and the operation of feedlots.
- In many areas, the disposal of animal waste has become a critical problem, especially from feedlots, poultry farms and dairies.
- Hazardous wastes:
- Hazardous wastes are those defined as wastes of industrial, institutional or consumer origin that are potentially dangerous either immediately or over a period of time to human beings and the environment.
- This is due to their physical, chemical and biological or radioactive characteristics like ignitability, corrosivity, reactivity and toxicity.
- Note that in some cases, the active agents may be liquid or gaseous hazardous wastes.
- These are, nevertheless, classified as solid wastes as they are confined in solid containers.
- Typical examples of hazardous wastes are empty containers of solvents, paints and pesticides, which are frequently mixed with municipal wastes and become part of the urban waste stream.
- Certain hazardous wastes may cause explosions in incinerators and fires at landfill sites. Others such as pathological wastes from hospitals and radioactive wastes also require special handling.
- Effective management practices should ensure that hazardous wastes are stored, collected, transported and disposed of separately, preferably after suitable treatment to render them harmless.
- Sewage wastes:
- The solid by-products of sewage treatment are classified as sewage wastes.
- They are mostly organic and derived from the treatment of organic sludge separated from both raw and treated sewages.
- The inorganic fraction of raw sewage such as grit and eggshells is separated at the preliminary stage of treatment, as it may entrain putrescible organic matter with pathogens and must be buried without delay.
- The bulk of treated, dewatered sludge is useful as a soil conditioner but is invariably uneconomical.
- Solid sludge, therefore, enters the stream of municipal wastes, unless special arrangements are made for its disposal.
SOLID WASTE TREATMENT
- Current treatment strategies are directed towards reducing the amount of solid waste that needs to be landfilled, as well as recovering and utilizing the materials present in the discarded wastes as a resource to the largest possible extent.
- Different methods are used for treatment of solid waste and the choice of proper method depends upon refuse characteristics, land area available and disposal cost they are as follows
- It is a controlled combustion process for burning solid wastes in presence of excess air (oxygen) at high temperature of about 1000 Degree Centigrade and above to produce gases and residue containing non-combustible material.
- One of the most attractive features of the incineration process is that it can be used to reduce the original volume of combustible MSW by 80– 90%.
- The waste is compacted or compressed. It also breaks up large or fragile items of waste.
- This process is conspicuous in the feed at the back end of many garbage collection vehicles deposit refuse at bottom of slope for best compaction and control of blowing litter.
- Pyrolysis is defined as thermal degradation of waste in the absence of air to produce char, pyrolysis oil and syngas, e.g. the conversion of wood to charcoal also it is defined as destructive distillation of waste in the absence of oxygen.
- External source of heat is employed in this process. Because most organic substances are thermally unstable they can upon heating in an oxygen-free atmosphere be split through a combination of thermal cracking and condensation reactions into gaseous, liquid and solid fraction
- Gasification is a process in which partial combustion of MSW is carried out in the presence of oxygen, but in lesser amount than that is required for complete combustion, to generate a combustible gas (fuel gas) rich in carbon monoxide and hydrogen e.g. the conversion of coal into town gas.
- When a gasifier is operated at atmospheric pressure with air as the oxidant, the end products of the gasification process are a low-energy gas typically containing (by volume) 20% CO, 15% H2, 10% CO2 and 2% CH4.
- Composting is the most responsible technical solution for many developing countries especially, where the climate is arid and the soil is in serious need of organic supplements.
- The composting process usually follows 2 basic steps, which may be preceded or followed by pre- or post treatments (crushing, sorting, humidification, mixing with other waste, etc…)
- Landfills:- Landfilling is the most simple and economical measure as far as natural decomposition occurs at the disposal site Unscientific and ordinary Landfilling is the common practice for solid waste disposal in many developing countries.
- Sanitary Landfills:- Sanitary Landfilling is a process of dumping of MSW in a scientifically designed area spreading waste in thin layers, compacting to the smallest practicable volume and covering with soil on daily basis. The methane (rich biogas) is produced due to anaerobic decomposition of organic matters in solid waste.
- Underground injection wells:- waste are injected under pressure into a steel and concrete-encased shafts placed deep in the earth.
- Waste piles:- it is accumulations of insoluble solid, non flowing hazard waste. Piles serves as temporary or final disposal
- Land treatment:- it is a process by which solid waste, such as sludge from wastes is applied onto or incorporated into the soil surface
Factors affecting the generation rate of solid waste
Factors that influence the quantity of municipal wastes generated include:
- Geographic location.
- Season of the year.
- Collection frequency.
- Use of kitchen waste grinders.
- Characteristics of populace.
- Extent of salvaging and recycling.
- Public attitudes.
Typical commercial and industrial unit waste generation rates are:
- Office buildings-0.5-1.1 kg/ employee *day
- Restaurants- 0.2-0.8 kg/customer*day
- Canned and frozen foods-0.04-0.06 tonnes/ tonne of raw product.
- Printing and publishing-0.08-0.10 tonnes/ tonne of raw paper
- Automotive-0.06-0.8 tonnes/ vehicle produced
- Petroleum refining- Tonnes/ employee*day
- Rubber 0.01-0.3 tonnes/ tonne of raw rubber.
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