Types of wastes - Industrial wastes, Agricultural wastes, Domestic wastes and e wastes: Characteristics and Environmental Impact

Industrial wastes

1.   Industrial waste is a type of waste produced by industrial activity, such as that of factories, mills and mines. It has existed since the outset of the industrial revolution. Major industries that are producing waste are leather industries,

Sugar and distilleries industries, Paper industries and textile mill

2.    Most industrial waste is neither hazardous nor toxic, but the quantity produced is large. It has serious environmental impact such as   such as air pollution, water pollution and soil pollution eg. Pressmud from sugar industry, spent wash and yeast sludge  from distillery industry, paper sludge, fly ah  from paper industry etc.,

3.    Types of industrial waste : slag, fly ash and sludge.

Slag is a partially vitreous by-product of smelting ore to separate the metal fraction from the unwanted fraction. It can usually be considered to be a mixture of metal oxides and silicon dioxide. However, slags can contain metalsulfides and metal atoms in the elemental form. While slags are generally used as a waste removal mechanism in metal smelting, they can also serve other purposes, such as assisting in the temperature control of the smelting; and also minimizing any re-oxidation of the final liquid metal product before the molten metal is removed from the furnace and used to make solid metal.

Fly ash is one of the residues generated incombustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal. Fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys of coal-fired power plants, and together with bottom ashremoved from the bottom of the furnace is in this case jointly known as coal ash. Depending upon the source and makeup of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO₂) (both amorphous andcrystalline) and calcium oxide (CaO), both being endemic ingredients in many coal-bearing rock strata.

Toxic constituents depend upon the specificcoal bed makeup, but may include one or more of the following elements or substances in quantities from trace amounts to several percent: arsenic, beryllium,boron, cadmium, chromium, chromium VI,cobalt, lead, manganese, mercury,molybdenum, selenium, strontium, thallium, and vanadium, along with dioxins and PAH compounds.

In the past, fly ash was generally released into the atmosphere, but pollution control equipment mandated in recent decades now require that it be captured prior to release. In the US, fly ash is generally stored at coal power plants or placed in landfills. About 43 percent is recycled, often used to supplement Portland cement in concrete production. Some have expressed health concerns about this.

In some cases, such as the burning of solid waste to create electricity ("resource recovery" facilities a.k.a. waste-to-energy facilities), the fly ash may contain higher levels of contaminants than the bottom ash and mixing the fly and bottom ash together brings the proportional levels of contaminants within the range to qualify as nonhazardous waste in a given state, whereas, unmixed, the fly ash would be within the range to qualify as hazardous waste.

Sludge refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes. It can also refer to the settled suspension obtained from conventional drinking water treatment,^[1] and numerous other industrial processes. The term is also sometimes used as a generic term for solids separated from suspension in a liquid; this 'soupy' material usually contains significant quantities of 'interstitial' water (between the solid particles).

When fresh sewage or wastewater is added to asettling tank, approximately 50% of the suspended solid matter will settle out in an hour and a half. This collection of solids is known as raw sludge or primary solids and is said to be "fresh" before anaerobic processes become active. The sludge will become putrescent in a short time once anaerobic bacteria take over, and must be removed from the sedimentation tank before this happens.

This is accomplished in one of two ways. In anImhoff tank, fresh sludge is passed through a slot to the lower story or digestion chamber where it is decomposed by anaerobic bacteria, resulting in liquefaction and reduced volume of the sludge. After digesting for an extended period, the result is called "digested" sludge and may be disposed of by drying and then landfilling. More commonly with domestic sewage, the fresh sludge is continuously extracted from the tank mechanically and passed to separate sludge digestion tanks that operate at higher temperatures than the lower story of the Imhoff tank and, as a result, digest much more rapidly and efficiently.

Excess solids from biological processes such as activated sludge may still be referred to as "sludge", but "biosolids" is a public relations term used to refer to treated human waste. Industrial wastewater solids are also referred to as sludge, whether generated from biological or physical-chemical processes. Surface water plants also generate sludge made up of solids removed from the raw water

Environmental impact

1.   Accumulation of heavy metals

a.    Chromium accumulation due to tannery effluent

b.   Pb, Cr, Cd,Hg due to waste paper based industrial sludge

2.   Loss of soil fertility

Accumulation of sodium chlorides due to paper pulp based industry

3.   Pollution of surface and ground water

4.   Distilleries are one of the 17 most polluting industries listed by the Central Pollution Control Board. Uttar Pradesh and Maharashtra have the highest installed capacity constituting more than 40% of the total installed capacity, followed by Madhya Pradesh (14.2%) and Tamil Nadu (9.7%). For every litre of alcohol produced, molasses based distilleries generate 8-15 l of waste water characterized by high BOD and high COD. The effluent causes apprehension of environmental pollution owing to its very high organic content. Many a times this wastewater is discharged in the water bodies either untreated or partially treated, resulting in depletion of oxygen causing wide spread mortality of aquatic organisms. As the effluent contains considerable amount of organic matter and plant nutrients, particularly potassium and sulphur, this can be applied to arable land as irrigation water and as an amendment. When applied to crops it may act as a source of plant nutrients (N, K, P, Ca, S, Cu, Mn and Zn) and has been reported to increase the yield of the crops.

5.   An average 200 litres of water is required to produce 1 kg of textile. The sources of aquatic toxicity from textile and dye industry can include salt, surfactants, ionic metals and their metal complexes, toxic organic chemicals, biocides and toxic anions. Most textile dyes have low aquatic toxicity. On the other hand, surfactants and related compounds, such as detergents, emulsifiers and dispersants are used in almost each textile process and can be an important contributor to effluent aquatic toxicity, BOD and foaming

6.   The primary residual wastes generated from the textile industry are non-hazardous. These include scraps of fabric and yarn, off-specification yarn and fabric and packaging waste. There are also wastes associated with the storage and production of yarns and textiles, such as chemical storage drums, cardboard reels for storing fabric and cones used to hold yarns for dyeing and knitting. Cutting room waste generates a high volume of fabric scraps, which can often be reduced by increasing fabric utilization efficiency in cutting and sewing.

7.   Suspended solids can clog fish gills, either killing them or reducing their growth rate. Other important impact, they also reduce light penetration. This reduces the ability of algae to produce food and oxygen

8.   The other parameter, sulphates (SO4=) can be naturally occurring or as a result of municipal or industrial discharges. Point sources include sewage treatment plants and industrial discharges such as tanneries, pulp mills and textile mills. Sulphates are not considered toxic to plants or animals at normal concentrations. In humans, small concentrations cause a temporary laxative effect. However, doses of several thousand units cause all long-term illness effects. Sulphates are toxic at very high concentrations. Problems caused by sulphates are most frequently related to their ability to form strong acids which changes the pH. In this way, phosphates are not toxic to human beings or animals unless they are present at very high levels. Digestive problems could occur from extremely high levels of phosphate

9.   The major industry in Coimbatore, Erode, Tiruppur and Karur districts of Tamil Nadu are the textile industries.

10.                On an average more than one kilolitre of water is required to produce one tone of paper, releasing 100 million kg of toxic pollutants including nutrients, sodium,   dissolved organic matter every year. Nutrients such as nitrogen and phosphorus can cause or exacerbate eutrophication of fresh water bodies such as lakes and rivers. Organic matter dissolved in fresh water, measured by Biological Oxygen Demand (BOD), changes ecological characteristics, and in worse case scenarios leads to death of all higher living organisms. Waste water may also be polluted with organochlorine compounds.

11.                Loss of biodiversity

a.    sugar may be responsible for more biodiversity loss than any other crop, due to its destruction of habitat to make way for plantations, its intensive use of water for irrigation, its heavy use of agricultural chemicals, and the polluted wastewater that is routinely discharged in the sugar production process. Eg. is the Great Barrier Reef off the coast of Australia

12.                Diseases spread

13.                Air pollution

a.    air pollution due to the transformation process of leather (hydrogen sulfide during dehairing and ammonia during deliming, solvent vapors) due to tannery industry

b.   Conventional bleaching of pulps  using elemental chlorine produces and releases into the environment large amounts of chlorinated organic compounds, including chlorinated dioxins. Dioxins are recognized as a persistent environmental pollutant, regulated internationally by the Stockholm Convention on Persistent Organic Pollutants.

c.    Nitrogen dioxide (NO₂) sulfur dioxide (SO₂) and carbon dioxide (CO₂) are all emitted during paper manufacturing. Nitrogen dioxide and sulfur dioxide are major contributors of acid rain, where as CO₂ is a greenhouse gas responsible for climate change

14.                Sulfur-based compounds are used in both the kraft process and the sulfite process for making wood pulp. Sulfur is generally recovered, with the exception of ammonia-based sulfite processes, but some is released as sulfur dioxide during combustion of black liquor, a byproduct of the kraft process, or "red liquor" from the sulfite process. Sulfur dioxide is of particular concern because it is water soluble and is a major cause of acid rain in Canada  in 2006.

Agricultural Waste characteristics and environmental impact

Agricultural waste include animal manures, crop residues.

1.   Climate change and global warming

a.    Burning of agricultural residues

b.   Emission of ammonia from poultry manure

2.   Soil salinity and water logging

3.   Alteration in the biology of rivers and lakes

4.   Contamination of ground water with nitrates

5.   Desertification/loss of biodiversity

a.    Affects soil organisms

b.   Immobilization of nutrients

Electronic waste

Waste Electronic waste, e-waste, e-scrap, or Waste Electrical and Electronic Equipment (WEEE) describes discarded electrical or electronic devices. There is a lack of consensus as to whether the term should apply to resale, reuse, and refurbishing industries, or only to product that cannot be used for its intended purpose. Informal processing of electronic waste in developing countries may cause serious health and pollution problems, though these countries are also most likely to reuse and repair electronics. Some electronic scrap components, such as CRTs, may contain contaminants such as lead, cadmium, beryllium, or brominated flame retardants. Even in developed countries recycling and disposal of e-waste may involve significant risk to workers and communities and great care must be taken to avoid unsafe exposure in recycling operations and leaching of material such as heavy metals from landfills and incinerator ashes.

Environmental effect

Electronic waste substances

Substances found in large quantities include epoxy resins, fiberglass, PCBs, PVC (polyvinyl chlorides),thermosetting plastics, lead, tin, copper, silicon,beryllium, carbon, iron and aluminium.

Elements found in small amounts include cadmium, mercury and thallium.

Almost all electronics contain lead and tin (as solder) and copper (as wire and printed circuit board tracks), though the use of lead-free solder is now spreading rapidly. The following are ordinary applications:

§  Americium: the radioactive source in smoke alarms. It is known to be carcinogenic.

§  Mercury: found in fluorescent tubes (numerous applications), tilt switches (mechanical doorbells, thermostats),^[42] and flat screen monitors. Health effects include sensory impairment, dermatitis, memory loss, and muscle weakness. Environmental effects in animals include death, reduced fertility, slower growth and development.

§  Sulphur: found in lead-acid batteries. Health effects include liver damage, kidney damage, heart damage, eye and throat irritation. When released in to the environment, it can createsulphuric acid.

§  BFRs: Used as flame retardants in plastics in most electronics. Includes PBBs, PBDE,DecaBDE, OctaBDE, PentaBDE. Health effects include impaired development of the nervous system, thyroid problems, liver problems. Environmental effects: similar effects as in animals as humans. PBBs were banned from 1973-1977 on. PCBs were banned during the 1980s.

§  Cadmium: Found in light-sensitive resistors, corrosion-resistant alloys for marine and aviation environments, and nickel-cadmium batteries. The most common form of cadmium is found in Nickel-cadmium rechargeable batteries. These batteries tend to contain between 6-18% cadmium. The sale of Nickel-Cadmium batteries has been banned in the European Union except for medical use. When not properly recycled it can leach into the soil, harming microorganisms and disrupting the soil ecosystem. Exposure is caused by proximity to hazardous waste sites and factories and workers in the metal refining industry. The inhalation of cadmium can cause severe damage to the lungs and is also known to cause kidney damage.

§  Lead: solder, CRT monitor glass, lead-acid batteries, some formulations of PVC.^[44] A typical 15-inch cathode ray tube may contain 1.5 pounds of lead,^[2] but other CRTs have been estimated as having up to 8 pounds of lead.^[20]

§  Beryllium oxide: filler in some thermal interface materials such as thermal grease used onheatsinks for CPUs and power transistors,^[45] magnetrons, X-ray-transparent ceramic windows, heat transfer fins in vacuum tubes, and gas lasers.

Domestic waste

Domestic waste/ Municipal solid waste (MSW), commonly known as trash or garbage (US), refuse or rubbish (UK) is a waste type consisting of everyday items that are discarded by the public.

The composition of municipal waste varies greatly from country to country and changes significantly with time.

In countries which have a developed recycling culture, the waste stream consists mainly of intractable wastes such as plastic film, and un-recyclable packaging. At the start of the 20th century, the majority of domestic waste in the UK consisted of coal ash from open fires

In developed countries without significant recycling it predominantly includes food wastes, yard wastes, containers and product packaging, and other miscellaneousness wastes from residential, commercial, institutional, and industrial sources. Most definitions of municipal solid waste do not include industrial wastes, agricultural wastes, medical waste, radioactive waste or sewage sludge. Waste collection is performed by the municipality within a given area. The term residual waste relates to waste left from household sources containing materials that have not been separated out or sent for reprocessing. Waste can be classified in several ways but the following list represents a typical classification.

§  Biodegradable waste: food and kitchen waste, green waste, paper (can also be recycled).

§  Recyclable material: paper, glass, bottles, cans, metals, certain plastics, fabrics,clothes, batteries etc.

§  Inert waste: construction and demolition waste, dirt, rocks, debris.

§  Electrical and electronic waste (WEEE) - electrical appliances, TVs, , computers, screens, etc.

§  Composite wastes: waste clothing, Tetra Packs, waste plastics such as toys.

§  Hazardous waste including most paints, chemicals, light bulbs, fluorescent tubes, spray cans, fertilizer and containers

§  Toxic waste including pesticide, herbicides, fungicides

§  Medical waste.

 

Environmental impact

1.   Land filling

Today, the disposal of wastes by land filling or land spreading is the ultimate fate of all solid wastes, whether they are residential wastes collected and transported directly to a landfill site, residual materials from materials recovery facilities (MRFs), residue from the combustion of solid waste, compost, or other substances from various solid waste processing facilities. A modern sanitary landfill is not a dump; it is an engineered facility used for disposing of solid wastes on land without creating nuisances or hazards to public health or safety, such as the breeding of insects and the contamination of ground water.

For some, the environmental impact of the waste disposal unit is a better alternative to filling already saturated landfills with food waste that releases methane gas and adds to global warming. Large food particles are filtered from the water system and are sent to the landfill as well, which means the less efficient and powerful the garbage disposal, the more impact it has on the environment

Energy generation

Municipal solid waste can be used to generate energy. Several technologies have been developed that make the processing of MSW for energy generation cleaner and more economical than ever before, including landfill gas capture, combustion, pyrolysis, gasification, and plasma arc gasification.^[5] While older waste incineration plants emitted high levels of pollutants, recent regulatory changes and new technologies have significantly reduced this concern. United States Environmental Protection Agency (EPA) regulations in 1995 and 2000 under the Clean Air Acthave succeeded in reducing emissions of dioxins from waste-to-energy facilities by more than 99 percent below 1990 levels, while mercury emissions have been by over 90 percent.^[6] The EPA noted these improvements in 2003, citing waste-to-energy as a power source “with less environmental impact than almost any other source of electricity

Disease spread

Food-borne bacteria can cause severe and deadly illnesses. Although municipal water is treated for over 90 different contaminants, there are a number of toxins, chemicals and bacteria that float freely in the water systems. Adding food particles potentially carrying dangerous bacteria can corrupt a system and poison ground water supplies

Household hazardous waste (HHW)

Household hazardous waste (HHW), sometimes called retail hazardous waste, is post-consumer waste which qualifies as hazardous waste when discarded. It includes household chemicals and other substances for which the owner no longer has a use, such as consumer products sold for home care, personal care, automotive care, pest control and other purposes. These products exhibit many of the same dangerous characteristics as fully regulatedhazardous waste due to their potential for reactivity, ignitability, corrosivity, toxicity, orpersistence. Examples include drain cleaners, oil paint, motor oil, antifreeze, fuel, poisons,pesticides, herbicides and rodenticides, fluorescent lamps, lamp ballasts, smoke detectors, medical waste, some types of cleaning chemicals, and consumer electronics (such as televisions, computers, and cell phones).