Solid wastes - sources - sludge from industry and farm wastes –Characteristics - Environmental problems

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Solid wastes - sources - sludge from industry and farm wastes –Characteristics - Environmental problems

Solid wastes-Sources

1. Residential sources

Garbage from residential places include food wastes, plastics, paper, glass, leather, cardboard, metals, yard wastes, ashes and special wastes like bulky household items (electronics, tires, batteries, old mattresses and used oil). Most homes have garbage bins where they can throw away their solid wastes in and later the bin is emptied by a garbage collecting firm or person for treatment.

2. Industrial sources

Industrial waste is waste produced by industrial activity, such as that of factories, mills and mines. Major industries that are producing waste are leather industries, Sugar and distilleries industries, Paper industries and textile mill. Most industrial waste is neither hazardous nor toxic, but the quantity produced is large. It has serious environmental impact as  of 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. Commercial

Commercial facilities and buildings are yet another source of solid waste today. Commercial buildings and facilities in this case refer to hotels, markets, restaurants, go downs, stores and office buildings. Some of the solid wastes generated from these places include plastics, food wastes, metals, paper, glass, wood, cardboard materials, special wastes and other hazardous wastes.

4. Institutional

The institutional centers like schools, colleges, prisons, military barracks and other government centers also produce solid waste. Some of the common solid wastes obtained from these places include glass, rubber waste, plastics, food wastes, wood, paper, metals, cardboard materials, electronics as well as various hazardous wastes.

5. Construction demolition areas

Construction sites and demolition sites also contribute to the solid waste problem. Construction sites include new construction sites for buildings and roads, road repair sites, building renovation sites and building demolition sites. Some of the solid wastes produced in these places include steel materials, concrete, wood, plastics, rubber, copper wires, dirt and glass.

6. Municipal services

The urban centers also contribute immensely to the solid waste crisis in most countries today. Some of the solid waste brought about by the municipal services include, street cleaning, wastes from parks and beaches, wastewater treatment plants, landscaping wastes and wastes from recreational areas including sludge

7. Treatment plants and sites

Heavy and light manufacturing plants also produce solid waste. They include refineries, power plants, processing plants, mineral extraction plants and chemicals plants. Among the wastes produced by these plants include, industrial process wastes, unwanted specification products, plastics, metal parts just to mention but a few.

8. Agricultural

Crop farms, orchards, dairies, vineyards and feedlots are also sources of solid wastes. Agricultural wastes also include spoiled food, pesticide containers and other hazardous materials.

9. Biomedical

This refers to hospitals and biomedical equipment and chemical manufacturing firms. In hospitals there are different types of solid wastes produced. Some of these solid wastes include syringes, bandages, used gloves, drugs, paper, plastics, food wastes and chemicals. All these require proper disposal or else they will cause a huge problem to the environment and the people in these facilities.

Sludge from industries

Sludge refers to the residual, semi-solid material left from industrial  wastewater, or sewage treatment processes. 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.

In Tamil Nadu alone, the ETPs generate about 100 tonnes of tannery sludge per day (dry basis). As the sludge contains relatively higher concentration of chromium, it is classified as hazardous material. Tannery industrial sludge is alkaline in nature (pH 7.5 to 10). Tannery industrial sludge are rich in N, especially organic N, but very poor in P. Tannery sludge contain sulfide, which impart high antibacterial activity along with chromium and organic compounds.

The average concentrations of Cr in the tannery sludge is 10,000 mg/kg followed by Na (6070 mg/kg). In addition to Cr and Na other heavy metals like Zn, Cu, Mg, Cd, Pb and As are also present. In general the metal ions present in the sludge followed the order of Cr > Na > Ca > Mg >Cu >Zn> Pb > As > Cd.

Environmental effect by tannery waste was that the most environmental effect was bad smell to the surrounding area and the secondly scarcity of fresh water. About 40 heavy metal and acid are used in the processing of raw hides. Due to lack of proper management facilities the tannery waste create environmental pollution day by day. Pollution of environment is one of the most horrible ecological crisis to which we are subjected today. About 95% of the tannery industries have been built in unplanned way at the congested places during the last fifty years. These unplanned tanneries caused environmental pollution very much. It was showed that the most harmful environmental effect was bad smell to the surrounding areas which caused environmental pollution. It caused skin diseases by spreading of waste in water and soil. Workers in the tanneries suffer from gastrointestinal, dermatological, and other diseases, and 90% of this population dies before the age of 50. The presence of arsenic in the ground water increasing scarcity of fresh drinking water which causes skin lesion, kidney, liver complication, cancer etc.

The paper mill sludge produced by the paper industries are wet, sticky and had a strong odour. The moisture content in the sludge ranged from 45%–78% with an average of 65.08%. The composting of paper mill is recognized as the most adequate pre-treatment in order to obtain a material which may respond more efficiently with reduced odour and can help sanitize the material. The sludge contains CaCO₃ that could be helpful for the acid soil improvement by neutralizing the soil acidity. Due to the cellulosic fiber content application of sludge can hold moisture in the soil system. The electrical conductivity values of the six paper mill sludge ranged from 0.51–3.08 mS·cm⁻¹. This indicates that continuous application of sludge will increase soil salinity 

Paper mill sludge is usually disposed of in landfills. The total metal concentration is a poor indicator of metal bioavailability, mobility or toxicity, because these properties are strongly dependent on the chemical association of the individual components of the sample. Natural and anthropogenic environmental changes greatly influence the behaviour of metallic pollutants in sludge, as the form in which they occur may be change. Such external factors can include pH, temperature, the redox potential, organic matter decomposition, leaching, ion exchange processes and microbiological activity. In landfills, the pH may change due to the natural formation of acids during anaerobic microbiological degradation. Micro-organisms can alter the mobility of metals through reduction, accumulation, mobilization, and immobilization. During the re-use and long-term storage of wastes, acidification may be caused by sulfide oxidation, the buffering capacity of natural waters, acidic rainwater and atmospheric CO₂. If heavy metals are present in sludge in the loosely bound fraction, such as soluble, exchangeable and adsorbed forms, they tend to be mobilized.

The Ca and Mg contents ranged from 0.36%–1.28% and 0.41%–1.06%, respectively.

In the paper mill sludge, Na content ranged from 0.64% to 0.88%. Sodium is used in the pulping process as sodium hydroxide and Al is associated with the use of clays in the paper making process and the use of Al salts (e.g., aluminum sulfate) in the wastewater treatment process.

Total concentrations of heavy metals and micro-nutrients  were high in the paper mills with the exception of Cr.

High concentrations of nitrogen, phenol, chloride and heavy metals were detected in distillery sludge. If it is disposed in the soil without any treatment it will affect the soil properties by clogging soil micro-pores, decreasing soil microbial diversity.

Agricultural waste

Agricultural waste also called Green waste  is biodegradable waste that can be composed of garden or park waste, such as grass or flower cuttings and hedge trimmings, as well as domestic and commercial food waste and animal waste. The differentiation green identifies it as high in nitrogen, as opposed to  brown  waste,  which is primarily carbonaceous.

The constituents of animal biosolids typically contain

·         Strong organic content — much stronger than human sewage

·         High solids concentration

·         High nitrate and phosphorus content

·         Antibiotics

·         Synthetic hormones

Animal wastes from cattle can be produced as solid or semisolid manure or as a liquid slurry. The production of slurry is especially common in housed dairy cattle

Piggery waste

Piggery waste is comparable to other animal wastes and is processed as for general animal waste, except that many piggery wastes contain elevated levels of copper that can be toxic in the natural environment. The liquid fraction of the waste is frequently separated off and re-used in the piggery to avoid the prohibitively expensive costs of disposing of copper-rich liquid. Ascarid worms and their eggs are also common in piggery waste and can infect humans if wastewater treatment is ineffective.

Poultry waste

The production of poultry results in: hatchery wastes, manure (bird excrement), litter (bedding materials such as sawdust, wood shavings, straw and peanut or rice hulls), and on-farm mortalities. The processing of poultry results in additional waste materials, including offal (feathers, entrails and organs of slaughtered birds), processing wastewater and biosolids. Most of these by-products can provide organic and inorganic nutrients that are of value if managed and recycled properly, regardless of flock size. However, they also give rise to potential environmental and human health concerns as the sources of elements, compounds (including veterinary pharmaceuticals), vectors for insects and vermin, and pathogenic microorganisms. Specific concerns that are well documented include degradation of nearby surface and/or groundwater, resulting from increased loading of nutrients such as nitrogen and phosphorus (and potassium in some locations). Air quality issues include the fate and effect of ammonia, hydrogen sulphide, volatile organic compounds (VOCs) and dust particulates emitted from poultry production facilities.