Upload Now
The below mentioned article provides quick notes on Solid Waste Bio-Treatment.
The implementation of increasingly stringent standards for the discharge of wastes into the environment, as well as the increase in cost of habitual disposal or treatment options, has motivated the development of different processes for the production of goods and for the treatment and disposal of wastes.
These processes are developed to meet one or more of the following objectives:
1. To improve the efficiency of utilization of raw materials, thereby conserving resources and reducing costs
2. To recycle waste streams within a given facility and to minimize the need for effluent disposal
3. To reduce the quantity and maximize the quality of effluent waste streams that are created during production of goods
4. To transform wastes into marketable products.
The multitudes of ways in which the transformation of wastes and pollutants may be carried out can be classified as being chemical or biological in nature. Bio-treatment can be used to detoxify waste streams at the source-before they contaminate the environment-rather than at the point of disposal.
In fact, waste represents one of the key intervention points of the potential use of environmental biotechnology. Bio-waste is generated from various anthropogenic activities (households, agriculture, horticulture, forestry, waste water treatment plants), and can be categorized as: manures, raw plant matter, process waste.
Biological waste treatment aims to the decomposition of bio-waste by organisms in more stable, bulk-reduced material,which contributes to:
a. Reducing the potential for adverse effects to the environment or human health
b. Reclaiming valuable minerals for reuse
c. Generating a useful end product.
Advantages of the biological treatment include:
a. Stabilization of the waste
b. Reduced volume in the waste material
c. Destruction of pathogens in the waste material
d. Production of biogas for energy use.
The end products of the biological treatment can, depending on its quality, be recycled as fertilizer and soil amendment, or disposed. Solid waste can be treated by biochemical means, either in situ or ex situ . The treatments could be performed as aerobic or anaerobic depending on whether the process requires oxygen or not.
1. Anaerobic Digestion:
Anaerobic digestion of organic waste accelerates the natural decomposition of organic material without oxygen by maintaining the temperature, moisture content and pH close to their optimum values. Generated CH4 can be used to produce heat and electricity.
The most common applications of solid-waste bio-treatment include:
a. The anaerobic treatment of biogenic waste from human settlements
b. The co-fermentation of separately collected biodegradable waste with agricultural and/or industrial solid and liquid waste
c. Co-fermentation of separately collected biodegradable waste in the digesting towers of municipal waste treatment facilities
d. Fermentation of the residual mixed waste fraction within the scope of a mechanical- biological waste-treatment concept.
Anaerobic processes consume less energy, produce low excess sludge, and maintain enclosure of odour over conventional aerobic process. This technique is also suitable when the organic content of the liquid effluent is high. The activity of anaerobic microbes can be technologically exploited under different sets of conditions and in different kinds of processes, all of which, however, rely on the exclusion of oxygen.
2. Composting:
The biological decomposition of the organic compounds of wastes under controlled aerobic conditions by composting is largely applied for waste bio-treatment. The effective recycling of bio-waste through composting or digestion can transform a potentially problematic ‘waste’ into a valuable ‘product’ compost.
Almost any organic waste can be treated by this method, which results in end products as biologically stable humus-like product for use as a soil conditioner, fertilizer, bio-filter material, or fuel. Degradation of the organic compounds in waste during composting is initiated predominately by a very dissimilar community of microorganisms: bacteria, actinomyctes, and fungi.
An additional inoculum for the composting process is not generally necessary, because of the high number of microorganisms in the waste itself and their short generation time. A large fraction of the degradable organic carbon (DOC) in the waste material is converted into carbon dioxide (CO2). CH4 is formed in anaerobic sections of the compost, but it is oxidized to a large extent in the aerobic sections of the compost.
The estimated CH4 released into the atmosphere ranges from less than 1% to a few per cent of the initial carbon content in the material .Composting can lead to waste stabilization, volume and mass reduction, drying, elimination of phytotoxic substances and undesired seeds and plant parts, and sanitation. Composting is also a method for restoration of contaminated soils.
Source separated bio-wastes can be converted to a valuable resource by composting or anaerobic digestion.
In recent years, both processes have seen remarkable developments in terms of process design and control. In many respects, composting and digestion differ from other waste management processes in that they can be carried out at varying scales of size and complexity. Therefore, this enables regions to implement a range of different solutions: large and small-scale systems, a centralized or decentralized approach.