Draw a diagrammatic sketch of biogas plant and label its various components given below gas holder, sludge chamber, digester, dung + water chamber.
The raw material for biogas production is excreta (dung) of cattle. The biogas plant has a concrete tank (10-15 feet deep) in which bio-wastes and slurry of dung is collected.
The tank has a floating cover which rises on production of gas in the tank. Methanobacterium in the dung act on the bio-wastes to produce biogas. The gas produced is supplied to nearby houses by an outlet. Through another outlet, the spent slurry is removed to be used as fertiliser. Biogas is used as fuel for cooking and lighting.
Describe the main ideas behind the biological control of pests and diseases.
It's a natural and eco-friendly concept. If employs the use of organisms to control the population of pathogens and pests in an ecosystem. Classical examples are Trichoderma which is antagonist, i.e., against many soil borne plant pathogens.
Similarly, Penicillium inhibits the growth of Staphylococcus and therefore has been successfully used in the production of penicillin antibiotic to control many human bacterial pathogens. Bacillus thuringiensis acts as biopesticide to control insect.
Baculovirus used as biological control agents in genus Nucleo-polyhedrovirus are excellent for species-specific-narrow spectrum insecticidal application. The overall biological control of pest is considered much more beneficial in an ecological sensitive area.
(a) What would happen if a large volume of untreated sewage is discharged into a river?
(b) In what way anaerobic sludge diagestion is important in sewage treatments?
(a) If untreated sewage is discharged directly into rivers it will lead to serious pollution of the waters with organic matter and pathogenic bacteria, Protozoa and many other diseaser.
This water, if used, will cause outbreaks of water borne diseases.
(b) In anaerobic sludge digestion, anaerobic bacteria, digest the aerobic bacteria and the fungi in the sludge and the remaining organic matter.
During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases (biogas) can be used as source of energy as it is inflammable.
Which type of food would have lactic acid bacteria? Discuss their useful application.
The most common food item that are curd, and yoghurt contain Lactic Acid Bacteria (LAB) of Lactobacillus species. Curd is formed by adding a small amount of curd to milk, which acts as a starter. Microbes present in starter multiply at suitable temperature and convert milk into curd.
Acids released by LAB during the growth coagulate and partially digest milk protein, casein thus increases the digestibility of milk protein.
Application of LAB
(i) Improves nutritional quality of milk by increasing vitamin- $\mathrm{B}_{12}$.
(ii) Checks disease-causing microbes in stomach.