Few problems along with their solutions from this chapter are given follows:
Q.┬аMethanogenic bacteria are not found in
(a) rumen of cattle┬а┬а┬а┬а┬а┬а┬а┬а┬а ┬а┬а(b) gobar gas plant
(c) bottom of water-logged paddy fields ┬а(d) activated sludge
Ans.┬а(d) activated sludge┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а
Methanogenic bacteria (that produce methane) are not found in activated sludge. The microbes present in the activated sludge are aerobic bacteria that grow rapidly and form flocs.
During secondary treatment of wastewater it is in the digesters where other kinds of bacteria which grow anaerobically, digest the bacteria and the fungi in the sludge producing mixture of gases such as methane, hydrogen sulphide and CO2┬аwhich form the biogas.
Q.┬аWhy do we prefer to call secondary waste water treatment as biological treatment?
Ans.┬аSecondary waste water treatment is called biological treatment because microorganisms are involved in the breakdown of organic matter in this phase of waste water treatment.
The primary effluent is passed into large aeration tanks where the organic matter in it is consumed by aerobic microbes which are later themselves digested by anaerobic bacteria and fungi in anaerobic sludge digesters.
Q.┬аWhy is distillation required for producing certain alcoholic drinks?
Ans.┬аDepending on the type of the raw material used for fermentation and the type of processing (with or without distillation) different types of alcoholic drinks are obtained.
Wine and beer are produced without distillation whereas whiskey, brandy and rum are produced by distillation of the fermented broth.
Distillation removes most of the water and impurities from certain alcoholic drinks. That's why for producing certain alcoholic drinks, distillation is required.
Question. 14┬аWhat are biofertiilisers? Give two examples.
Answer.┬аBiofertiilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.┬аe.g.,
- Azospihllum, Rhizobium and Azotobacter can fix atmospheric nitrogen in the soil.
- Blue-green algae like Anabaena, Nostoc, Occilatoria add organic matter to the soil and are responsible for increasing its fertility.