Download App

STD 12 - 8. microbes in human welfare — NEET STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceNEETSTD 12 - 8. microbes in human welfare4 Marks
MCQ
The domestic sewage in large cities
  • A
    has a high $BOD$ as it contains both aerobic and anaerobic bacteria
  • ✓
    is processed by aerobic and then anaerobic bacteria in the secondary treatment in Sewage Treatment Plants $(STPs)$
  • C
    when treated in $STPs$ does not really require the aeration step as the sewage contains adequate oxygen
  • D
    has very high amount of suspended solids and dissolved salts.
✓

Answer

Correct option: B.
is processed by aerobic and then anaerobic bacteria in the secondary treatment in Sewage Treatment Plants $(STPs)$
b
(b) : Sewage water can be purified by passing it through sewage treatment plants with the action of heterotrophic microorganisms. There are three stagesof this treatment -primary, secondary and tertiary. Primary treatment removes floating and suspended solids from sewage through two processes of filtration and sedimentation. First floating matter is removed through sequential filtration. The filtrate is kept in large open settling tanks where grit settles down. The sediment is called primary sludge while the supernatant is called effluent. The primary sludge traps a lot of microbes and debris. In secondary treatment, the primary effluent is taken to aeration tanks. A large number of aerobic heterotrophic microbes grow in the aeration tank. They form flocs. Flocs are masses of bacteria held together by slime and fungal filaments to form mesh like structures. The microbes digest a lot of organic matter, converting it into microbial biomass and releasing a lot of minerals. As the $BOD$ of the waste matter is reduced to $10-­15\%$ of raw sewage, it is passed into settling tank. Thus secondary treatment is more or less biological. The sediment of settling tank is called activated sludge. The remaining is passed into a large tank called anaerobic sludge digester. It is designed for continuous operation. The aerobic microbes present in the sludge get killed. Anaerobic microbes digest the organic mass as well as aerobic microbes of the sludge. They are of two types, nonmethanogenic and methanogenic. Methanogenic bacteria produce a mixture of gases containing methane, $H_2S$ and $CO_2$.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

NEET STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

Assertion: Bone marrow and thymus are primary lymphoid organs.
Reason: It provides the sites for interaction of lymphocytes with the antigen.
→
Trisomic condition of Down's syndrome arises due to
→
Statement I: The body of a simple organism like Hydra have tissue organisation.
Statement II: In this animal, a group of similar cells along with intercellular substances perform a specific function.
→
Cell aggregate body plan is found in the
→
Mark the given statements True (T) or False (F).
(i) Squamous epithelium is found in wall of blood vessels and air sacs of lungs.
(ii) Cuboidal epithelium is found in ducts of glands and Henle's loop of nephrons.
(iii) Columnar epithelium lines the inner surface of stomach and intestine.
(iv) The columnar or cuboidal cells bearing cilia on their surface are called ciliated epithelium and are present in inner surface of solid organs like bronchioles and fallopian tubes.
(V) The goblet cells of alimentary canal has unicellular type of glandular epithelium whereas salivary gland has multicellular type.
(vi) Compound epithelium covers the dry surface of the skin, moist surface of buccal cavity, pharynx, innerlining of duct of salivary gland and of pancreatic duct.
(vii) Tight junctions help to stop substances from leaking across a tissue whereas gap junction facilitate cells to communicate with each other by connecting the cytoplasms of adjoining cells.
(viii) Adhering junctions performs cementing to keep neighbouring cells together.
(ix) In all connective tissue the cells secrete fibres of structural proteins called collagen or elastin.
(x) Tendon attach skeletal muscles to bones and ligament attach one bone to another and both are example of loose regular type of connective tissue,
(xi) The cells of cartilage called chondrocytes are enclosed in large cavities within matrix secreted by them.
(xii) The cells of bone called osteocytes are present in the spaces called lacunae.
(xiii) The bone-marrow in all bone is the site of production of blood cells.
(xiv) The fibres of muscle tissue are composed of numerous fine fibrils, called myofibrils,
(xv) The smooth muscle fibres taper at both ends (fusiform) and show striation.
Choose the correct option given below :-
→
Difference between $ZIFT$ and $IUT$ lies in the
→
Infection of pneumonia occurs due to
→
Insects have blood which
→
Genetic equilibrium means
→
Metamerism is characteristic of
→