Secondary treatment or biological treatment:
(i) The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into floc (masses of bacteria associated with fungal filaments to form mesh like structures).
(ii) BOD (Biochemical oxygen demand or Biological oxygen demand)ss. BOD refers to the amount of the oxygen that would be consumed, if all the organic matter in one litre of water were oxidized by bacteria.
(iii) The sewage water is treated till the BOD reduced. The greater the BOD of the water more is its polluting potential.
(iv) Once the BOD of sewage water is reduc significantly, the effluent is then pa into a settling tank where the bacteria "floes" are allowed to sediment, which is called activated sludge. A small part activated sludge is pumped back intoili aeration tank to serve as the inoculum.
(v) The remaining major part of the sludge pumped into large tanks called anaerel sludge digesters. Here, the bacteria Whi grow anaerobically, digest the bacteria the fungi in the sludge. During digestion bacteria produce a mixture of gases u as methane, hydrogen sulphide and CO which form biogas and can be used as source of energy.

Antibiotic resistance occurs when bacteria develop the ability to defeat the drug designed to kill or inhibit their growth. It is one of the most acute threats to public health. Antibiotic resistance is accelerated by the misuse and overuse of antibiotics, as well as poor infection prevention control. Antibiotics should be used only when prescribed by a certified health professional. When the bacteria become resistant, antibiotics cannot fight against them and the bacteria multiply. Narrow spectrum antibiotics are preferred over broad-spectrum antibiotics. They effectively and accurately target specific pathogenic organisms and are less likely to cause resistance.

(i) Antibiotics should be used only when prescribed by a certified health professional.
(ii) Narrow spectrum antibiotics are preferable since they effectively and accurately target specific pathogens and are less likely to cause resistance.

(i) It is an antibiotic produced by the fungus Penicillium notatum and Penicillium chrysogenum.
(ii) It is bactericidal in action and inhibits the synthesis of the bacterial cell wall.
(iii) It is the queen of drugs and was discovered by Alexander Flemming.

Cheese is a dairy product formed by coagulation of the milk protein, casein. During cheese production, milk is usually acidified and the enzyme rennet is added to cause coagulation. The solids are separated and pressed to form cheese. Most cheese are made with a starter bacteria, Lactococcus, Lactobacillus or Streptococcus.