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Class 12th Biology 2018 Set1 Delhi Board Paper Solution

Question 8

How did a citizen group called Friends of Arcata Marsh, Arcata, California, USA, help to improve water quality of the marshland using integrated Waste Water Treatment? Explain in four steps.


Waste water including sewage can be treated in an integrated manner, by utilising a mix  of artifical and natural processes.

(a) The conventional sedimentation, filtering and chlorine treatments are given. After this stage lots of dangerous pollutants like dissolved heavy metals still remain.

(b) To combat this, an innovative approach was taken and the biologists developed a series of 6 connected marshes over 60 hectares of marshland

(c) Appropriate plants, algae becteria and fungi were seeded Into this area, which neutralize,absorb and assimilate the pollutants. Hence, as the water flows through marshes, it gets purified naturally.

(d) The marshes also constitutes a sanctuary with a high level of biodiversity in the form of fishes, animals and birds.