What is sewage? In which way can sewage be harmful to us?
Sewage is the municipal waste-water generated everyday in cities and towns. A major component of this waste water is human excreta. It contains large amounts of organic matter and microbes, many of which are pathogenic.
Sewage can be harmful to us in the following ways:
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When untreated sewage is discharged directly into natural water bodies like rivers and streams, it leads to their pollution.
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This causes an increase in water-borne diseases as the sewage contains pathogenic microbes that can spread infections.
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Due to increasing urbanisation, sewage is being produced in larger quantities, and the insufficient number of sewage treatment plants means more untreated sewage enters water bodies, posing health risks.
Explanation
The question has two parts: defining sewage and explaining its harmful effects. According to the textbook context, sewage is defined as municipal waste-water containing human excreta, organic matter, and pathogenic microbes. The harmful effects mentioned in the context include: (1) pollution of natural water bodies when untreated sewage is discharged, (2) increase in water-borne diseases due to pathogenic microbes, and (3) the growing problem due to urbanisation and inadequate treatment facilities. The answer is structured to address both parts clearly while staying within the 80-120 word limit appropriate for a 3-mark question.
Solution Steps
Step 1: Define sewage using the textbook definition - municipal waste-water with human excreta, organic matter and microbes
Step 2: Identify harmful effects from context - water pollution and water-borne diseases from untreated sewage discharge
Step 3: Structure answer with definition first, then harmful effects in separate paragraph with key terms bolded