Solution to Activity 13.2 of NCERT Class 7 Science Chapter 13 Wastewater Story:

2. Complete Activity 13.2 (Page 157). Locate an open drain near your home, school or on the roadside and inspect water flowing through it. Record colour, odour and any other observation. Discuss with your friends and your teacher and fill up the following Table 13.1.

Table 13.1 Contaminant survey

S. No	Type of sewage	Point of origin	Contaminants	Any other remark
1.	Sullage water	Kitchen
2.	Foul waste	Toilets
3.	Trade waste	Industrial and commercial organisations

Answer: The activity can be carried out in the following way:

Aim: To locate an open drain near your home record colour, odour and any other observation.

Materials Required: None

Procedure:

(i) Locate an open drain near your home, school or on the roadside and inspect water flowing through it. Use caution while doing this. Stand a safe distance away and avoid direct contact with the water. You can also do it under the supervision of an adult.

(ii) Record colour, odour and any other observation and fill in the Table 13.1

Observations:

Water was murky and brownish in colour.
There was a foul odour.
There was debris like floating plastic bags, wrappers, and other solid waste materials in the water.
There was a layer of oil on the surface.
The area around the open drain was littered with trash.

The completed table 13.1 is given below:

Table 13.1 Contaminant survey

S. No	Type of sewage	Point of origin	Contaminants	Any other remark
1.	Sullage water	Kitchen	Food remains, soap, oils, and grease.	Sullage water is less contaminated than foul waste.
2.	Foul waste	Toilets	Human faeces, animal waste, urea (urine), cleaning chemicals.	Higher concentration of pathogens, foul odour.
3.	Trade waste	Industrial and commercial organisations	Chemicals, heavy metals, oil, grease, and other pollutants.	Volume is higher and required complex treatment processes.

Conclusions:

Foul waste contains the highest amounts of pathogens among the three. Foul waste also has the highest odour. Requires rigorous treatment processes to remove pathogens.
Trade waste has contaminants of substances used industries and also undergoes complex treatment processes.

“Locate an open drain near your home, school or on the roadside and inspect water flowing through it. Record colour, odour and any other observation. Discuss with your friends and your teacher and fill up the following Table 13.1.” – Solved.