Question

Q1. Gombo Water and Sanitation Company Limited has been having a problem with regards to the operation of
the company which has caused the organization not to satisfy the needs of the customers due to frequent
breakdown of water and sewerage pumps, residents receiving brownish water and not addressing customer
complaints of high bills, residents not receiving adequate supply of water and leakages in the distribution.
The other problem has been frequent sewerage blockages which results in direct discharge of raw sewerage
into the Mulungushi River hence affecting the ecological process as the main sewerage pipe crosses the
river. In May this year, the company was given a fine by Environmental Management Agency of 50,000
Zambian Kwacha for discharging raw sewerage in the Mulungushi River due to non-function of the
Biological filters. You have been engaged as a consultant by the Government of the Republic of Zambia to
provide solutions to the challenges the utility is facing. What professional advice would you give?

Answer 1

In this problem water and Sanitation company is supplying water to households and collecting the sewage from households. Many complaints are there from customers and also the sewerage treatment plant is not efficient.

• First rearrange the water supply and treatment system in scientific way
• Calculate water demand of the society and fix (normally 135 litres per capita is sufficient) the water supply system. For water supply storage tank the capacity is generally 1/3 rd of total demand. So pumping is done 3 times in a day. After finding storage tank capacity pump power is calculated for peak flow.
• Pump power = WQH/efficiency, W= Density of water (N/m3), Q =peak flow of water (m3/s), H = head (m)
• After that diameter of water supply pipes should be calculated using Hazen Williams nomogram
• Water treatment plant shoul be designed from outfall to households
• Try to make treatment system without river crossing, if not possible provide primary treatment tank before crossing river and provide aqueduct for carrying sewerage across river.
• Ensure operation and maintenance of treatment plants (proper backwashing)
• To rectify the social issues provide a committee in which representative of consumers, company stafff and government should present. Committee can make a fund for rectifying operation and maintenance issues.