University of Zimbabwe

University of Zimbabwe

Civil Engineering Department

Compiled By : Tsuro Charmaine

Supervisors 1st : Eng. Z. Hoko

2nd : Mr. Makaya

A proposal submitted in partial fulfillment of the requirements of

the Bsc. Honors in Civil Engineering

Abstract

Safe drinking water is a necessity to life, and so it becomes a mandate for the water utility to provide the resource within acceptable quality standards and quantity requirements to meet the needs of the consumer. The growing concern that many public water systems (PWS) are facing at the moment, including Zimbabwe National Water Authority (ZINWA), is that of providing enough water to meet demand at a reasonable cost whilst maintaining quality standards to protect public health(Finn, 2009). It therefore becomes of prime concern to investigate the contribution of water losses in reducing both quantity and quality of the resource in the distribution system, hence a justification of carrying out this project.

The project is in line with Millennium Development Goal number 7c which seeks to enhance environmental sustainability and halve the proportion of people without sustainable access to safe drinking water and basic sanitation by 2015(World Health Organization,2010). This research seeks to analyse the impact of water losses on the quality and quantity of water reticulated within the Centenary water distribution system.

Background of the Centenary Water Distribution

Centenary is a village in Mashonaland Central province in Zimbabwe, whose water distribution is managed by ZINWA. The community basically abstracts its water in the pick-up works from Musengedzi River, from which the raw water is then passed on into the purification works and eventually to the storage works upon which it reaches the consumers in the township and the suburbs respectively (Centenary W/S pipeline DWG WS-9-D4, 1980).

The distance through which the 150mm diameter raw water pumping main has to move from abstraction to the purification works is approximately 300m, whilst that from pure water pump house to the storage is approximately 5.7 km in length. In between this distance, the clear water is conveyed in 200mm diameter Asbestos Cement (A.C) pipes of varying classes. The area is mountainous, enabling the storage works to be situated between two big boulders on high ground such that distribution to the entire consumers is entirely due to gravity.

The reticulation system for Centenary is now suffering from ageing effects, being established in 1980 and coupled with the fact that there is poor maintenance. This is proving to be a major problem for this area as far as water losses are concerned. It should be noted that within Manyame catchment area, it is this town which presents a lot of trouble as far as losses in distribution are concerned presenting 8% station treatment losses and 61% reticulation losses (Nyakatembo, 2010).

Like any other distribution system, the management of Centenary Water supply requires careful attention to capacity, finance and water quality thereby necessitating an intense study into all possible losses occurring within the distribution as these affect proper functioning of the distribution channel. The main aim of carrying out this project is then to evaluate the water losses at characterized points in the Centenary distribution system so as to improve the quality and quantity of water reaching the demand centre.

Objectives

To satisfy the purposes outlined in the above, this research shall be broken down into four main objectives as indicated below.

Analysis of apparent and real water losses otherwise known as un-accounted forwater.

This shall involve a thorough investigation into both losses. As for the apparent losses, concentration shall be on the non physical losses that occur in utility operations due to customer meter inaccuracies, systematic data handling errors in customer billing systems and unauthorized consumption. Real losses on the other hand, shall include an investigation into leakage and storage overflows (American Water Works Association, 2010). All these losses mentioned in the above inflate ZINWAs production costs and stress water resources since they represent water that is extracted and treated, yet never reaches beneficial use. The investigation of such losses will therefore result in reduced revenue costs to the water utility.

Investigating the degradation of the quality ofwater

Leakages may result in the degradation of quality of treated water being distributed in the system, especially in cases where water loss occurs in areas exposed to high risk of contamination. Entry of subsoil or contaminated water through leaky pipes and joints especially in intermittent system may cause the degradation of water quality in the water distribution system (Water Treatments, 2008). It therefore becomes necessary to evaluate the relationship between quality of water received by the consumer to that being pumped into the distribution system before, and after the leakages.

Ensuring increase in the carrying capacity of the distribution system.

An investigation into the pipe network characteristics (age, length, size, material) is required so as to evaluate losses that may occur and possible changes in the quantity of water that may be received due to network ageing and population increase. Most problems which occur in a distribution channel are as a result of the distribution system being overwhelmed by the increase in loading due to increased demand. This will eventually result in the collapse of the system, hence need to study the networks characteristics so as to recommend increase in capacity where need be.

Ensuring adequate pressure at tail endsof the system.

Pressure in a distribution system should be properly managed as high pressures may result in excessive leakages and bursts, resulting in wasted resources and increased costs due to repairs as well as interruptions to customer supplies. Lower pressures may also enable a company to standardize on pipes and fittings which have a lower pressure rating and are therefore cheaper (Federation of Canadian Municipalities and National Research Council, 2003). Pressure control valves should be regularly maintained as they may have a large impact on water loss, similarly pressure relief valves should have their pressure set points regularly verified to ensure they do not open prematurely, thus wasting water. (Federation of Canadian Municipalities and National Research Council, 2003)

Methodology

At the moment, ZINWA does not use specialized equipment to measure losses occurring in the system. The key gadgets which can be used for estimating any losses that may occur within the system are the raw water master meter (which measures quantity of raw water into the sedimentation tank), clear water master meter (which quantifies water from sump into the reservoir) then the 80mm and 50mm bulk meters in the Gato township and suburbs distribution respectively (which quantify bulk water into the network).

A meter gauge also present within the distribution will aid in the estimation of losses. Within each propertys boundary, both external and internal meters are fitted, but for estimating losses only the external ones at property boundaries will be useful for assessing the supply pipe leakages. Other data from miscellaneous water taken in which may comprise of fire fighting and hydrant washing, sewer flushing and jetting, water main flushing and distribution system maintenance and in other cases building water and highway washing shall also be considered so as to reach an almost accurate percentage loss( Leak Detection Course 1997).

Quality testing of water shall also be carried out in areas where losses are expected so as to evaluate the degree of contamination, thereby giving a measure of the safety of water for various purposes.

References

Michael Finn 2009, Review draft control and mitigation of drinking water losses in distribution systems, United States Environmental Protection Agency, accessed 17 December 2010,

WHO 2010, WHO / Millennium Development Goals (MDGs), WHO, accessed 23 December 2010,

Nyakatembo, July 2010, Water loss Assessment at Centenary, Memorandum Ref W/S 266 presented to ZINWA Manyame Catchment Manager, Harare

American Water Works Association 2010, Apparent and Real Losses, American Water Works Association, accessed 17 December 2010, < http//www.awwa.org/Resources>

Federation of Canadian Municipalities and National Research Council 2003, Water Use and Loss in Water Distribution Systems, Federation of Canadian Municipalities and National Research Council, accessed 17 December 2010,

Leak Detection, Course handout distributed in the unit, Leak Detection, University of Zimbabwe Civil Engineering Department( Institute of Water and Sanitation Development), Mt. Pleasant on 15 Sept, 1997.

Water Treatments 2008, Degradation of Water Quality, Water Treatments, accessed 5 January 2011,

Reg. # (R076612L)

Evaluation of water losses at characterized points in a distribution system so as to improve the quality and quantity of water reaching the demand centre using Centenary Township as a case study.