Quality Assurance

RESPONSIBILITIES OF THE LAB UNITS

The Lab Unit is responsible to establish standards for bacteriological and chemical quality, monitoring and developing sampling frequencies from distribution network and testing procedures to be followed within the parameter of WHO. The process control aspects of water treatment are of vital importance in providing water supply to the people of Karachi. Lab Facilities have been provided at all water treatment plants for monitoring chemical dosing (chlorination) and maintaining quality control according to WHO guidelines. In addition KWSB central Lab at C.O.D. Hills Filter plants for monitors the bacteriological quality of city water by collection and testing 900-1000 samples per month, from the city distribution net work. .Lab. report indicate that quality of water is within the prescribed WHO limits, however isolated cases of contamination are promptly attended by distribution engineers. Assistance is also provided to residents of Karachi by testing well water advising subsequently. The objective of the lab unit is to following the measures of accomplishment regarding physical, chemical and bacteriological quality of potable water.

PROCEDURE OF LAB REPORT FOR RAW & FILTER WATER AT FILTER PLANTS:

• The samples are taken from raw influent at inflow of Filter Plants and tested in the Laboratories.
• Almost all the samples of raw water are not fit for domestic use.
• Therefore, is given treatment through sedimentation, filtration at each Filter Plant.
• Disinfections by means of pre and post chlorination is made in order to bring it quality as per WHO standards / guidelines.
• Post-filtration Chlorination treatment is provided at Filter Plants as a safe guard against contaminations.
• Residual chlorine is usually applied between 1.0 to 2.0 ppm at the reservoir outlet to overcome the contaminations / bacteria added in distribution network before reaching in the houses of consumers.
• The residual chlorine is available between ” 0.20 to ppm & traces” throughout the distribution.

For raw and filter water General treatment methodology for drinking water as per engineering technology:

(a) Mechanical
(b) Chemical
(c) Physical (Boiling)
(d) Radiation

SOURCES OF CONTAMINATION OF TREATED DRINKING WATER

Water in the distribution system may become contaminated through Cross connections

• Back siphon age
• Leaking service connection
• Defective storage tanks and reservoirs
• Damaged hydrants
• Utilization of un-authorize suction pumps
• Inexpert repairs to domestic plumping system

In 1984 WHO introduced a new set of “drinking water quality recommendation” These are not presented as standards but rather guideline criteria which can serve as a basis for preparation of local standards.

MEASURES TAKEN BY KWSB AGAINST CONTAMINATION

The KWSB immediately after it’s creation has taken a number of measures of ensure supply hygienically fit water to the city of Karachi as follows.

1. The minimum requirements of free chlorine in the distribution system according to WHO standards is 0.25 to 0.50 ppm. However, KWSB maintains 2.00 ppm residual (free) chlorine at the reservoir outlets in order to ensure that the minimum of free chlorine requirement is maintain throughout the distribution network, This is the best guard against contamination.
2. 1000 Nos. water samples are now being collected every month for bacteriological analysis. The testing for quality of water is regularly carried out in KWSB laboratory at COD Hills Filtered Plant.
3. The Board has introduced a system of ‘counter check’ and periodically samples are tested at the Karachi University and Pakistan Council of Scientific and Industrial Research (PCSIR).
4. The complaints of contamination are given priority and immediate remedial measures are adopted by expositing the line to locate the cause.

RE-TREATMENT PROCESS ADOPTED KWSB

Patterson and Candys water treatment plants were acquired under the Hilaya Scheme whereas WABAG and Degramont plants from West Germany and France respectively have been installed under the 1st, 2nd and 3rd Phase of the Greater Karachi Bulk Water Supply Scheme. All these plants work on the principle of the pre and post chlorination, coagulation and precipitation of settled matter in sedimentation basin and further purification in rapid sand filter beds. Row and Candys water is received in a distribution chamber for treatment, to chlorination. The chlorination results in the reduction of organic and bacterial load as well as in optimization of the Ph value for effective and economical use of the coagulant Aluminum soleplate, which is used as a coagulating agent. is introduced in the raw water before a flash mixer for uniform distribution of the coagulant in the water body. The chemically mixed water is then conveyed to a flocculation unit for preparation of a thick and heavy flock of settle able matter. This Unit has a retention time of 20-30 minutes. The heavy flock is separated and removed in sedimentation basin . Circular and rectangular clarification tanks having a detention time of 2-3 hours have been installed in the Patterson and candy’s and WABAG treatment plants were the heavier flock settles down and is removed by mechanical, rakes under hydrostatic pressure. The Decrement plants have pulsators for removal of settle able matter where the heavy flock is not allowed to settle at the bottom but is kept in suspension upto 2/3rd of the height of the water column by means of regular intermittent pulsations applied to the water body. The upward flow of water, also assists in the connections by hydro-static pressure through automatically operated and controlled sluice valves. The clarified water is then provided further treatment in rapid send filter beds. The water collected at the bottom of the filter is potable and according to WHO standards. How-ever, post chlorination is applied before storage in reservoirs for distribution in the city. For effective treatment and quality control, during the treatment processes and for ensuring a safe and potable water supply to the city. The KWSB is maintaining chemical laboratory at all treatment plants. Extensive check on the sanitary quality of the city water supply are made. Approximately 30 bacteriological examination at the main KWSB laboratory laboratory at COD Hills Filter Plants. In addition further monitoring is carried out by independent agencies KMC. Karachi University and PCSIR and EPA.

COMMUNITY & SCIENTIFIC METHOD FOR PURIFICATION AND STORAGE OF SAFE WATER

BULK WATER SUPPLY SYSTEMS OF KARACHI WATER & SEWERAGE BOARD