- Physical: Sedimentation, filtration, storage
- Biological: Sand filtration, flocculation
- Chemical: Disinfection by chlorination
Clarification/Filtration: The Cawayan source uses a rapid sand filtration process. Raw water undergoes a combination of sedimentation and flocculation process before it is drained by gravity to the multi-layered silica sand and graded gravel filter media. Filtered water is transferred to a storage reservoir before it passes through a hypochlorination process, after it conducted by gravity to the distribution pipelines.
Back flushing is done twice a week by pumping clean water to a backwash tank located above the filtration system. Flushing is by gravity.
The Padurog and Sibanjan sources are set to undergo upgrading with the installation of modular filtration systems due for installation before end of 2015.
Disinfection: VWD uses chlorine powder to disinfect its water supply using the hypochlorinating machine. Dosing is 5 ml per cubic of filtered water. This amount is enough to give a reading of not less than 3 at all points of water testing and sampling.
Water Quality Monitoring
VWD regularly conducts bacteriological testing of all its ground and surface water sources. From several sampling points located strategically, a minimum of three (3) samples are taken weekly. With this process of water sampling, the LWD derives a good picture of the bacteriological quality of water supplied and distributed to the service area. All water samples are taken from fixed sampling points every month.
The location points is such that the water samples tested are representative of the water supplied to the distribution system and enables proper supervision and control of this bacteriological qualities of water. Such samples although not part of the regular sampling frequency are not used as a basis for evaluation of the bacteriological quality of water supply.
The bacteriological analysis of water is the most valuable examination and is vital in preventing epidemic brought by water pollution. Representative samples are sent to a qualified laboratory for the estimation of bacterial estimation of bacterial density. The coliform group includes all aerobic, facultative, anaerobic gram negative non-spore forming bacilli, which ferment lactose broth with gas formation. Formation of gas in the lactose broth media within 24 hours is the presumptive evidence of the presence of the number of group. This service is undertaken by a private entity.Service quality
All areas of VWD’s piped systems are served 24 x 7, with the exception of the northern barangays serviced by the Cawayan source. These areas suffer intermittent services especially during extremely dry months, exacerbated by undersupply and low water pressure during peak hours. This can be attributed to the already strained supply from the source. However, water supply is augmented by the two underground sources and a newly acquired water tank truck that also supplies other areas with very low water pressure.
Currently, the District has managed to keep down its NRW to manageable levels. Even with an ageing and leaky piping system, maintenance crews have been effectively plugging many of the transmission and distribution problems.
Collection efficiency is maintained, which include arrearages and current accounts and revenue losses from illegal connections are comparatively low.