Assessment and design of a treatment process for the potable reuse of wastewater in Gaborone, Botswana
Date
2010-07-20T06:21:54Z
Authors
Wilson, John
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Abstract
Gaborone, Botswana is currently exploring the option of direct potable
reuse of wastewater to augment its drinking water supply. A feasibility
study has already been undertaken assessing this option and has
concluded that direct potable reuse is feasible. Based on this report and
an assessment of the possible options for reuse, an alternative design has
been developed integrating all levels of wastewater treatment.
The design integrates the different levels of wastewater treatment
compared to the existing proposed design and is based the following
points:
o Reuse will commence once the influent flows to the sewage
treatment works reach 65 000 m3/day, expected to be in 2012
o The future expansion of the sewage plant will provide two separate
treatment process trains, the existing conventional activated sludge
(CAS), and a new Membrane Biological Reactor (MBR).
o CAS will treat waste generated from the water reclamation plant,
whilst MBR treats screened raw sewage and provides disinfected
feed water to the plant
o The reclamation plant is comprised of 6 unit processes; cartridge
filtration, nanofiltration, reverse osmosis, UV disinfection,
stabilisation, and chlorination.
o Final product water will be blended with conventionally treated
surface waters from the Gaborone water works, with a maximum
35% of the blended water being reclaimed.
The report concludes that this design is more cost effective resulting in an
approximate saving of 15% on the overall costs over an 11-year period.