OVERVIEW
Drinking water needs to have a pH of about 7 for effective treatment. During the process of water treatment, alum is added to remove organic particles and clay in the process of flocculation. Alum decreases the pH of water making it acidic for low alkaline waters. Moreover, the neccessary alum dosage is very sensitive to pH changes in the entering water and vice versa. This is often the case in many of the Honduran plants. For this reason it is imperative to ensure that the pH of the water entering the flocculator is maintained near 7. Lime ( Calcium Hydroxide) is an alkaline substance popularly used to neutralize low pH water. By devising a system (lime feeder) which will continuously supply a dose of saturated lime into the entrance tank, the target pH of the water as desired.
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OBJECTIVE
The main objective of the team is to design a lime feeder system to deliver effluent with a pH of around 12 +(saturated pH of water) to be mixed in with treated water to increase its pH. For efficient plant operation, the lime feeder design must be simple, easy to construct and install, and be cost-effective while also being robust enough as to avoid using electricity and to not require maintenance more than once a day.
INTRODUCTION
The former ANC group experimented on different designs for a lime feeder, including a column model, a conical vessel, a funnel - column and lastly an inverted traffic cone model. The most effective design was the inverted cone because it supplied saturated limewater at a pH between 11 and 12 for about 18 hours without having to be unclogged. However, the main problem with this setup is that inverted cones are extremely difficult and expensive to construct, install and maintain. Every other model also had its problems and drawbacks.
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