Problem

Disinfection of the semi treated water with chlorine gas could be interrupted by either planned - or unplanned events which include the following:

1. Planned interruptions

• Maintenance on chlorine gas dosing system.
• Cutting new lines into existing lines of carriage water.

2. Unplanned interruptions

• Isolated power trip on chlorine gas systems.
• No carriage water available for injectors due to pipe bursts.
• Evaporators’ breakdown.
• Chlorine gas leaks.
• Change-over valves on chlorine gas banks stuck.

In the above mentioned emergency events, it is not possible to continue Chlorine gas dosage at the suction head after the sand filters (Station 4) or in the suction ring with injectors feeding the main pumps (Station 1 & 3). An alternative disinfection program then needs to be followed in order to supply water quality that is within the specifications mentioned in point 3.

HTH® Industrial feeders installed at 3 locations at the Zuikerbosch plant; Station 1, 3 and 4 - the solution to this problem. These feeders have each a capacity of 180-kg HTH® Scientific chips and at full dosage, dissolve more than 30-kg of HTH Scientific chips per hour without the help of electricity. This dissolved calcium hypochlorite solution is then gravity fed to the semi-treated water that needs to be chlorinated.

At Station 4, nine (9) of these gravity feeders are installed to treat 30 mega liter water in the underground reservoir.  These feeders are installed on top of the reservoir (see Fig. 1), and gravity feed dissolved HTH® Scientific product into the reservoir, chlorinating the water within the specified concentration.

Fig. 1  Industrial Feeder at RWB Zuikerbosch Station 4

At station 3, three (3) feeders are installed on each side of the overflow tower in the suction ring after the 64 filter’s reservoir. Each set of 8 filters have a 16 Ml reservoir and chlorination takes place after the filters in the suction ring feeding the main pumps. In total 128 Ml reservoir water to be treated at this station.

At station 1, four (4) feeders are installed and chlorination takes place on the suction ring feeding the main pumps.

HTH® Industrial feeders are really effective as a back-up chlorination system and control the Chlorine residual levels within Rand Water specifications.

Benefits

1. No handling of liquid chemicals.
2. Tailor made for every application need.
3. No electricity needed; gravity feed.
4. Low risk installation.
5. Easy, cost effective installation.
6. Continuous chemical dosing ensures safe drinking water.
7. The HTH® Industrial feeder has proven reliability.
8. Dosage can be regulated with flow through rotameter.