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The proper sanitation of the final effluent at a Sewage plant is of utmost importance due to the fact that this water is released into the environment. Failure to do proper sanitation will have serious health implications for both people and animals that might be exposed to the water. Sodium Hypochlorite was dosed firstly via a gravity feed system and then through a chemical dosing pump. Due to the small feed rates the Sodium Hypochlorite would crystallize in low flow areas resulting in blockages and hence no sanitation takes place. The customer in question approached Arch Chemicals (Pty) Ltd to propose alternatives to both the chemistry and dosing equipment.



Based on the plant data, the required dosage was calculated and the appropriate dosing system was chosen. In this case the Pulsar® 1 System plus the Pulsar Briquettes would give an adequate dosing rate in order to maintain the required Chlorine residuals.

System data:

  • Plant flow rate = 70 800 liters per hour (1,7 Mega liters per day)
  • Initial dosage  = 3 parts per million
  • Available Chlorine required = 7.8 kg/day
  • Pulsar® 1 Capacity = 11.4 kg/day
  • Initial Rotameter setting = 3,0 liters per minute

The Pulsar® 1 unit was installed utilizing a centrifugal pump for recirculation, and installing the Venturi system on the recirculating line. Picture 1 shows the pump and Venturi arrangement.


Recirculating Pump and Venturi System

Picture 2 shows the actual Pulsar® 1 Unit is an enclosure. Note the Rotameter to the left of the unit and out of picture is the control valve from which the dosing rate is controlled. Dosing will be controlled by measuring the residual Chlorine in the final effluent and the adjusting the flow through the Pulsar® 1 unit accordingly.


Pulsar® 1 Unit 


With the switch to Pulsar® 1 System and briquettes the dosing problems are solved. The system provides the following:

  • Enhanced Operator Safety – less potential hazards
  • Long Shelf Life – Briquettes have a 2 year shelf life whereas NaOCl can show signs of degradation in less than 30 days
  • Superior Chemical Make-up – Proven wave technology
  • User-Friendly System – Low maintenance and ease of operation