CHLORINE DIOXIDE DOSING SYSTEM

Introduction

Chlorine Dioxide is a powerful oxidant most commonly used as a disinfectant in cases where problems of taste and odour can occur with the use of Chlorine, particularly those due to the presence of Phenols. It does not produce trihalomethanes (THMs) or react with ammonia that may be in the water, which form Monochoramines (NH₂CI). It has a bacterial efficiency comparable with that of free chlorine in the neutral pH range, however unlike chlorine, its efficiency increases as the pH rises. Another important fact is that it is extremely soluble in water, being five times more soluble than chlorine.

Used commercially in aqueous solution rather than gas due to its explosiveness when exposed to rising temperatures, exposure to light or allowed to come into contact with organic substances. In aqueous solution it is completely harmless and will not react chemically with water, as would chlorine. It can be used up to a maximum dose level of 0.5ppm for drinking water disinfection, and has a particular advantage where phenols are likely to cause taste problems or in waters which have high pH or ammonia levels. Chlorine dioxide residuals are easily removed from water by airation and will quickly deteriorate when the water is in an open vessel, leaving a negligible amount of chloric acid (HCLO₃).

Application

Chlorine dioxide is produced at the point of application by mixing stabilised chlorine dioxide donor liquid and acid activator.

The unit we supply utilises a specially designed uPVC injector with an integral reaction chamber to ensure that the chlorine dioxide is fully formed by the intimate mixing of the donor chemical and activator before the chemicals make contact with water.

This arrangement eliminates the storage and pumping of activated CLO₂ solutions and ensures full conversion and activation of the chlorine dioxide donor product.

The injector can be installed to dose direct into pipework or suspended in a tank or cooling tower pond.

The control system requires a volt free impulse signal from a water meter or chlorine dioxide monitor to initiate dosing of the stabilised chlorine dioxide and activator to the injector block in proportion to the water flow. (A range of flow meters and monitors are available, details upon request)

Chemicals are drawn direct from supply drums or chemical tanks via suction lances equipped with liquid level detectors. The liquid level detectors provide a low chemical alarm and inhibit the chemical pumps to prevent inappropriate dosage and avoid the need to reprime pumps.

The central processor controller is configured to dose in proportional to water flow, requiring an impulse signal from a water meter. (Time controlled option available upon request.)

A text display/operator interface, mounted on the front of the control panel, provides operator information as the system status and set up data.

The system is housed in three ABS enclosures connected side by side. The centre section houses the central processor and control; with the side enclosures house the two chemical pumps. This layout ensures effective isolation of the two chemical pumps preventing any premature mixing of the two chemicals.

Technical Specification

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