Disinfection of Conducts

When a new pipeline is built, it should be submitted to a disinfection process before its use, in order to assure the maintenance of the water microbiological quality along its passage through the pipeline, complying the Portuguese legislation (Decree-law No. 23/95 of August 23rd).This disinfection aims to eliminate the microbiological load to which a pipeline is normally subjected during its construction process. There are several factors that contribute to the exposure of a pipeline to contamination:

• The sections and accessories of pipelines are usually stored on site at ground level and sometimes without joints at the ends;
• The weather conditions, for instance when it suddenly rains a lot, often cause flooding of the pipeline already placed, which usually no longer presents the buffered end;
• The habit of leaving the end of the pipeline free during the periods of stop work;
• The presence of wastewater pipelines near the ditch where the pipeline is being placed.

All the above factors, and others, may in fact contribute to the contamination of a pipeline, and should as far as possible be controlled, so that the probability of success of a disinfection is higher.

In traditional processes of disinfection chlorine is used as disinfectant agent, however this product cannot be directly discharged in the sewage system without neutralization, due to the chlorine content allowed in the wastewater (Decree-Law No. 236/98 of August 1st).

Manusystems commercializes and uses for the disinfection of water pipes the chlorine-free OX-Água 2ª Geração product, which is registered in the European System R4BP3 as biocide type 2, 4 and 5. In Portugal this product was evaluated by the Laboratório Central da EPAL, being included in its list of approved products for the disinfection of pipelines.

Execution Mode

Manusystems has developed a technical specification for water pipeline disinfection (ET-LDCN) that is being adopted by several water distributors. It will be made available to all interested parties.

The disinfection method of a new pipeline is as follows:

1. Filling the pipeline with water at low speed (around 0.2 m/s).
2. Washing the pipeline with water with a minimum speed of 1 m/s and ideal of 3 m/s, until clear water is obtained at every discharge points.
3. Filling the pipeline with disinfectant solution OX-Água 2ª Geração, with record of the disinfectant concentration along the pipeline.
4. Contact of the disinfectant solution with the pipeline (the contact time depends on the concentration of the solution).
5. After the contact time of the disinfectant solution, a new record of the concentration in disinfectant along the pipeline.
6. Discharge of the disinfectant solution (neutralization is not necessary when using OX-Água 2ª Geração).
7. Pipeline filling and final wash.
8. Control of the effectiveness of disinfection through bacteriological analyses in an accredited laboratory.

See also Equipment for Piping Disinfection!