Cleaning > Analysis Report

Which Operational Procedure benefits your Organisation?

Effective Cleaning of Water Mains

Which method works best and why? Compare the results

Water authorities and service providers have differing views on the most effective methods for cleaning potable water reticulation and transmission mains. So we put it to test!

In this test the same section of pipe was cleaned three times in succession. The water quality was tested during each procedure, and again after the mains were re-charged and placed back on line. We employed the following cleaning methods.
1. Flushing
2. Air Scouring
3. Pipeline Pigging

1. FLUSHING

When flushing a pipe section the line is opened to atmosphere at full flowand pressure. The high velocity flow rate is designed to dislodge and remove debris and turbidity from the internal bore. It was found that whilst this method provided some cleaning efficiency, it used large volumes of water and the majority of debris was not removed. The procedure was found to be both inefficient and ineffective when compared to the methods used in this exercise.

2. AIR SCOURING

Air Scouring uses turbulent flow to clean the mains by introducing a balanced mixture of clean filtered air and water into the pipeline.

This method is far more effective and efficient than Flushing, and is particularly suited to smaller pipe diameters up to DN200. The introduced turbulence removed debris such as bio-films, scale, rust, silt and other contaminants. As the results show this procedure was more efficient than Flushing and provided a significantly better result when the water was tested.

3. PIPELINE PIGGING

This specialised technology utilises Pipeline Pigs, devices that are propelled through the line to clear and clean debris from the internal bore. Many different types of Pipeline Pigs are available to cater for a range of duties. In some cases Pipeline Pigs are capable of deforming by up to 80% of their original size and are often used in Multi-Diameter Pipelines. Pipeline Pigs can be used over varying distances which proves to be cost-effective against other cleaning methods.

The results from cleaning the same pipe section employing Pipeline Pigs during this exercise proved most successful. The levels of suspended solids, COD and other impuritiesremoved from the line were many times greater than those achieved by Flushing or Air Scouring.

As the test results show Pipeline Pigging is far superior to Flushing and superior to Air Scouring. The costs associated with Pipeline Pigging may be higher than the other methods however the net cost is comparable as the frequency of cleaning cycles is significantly reduced due to the high levels of cleanliness achieved.

Recharging – a procedure conducted after the above operations were completed and normal water flow was returned.

Test samples were taken during each process and then after the mains had been recharged and back online
sample date: 20/07/2000 Flushing Air Scouring Pigging Recharging
 sample type grab grab grab grab
 pH (mg/L) 7.0 7.1 7.3 7.5
 suspended solids 309 110 3920 -4
 COD 24 11 931 5
 total Phosphorous 0.2 0.3 1.2 -0.1
 Kjeidahl N 2.2 1.3 24.6 1.6
 Nitrite N -0.1 0.6 0.7 -0.1
 Nitrate N 0.3 0.1 -0.1 -0.1
 total Nitrogen 2.5 2.0 25.3 1.6
 Aluminium 0.27 0.10 9.9 -0.05
 
 
 

 


















Notes

  • pH neutral is 7… less than pH 7 the water becomes acidic and breaks down chloride.
  • A higher pH level than 7 is alkaline and 7.5 is considered to be a good
    level.
  • Suspended solids reading of less than 20ppm after cleaning is deemed acceptable.
  • COD (chemical oxygen demand) is a chemical analysis of water. The more chemicals there are in the water, the more oxygen levels are decreased and this can lead to the water becoming stale or odorous. Less than 100g is considered acceptable.
  • Total Phosphorous measures the amount of organic material and bacteria in the water.
  • Nitrite levels are produced if Nitrate levels are high.
  • If Nitrate is high this will encourage growths such as algae.
  • Total Nitrogen is the total of nitrogens present as above.
  • Alum is used for water clarity. The Aluminium readings above were found tobe present in Alum.

A clean pipeline is not only important, it is necessary. A clean pipeline protects your investment and allows that investment to produce long-term revenue. It reduces your operating cost, which in turn allows you to maximise your profit.