Control of Manganese and Ammonia in Drinking Water

The Town of Saint-Pie (QC, Canada) has a potable water distribution system that is supplied by an 11.7-acre (4.7 ha) reservoir located at the top of Mount-Yamaska. This reservoir was well monitored for years, but wasn’t aerated or mixed. They needed help controlling the release of minerals in water, such as manganese and ammonia, for they often reached harmful levels and clogged the distribution network. Health Canada states that “at concentrations greater than 0.15 mg/L, manganese stains plumbing fixtures and fabrics; moreover, in high concentrations, it gives bad taste to water’’. Like iron, it can cause problems in distribution networks by promoting micro-organism overgrowth.

In 2007, we were mandated to provide a complete Bubble Tubing® system with an OctoAir-10 diffuser. Since the installation of the aeration system, recorded data shows a significant decrease in levels of manganese and ammonia in the Saint-Pie’s reservoir. Levels of manganese now rarely exceed the recommended upper limit of 0.15 mg/L.

This improvement was made possible by the effect of dissolved oxygen in the water column. Manganese and ammonia are important indicators of redox potential in sediments, because they become soluble at lower oxygen levels compared to substances like iron and sulphate, which are even more damaging than manganese. In other words, manganese became measurable in the water when the lake ran out of oxygen in its depth, making all harmful molecules at their highest toxicity. Most drinking reservoirs, being highly stratified, go through the same issues in absence of aeration.

Due to the reduction in microbial activity during the winter months, the aeration system was deemed to be less essential and was turned off. However, on December 18, 2009, levels of manganese in the reservoir began to increase, exponentially. The highest level of 0.106 mg/L was reached on December 29, 2009, at which point the aeration system was turned back on. Within 20 hours, the manganese levels returned to the baseline, preventing damage and ensuring the healthy quality of Saint-Pie’s drinking water.

In conclusion, the OctoAir-10 aeration system, using Bubble Tubing® and developed by Products Ltd., significantly reduced manganese and ammonia levels and improved the quality of drinking water in the Town of Saint-Pie. This system has been in operation since 2007 and has saved a lot of money that would have otherwise been necessary for chemical treatments. Interesting fact, the aeration causes another very positive side effect, which was to dramatically reduce the thickness of the accumulated organic sediments (called bio-dredging). The last time the lake was dredged was in 1980 and would have required mechanical dredging in the intervening years. The town has gained many years of extended life since adopting’s technology.

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