Chemical dosing solves odour problems in municipal waste water

OdourPro on 9 January 2018

Municipal waste water consists of domestic, commercial and industrial waste water streams. A network of sewers and pump stations collects these streams and discharges them to waste water treatment plants. As cities and manufacturing centres expand, municipal networks must deal with higher volumes of waste water. The septic nature of waste water creates challenges for municipal councils.

OdourPro supplies municipal waste water solutions and services to improve odours. Contact us to find out more.

Key challenges of municipal waste water management

Municipal waste water is septic because there are bacteria feeding on the waste. Without any chemical dosing intervention, the activity of bacteria in waste water streams produces H2S gas. This H2S creates challenges for municipal waste water operators in the following ways:

  1. H2S is hazardous to humans. Peak H2S concentration in a manhole of a waste water sewer system has been known to reach as high as 500 ppm. At these levels, people experience loss of consciousness and breathing difficulty. Continuous exposure for more than 30 minutes can even result in death. Controlling H2S production from waste water protects municipal workers from occupational health hazards.

  2. H2S leads to corrosion of piping and equipment, which accelerates when H2S forms sulphuric acid in the waste stream. Corrosion causes a loss of metal thickness in piping. This requires premature replacement and the risk of sewerage leaks into the groundwater. It is important to control H2S production in waste water to prevent high maintenance and replacement costs due to corrosion.

  3. H2S gas smells terrible. It is noticeable to humans at very low levels of below 1.5 ppm. The rotten egg odour of H2S is a primary cause of complaints from residents surrounding sewer manholes and pump stations. In this age of increased environmental awareness and pressure, municipalities must work hard to keep positive relationships with surrounding residents. To do this, the challenge of H2S production must be overcome.

Chemical dosing systems for municipal waste water

Chemical dosing systems act on the source of odours rather than the symptoms. They do not mask the effects of odours, but rather eliminate their cause. They prevent the formation of H2S in waste water streams.

There are three main chemical dosing options to reduce the formation of H2S. OdourPro experts can help you determine the most suitable solution for your application:
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  • Ferrous Chloride dosing systems prevent the formation of H2S. The iron reacts with sulphides in the waste water to form Iron Sulphide. This white product precipitates out of solution and plays no further part in chemical and biological reactions. Ferrous Chloride is a hazardous substance. Strict protocols surround the handling and use of this material.

  • Magnesium hydroxide raises the pH of waste water to approximately 8.5. This pH level inhibits the biological reactions that cause the production of H2S. Once the effluent reaches the target pH, adding more Magnesium Hydroxide has no effect.

  • Calcium Nitrate provides an alternative source of oxygen for bacteria. They feed on the nitrates rather than sulphates, therefore preventing the chain of reactions that result in H2S production.

Implementing a chemical dosing system is the first step to manage H2S production and overcome the challenges it causes. However, monitoring and planned maintenance of dosing systems enhance their effectiveness and reduce long term costs.

OdourPro provides liquid sampling and H2S gas data logging. From this information, chemical dosing can be optimised and costs reduced. Regular maintenance of chemical dosing systems prevents line blockages and pump seal failures.

Case studies

Central Coast Council is a new council that inherited pre-existing odour issues at their Kincumber Waste Water Treatment Plant. The combination of the large collection network, multiple pump stations and rising mains as well as the accumulation of diverse streams of waste was producing H2S. OdourPro implemented targeted dosing of Ferrous Chloride. The system is flow paced to optimise chemical use. Automation systems with remote monitoring ensure up to date information is available.

Hunter Water experienced high H2S levels and odour issues at the Dora Creek Waste Water Treatment Plant. They implemented a Ferrous Chloride dosing solution from OdourPro and achieved a 95% reduction in both H2S production and odour complaints.

OdourPro has extensive experience in municipal waste water management. We have access to a range of technologies so that we can apply the most effective solution to your site.

Find out more about municipal waste water management here or call our expert team on 1800 510 704 today to arrange a consultation to help you design and implement a chemical dosing system.