Anaerobic digestion is one of the principal methods used by the water industry to treat primary sewage sludge. It is a preferred process in that it produces methane as a usable by-product, reduces sludge volumes, and creates a digested sludge that is both readily dewaterable and relatively inoffensive in nature.
Efficient breakdown of sludge relies on different groups of bacteria, all of which operate in conjunction, but within a defined range of parameters, e.g. pH, temperature, feed rate, nutrients and trace elements. Periodically however digestion failures occur. This can be due to the presence of inhibitory substances such as high metals concentrations, organic solvents or detergents, or simply from overloading. The result is a failure in part by some of the anaerobic bacteria and a drop in pH. Digester failure may require the digester to be reseeded and more importantly for the pH to be adjusted.
Traditionally lime or sodium carbonate is used for this purpose, but they are powders and can be difficult to apply. Overdosing can often result in the pH increasing to above 12, which will inhibit digester recovery. A recent water treatment plant had similar issues and for health and safety reasons and due to handling difficulties lime was not the preferred alkali for this application. So OMEX Environmental Ltd was contacted for specialist advice on the use of Magmex.
Magmex is a stable suspension which can be easily pumped into a system. More importantly for a biological system Magmex naturally buffers out so that the maximum pH achievable is around 9.5; consequently there is no danger of overdosing.
In this case OMEX were able to deliver the product in a pump off bulk tanker which was then applied straight into the digester. This was achieved with the minimum of disruption, in less than two hours, with only supervisory input from the site. The pH rose to 7.5 within an hour, without the problems associated with lime, and the digester was back online within the day.
As well as Magmex, OMEX provide a wide range of nutrients and neutralisers for biological wastewater treatment and biogas plants. As well as pH control, the company’s range of products are designed to overcome potential problems that can occur with modern effluent and septicity treatment, including odour control, filamentous bulking, and COD removal.
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