Bio-Bubble Sludge Thickening utilizes aerobic and anaerobic digestion and consolidation on a batch, react and supernatant decant principal. This will achieve the usual requisite of 5 - 7 % Dry Solids thickened sludge (although sludge can be thickened to higher concentrations) but without chemical additives being applied. Sludge is automatically transferred from the Advanced-Aeration basins, which will have already yielded a high-density nutrient rich sludge with extremely low pathogens (see Advanced-Aeration above).

The sludge thickening process of sludge transfer, aeration, anaerobic and quiescent settlement phases followed by supernatant decant will gradually consolidate and increase the dry solids concentration with high efficiency. Moreover, the supplemental aerobic digestion will induce a prolonged period of endogenous decay, which will in turn further reduce the sludge volume.

Where the sludge thickening supernatant liquor is to be returned to the works inlet, it will not exert any additional organic or nutrient load. The aerobic treatment applied will maintain conditions to avert lysis of the micro-organisms within the thickener thus preventing contamination of the supernatant during settlement. Aerobic treatment will also prevent putrefaction so odour control will not be required.

Bio-Bubble Sludge Thickening is capable of producing a sludge that will meet the most stringent standards for disposed to Agricultural Land. It is capable of meeting the conditions as specified under the enhanced treatment of the Safe Sludge Matrix with little or no further treatment. Where biological nutrient removal is applied, the sludge will retain high concentrations of phosphates and can be applied to land as a nutrient rich fertilizer.

The system operates with high efficiency, exceptional reliability and without the sensitivity or complications of anaerobic processes. It is simple to run, requires infrequent operational or maintenance input and will significantly lower overall operational costs in comparison to conventional processes. Bio-Bubble Sludge Thickening now provides a solution for small and medium size works where previously, this was considered to be non-cost effective. It can also be applied to larger scale municipal works.

The main advantages of the process include:
•  Return liquors apply negligible or no surplus loading to the works
•  No odour
•  No chemical additives or dosing plant
•  Simple operation with minimal attention by site operatives
•  Low maintenance and exceptionally long asset life
•  Thickened sludge volumes will be significantly lower than conventional thickening processes: at least 70 % lower.
•  Highly stable sludge containing high levels of nutrient
•  Can be designed for agricultural disposal meeting accordance with ADAS  “Safe Sludge Matrix” enhanced treatment

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