Division BAT 7 In order to prevent and reduce the emission of odorous compounds originating from the waste water system, BAT is to use a combination of the techniques given below.
United Kingdom
| Technique | |
|---|---|
| I. Applicable for odours related to water systems closure | |
| a | Design paper mill processes, stock and water storage tanks, pipes and chests in such a way as to avoid prolonged retention times, dead zones or areas with poor mixing in water circuits and related units, in order to avoid uncontrolled deposits and the decay and decomposition of organic and biological matter. |
| b | Use biocides, dispersants or of oxidising agents (e.g. catalytic disinfection with hydrogen peroxide) to control odour and decaying bacteria growth. |
| c | Install internal treatment processes (‘kidneys’) to reduce the concentrations of organic matter and consequently possible odour problems in the white water system. |
| II. Applicable for odours related to waste water treatment and sludge handling, in order to avoid conditions where waste water or sludge becomes anaerobic | |
| a | Implement closed sewer systems with controlled vents, using chemicals in some cases to reduce the formation of and to oxidise hydrogen sulphide in sewer systems. |
| b | Avoid over-aeration in equalisation basins but maintain sufficient mixing. |
| c | Ensure sufficient aeration capacity and mixing properties in aeration tanks; revise the aeration system regularly. |
| d | Guarantee proper operation of secondary clarifier sludge collection and return sludge pumping |
| e | Limit the retention time of sludge in sludge storages by sending the sludge continuously to the dewatering units. |
| f | Avoid the storage of waste water in the spill basin longer than is necessary; keep the spill basin empty. |
| g | If sludge dryers are used, treatment of thermal sludge dryer vent gases by scrubbing and/or bio filtration (such as compost filters). |
| h | Avoid air cooling towers for untreated water effluent by applying plate heat exchangers. |