Reconstruction of centre structure, improved settling effect
Secondary clarifiers are the hydraulic bottleneck of the wastewater treatment plant. Even if they are sufficiently large, the sludge very often settles poorly because the central structure in particular is unfavourably designed. In recent years, we have rebuilt several secondary clarifiers with little effort and have achieved significant improvements in the settling effect in all cases.
After redimensioning the central structure and testing the outlet channel, the inlet to the secondary clarifier was moved further down, the inlet gap was redesigned and dimensioned and the retention time in the central structure was increased. Further details such as a correctly dimensioned and positioned flow ring ensure an even and horizontal inflow into the correct density zone.
By stratifying the sludge correctly, the settled sludge is also used as a floc filter and fewer suspended particles enter the clear water outlet.
To ensure that the vertical flow at the edge of the secondary clarifier is not too high, the clear water outlet must also be checked. If it is unfavourably designed, the channel must also be optimised.
By specifically improving the inlet and outlet situation, we have succeeded in significantly improving the throughput and separation performance of the optimised secondary clarifiers. This is also of interest if the phosphorus discharge values need to be reduced. In order to comply with the stricter discharge requirements, good suspended solids retention is required in the secondary clarifier.
