The present invention relates to a vertically adjustable screened decanter system to replace prior art stationary or pivoting effluent weirs in water clarifiers and settling basins. The screened decanter has no physical weir and relies instead on maintaining a desired flow rate by controllably varying the depth of immersion of a screened box. The decanter is periodically raised into a hood that provides spray cleaning and disinfection of the screened box. The system is capable of removing up to 85% of the BOD in a wastewater stream.