How the integrated engineering solutions can support the lakes restoration?

Abstract

ABSTRACT A method of the simultaneous reduction of external and internal load of phosphorus as a new solution for lake restoration is presented. A flow-through, stratified lake, with diverse morphometry was selected for the study. In all three parts of the lake, an oxygen deficit was noted at the lake bottom at peak summer stagnation, with a simultaneous increase in mineral forms of phosphorus (the concentration of orthophosphates at sites I, II and III reached 0.301, 0.318 and 0.395 mg P l−1, respectively). Additionally, a large load of nutrients originating from the main inflow (annual load of 14395.9 kg P y−1 and 16 4829.8 kg N y−1), indicates that the conditions present in the lake are conducive to more intensive eutrophication. In this situation, reduction of the main loads of nutrients can be achieved by the simultaneous employment of pipelines delivering oxygenated water to the lake bottom during summer stagnation and a pipeline withdrawing deoxygenated and nutrient-rich water from the bottom in the vicinity of the outflow from the lake. It has been calculated that during the period of summer stagnation (VI-IX), the operation of delivering pipelines can reduce the phosphorus load from the main inflow by 5800.5 kg (40.3%). Using the pipeline withdrawing (site III), the amount of phosphorus removed from the lake would increase by 30.4% (from 2259.6 kg to 3247.8 kg). An additional solution, can be dosing the precipitating substances into the pipes delivering water to the lake, which will enable precise inactivation of phosphorus.