DefinePK

Abstract

This study aims to determine the self-purification of Lake Maninjau based on the depth stratification. Sampling was carried out at the locations where there was lake water use, namely in the middle, domestically, in the hydropower area, in the endemic fisheries and at the aquaculture cages under SNI 6989.57: 2008. The measured parameters were BOD and the environmental parameters of pH, DO, and temperature were used to determine the lake stratification. Lake Maninjau's self-purification was determined by comparing the deoxygenation (K1) and reaeration (K2) coefficients. Based on the pH, DO, and temperature profiles, the epilimnion layer was found at 0-22 m depth and the hypolimnion layer started at a depth of 22 m. The BOD concentrations obtained did not meet the Government Regulation quality standards of 21.87-47 mg/L. The deoxygenation coefficient K1 in the epilimnion layer ranged from 0.04-1.49/day while in the hypolimnion layer it ranged from 0.08-0.54/day. The reaeration coefficient K2 in the epilimnion layer ranged from 0.04 to 0.57/day while in the hypolimnion layer, it ranged from 0.005 to 0.04/day. Wind speed and depth play a significant role in determining the lake’s self-purification capacity. The self-purification of the lake was still held mainly in the epilimnion layer at depths of 0-9 m while in the hypolimnion layer deeper than 22 m, its ability begins to diminish. This indicates that most of the lake waters have a significantly decreased natural self-purification capacity.