Estimation of Nutrient Elution and Removal on Sediment Surface of Clayey Canal Based on Hydraulic Model Experiments

Abstract

A clayey canal tends to be selected over a concrete-lined canal to achieve water quality conservation in a land improvement project. Therefore, it is important to analyze quantitatively the interaction of nutrients on the sediment in a clayey canal. In this paper, the COD, nitrogen and phosphorus fluxes as well as elution and removal rates across/on the sediment surface were estimated based on hydraulic models experiments. The experiments were carried out for water under aerobic conditions at 30-32°C (CASE 1) and 6-9°C (CASE 2). In CASE 1, the net COD elution rate and the net phosphorus elution rate were 8.2 mg.m - 2 .day - 1 and 11.5 mg.m - 2 .day - 1 , respectively. Nitrogen was removed by nitrification on the sediment surface so that the net removal rate which is composed of the denitrification rate, the settling rate and the elution rate was 15.1 mg.m - 2 .day - 1 . The rate constant in which the nitrogen removal is expressed as a first-order kinetic was 0.010 m/day. In CASE 2, the net COD elution rate and the net phosphorus elution rate were 9.9 mg.m - 2 .day - 1 and 5.4 mg.m - 2 .day - 1 , respectively. The net nitrogen removal rate and its rate constant were 9.0 mg.m - 2 .day - 1 and 0.0023 m/day, respectively. The rates of elution and removal increased remarkably with the temperature.