Effects of Hydrology on Constructed Wetland Vegetation in Tropic Region

Abstract

Toddy distillery units produce a colour effluent which is rich in organic material. This effluent is one of the most environmentally unfriendly industrial product in the Jaffna district of Sri Lanka. Therefore, effluent from distillery unit has to be treated before being discharged into the environment. In this study, experiments were conducted to find out optimum dilution factor of effluent for wetland treatment to remove the organic loads from the effluent in constructed wetlands by using aquatic plants Eichhormia sp, Lemna sp Lemna minor and Pistia sp, The experiments were conducted by different process like aeration, dilution, adjusting the pH by using lime and hydraulic retention time using aquatic plants to reduce the various parameters in effluent. Important chemical properties such as pH, dissolved oxygen, EC and TSS of fresh effluent were measured to identify the problematic parameter and to determine the dilution factor It was found that the dilution of 1, 2, 3, and 4 was not effective due to the lower pH and dissolved oxygen value. The aquatic plants, Eichhormia sp, Lemna sp, and Lemna minor w ere successfully survived in dilution factor of five after aeration and pH adjustment. Pistia sp failed to survive in five dilution. Removal efficiency of phosphate and nitrate were significantly differ in Lemna minor, Lemna and Eicchormia compared from control. Maximum phosphorus removal was in the range of 50-54% and nitrate by 32 to 35% was observed with six days hydraulic retention time. These highest reductions of P 0 43 and N03 were achieved by Lemna minor in the dilution factor of five.