Removal of Heavy Metals and Bulk Organics towards Application in Modified Constructed Wetlands Using Activated Carbon and Zeolites

Abstract

Constructed wetlands are a versatile technology for various treatment approaches, especially in emerging countries. The research aims to study and optimize the hybridizing process of a vertical subsurface flow constructed wetland with adsorption technology to provide energy-efficient and sustainable removal of heavy metals and bulk organics before their discharge into water bodies or water reuse for irrigation. This study focuses on the adsorption of selected heavy metals present in sewage from Kanpur, India, a cluster of tanning industries and other relevant industrial polluters, investigating the pollutant adsorption onto activated carbon and zeolites in batch and column tests. The results of the batch tests indicated high zeolite loading rates for lead (91.6 mg/g), chromium (60.8 mg/g) and copper (47.4 mg/g). In the column tests applying different adsorbent combinations and ratios, the average removal rates were as follows: 54.6% for cadmium, 14.1% for chromium, 52.4% for copper, 2.2% for iron, 29.2% for manganese, 26.6% for nickel, 35.2% for lead and 44.6% for zinc. The column tests conducted in preparation for field testing in pilot wetlands showed that shorter retention times and background bulk organic concentrations, as well as high ammonium concentrations, negatively affected heavy metal removal by reducing the adsorption and ion exchange capacity of the adsorbents.