Constructed Wetland as an Alternative to Conventional Industrial Wastewater Treatment to Promote Carbon Sequestration for Sustainable Future

Constructed wetlands (CW) are man-made systems that mimic the natural wetlands. They can be used for various purposes, including wastewater treatment, stormwater management, and carbon sequestration. Wetlands naturally absorb and store carbon from the atmosphere, and CW can replicate this process by using plants and microorganisms to remove and store carbon from the water. Conventional wastewater treatment plants (WWTP) use more energy and contribute to carbon emissions, so many industries are looking for ways to reduce greenhouse gas (GHG) emissions. While CW have been widely used for municipal and sewage treatment, their use as an alternative or supplement to industrial wastewater treatment, particularly in the oil and gas and petrochemical industries, is limited. However, CW have the potential to promote carbon sequestration and have a lower cost of capital and operating expenses compared to conventional WWTP, while also emitting lower GHG emissions. A case study is presented for two types of system in which one is actual operating conventional WWTP in Malaysia design and operate at 60m3/d and a hybrid CW of equivalent treatment capability and capacity. The case study found that GHG emissions from a conventional WWTP were approximately 3.75 times higher than the hybrid CW system with the same treatment capacity. For a small capacity WWTP at 60m3 per day, converting the treatment system from conventional WWTP to CW will reduce approximately 45.7t CO2 eq per year based on Life Cycle Assessment (LCA) calculation. The conventional WWTP consumed much higher power especially from the air blower compared to CW where limited number of equipment is required. The additional carbon sink for CW from carbon sequestration from plant, soil decomposition and sediment has not been quantified in the LCA calculation. Hence, it is expected the actual CO2 eq emission for CW is much lesser than the conventional WWTP. With all the benefit identified and the proven success case in several places, the adoption of CW as an industrial WWTP should be widely promoted as the replacement of conventional WWTP for sustainable future.