Greenhouse gas emissions from sludge treatment reed beds

Sludge treatment reed bed systems (STRBs) are considered as an alternative technology for surplus sludge treatment. Organic matter is decomposed by various microbial reactions, resulting in gases such as CO2 and CH4 emitting into the atmosphere. The aim of this study is to investigate gas emission from STRBs. The static transparent chamber was adopted to measure gas emission; it allows sunlight to enter and plants to photosynthesise. The comparison of total solids and volatile solids showed STRBs have a higher efficiency in dewatering and mineralization than a conventional unplanted sludge drying bed (USDB). The CO2 emission ranged from 28.68 to 100.42 g CO2 m(-2) d(-1) in USDB, from 16.48 to 65.18 g CO2 m(-2) d(-1) in STRBs; CH4 emission ranged from 0.26 to 0.99 g CH4 m(-2) d(-1) in USDB, from 0.43 to 1.95 g CH4 m(-2) d(-1) in STRBs. Both gas fluxes decreased towards the end of vegetation and reached the highest rates during the hot and dry summer. After the system was loaded by sludge, the fluxes of CO2 and CH4 significantly decreased in the USDB, whereas they increased in STRBs. In terms of CO2 equivalent, the global warming potential of CH4 was 13.13 g CO(2)eq m(-2) d(-1) and 15.02 g CO(2)eq m(-2) d(-1) in USDB and STRBs, respectively.