Using benthos a bioindicator to assess the efficiency constructed wetland community wastewater treatment system

BACKGROUND AND OBJECTIVES: The increasing population and urban growth have led to a higher demand for water in various sectors, resulting in a significant amount of wastewater. Constructed wetlands mimic natural wetlands, using the interaction between plants, soil, and microorganisms to treat wastewater efficiently. This study assesses the diversity, species composition, and distribution of benthic organisms in a community wastewater-filter grass system and explores the relationship between water quality and benthos. METHODS: Water samples were collected from plant plots between December 2021 and March 2022. On-site measurements included temperature, dissolved oxygen, salinity, and pH, whereas laboratory analysis encompassed the biochemical oxygen demand, ammonia, nitrate, total phosphorus, orthophosphate, and suspended solids. Soil samples were taken before and during planting at 2-week intervals, evaluating organic matter, pH, electrical conductivity, salinity, phosphorus, potassium, calcium, magnesium, and plant growth indicators. Benthos sampling involved polyvinyl chloride pipe cores at a depth of 5 cm from the soil surface. Statistical tests were performed to analyze the water quality data. FINDINGS: The study observed a decrease in Chironomid abundance in both constructed wetland systems, indicating their effectiveness in treating wastewater. A comparison of system types revealed that the 5-day detention-2-day dry release system exhibited higher Chironomid abundance than the continuous flow system, and the biological oxygen demand maximum decreasing rate was 95%. The ammonia and nitrate maximum decreasing rates were 97% and 94%, respectively, indicating greater wastewater-treatment efficiency. The study also identified diverse benthic organisms, particularly chironomids, as bioindicators for assessing wastewater conditions. CONCLUSION: The continuous flow system and the 5-day detention-2-day dry release system of constructed wetlands can reduce the organic compounds and increase the oxygen levels in the plant plots. The interaction among plants, soil, and microorganisms is critical in wastewater treatment. In addition, the study highlighted the diversity and abundance of benthic organisms, particularly chironomids, which were more prominent in the continuous flow system. Consequently, the 5-day detention-2-day dry release system was more efficient in treating wastewater than the continuous flow system.