Role of algal biofilm in improving the performance of free surface, up-flow constructed wetland

• First-ever-study reporting role of algal biofilm in enhancing performance of CW.
• The biofilm enhanced pollutant removal was in the order of phosphates > ammonia > COD.
• Biofilm significantly improved phosphate removal.
• Ammonia removal improved in presence of biofilm, higher temperature and longer HRT.
• COD removal during winter season was compensated by biofilm.

The role of algal biofilm in a pilot-scale, free-surface, up-flow constructed wetland (CW), was studied for its effect on chemical oxygen demand (COD), ammonia and phosphate removal during three seasons-autumn, winter and early spring. Effect of hydraulic retention time (HRT) was also investigated in presence and absence of algal biofilm. Principal Component Analysis was used to identify the independent factors governing the performance of CW. The study showed algal biofilm significantly improved nutrient removal, especially phosphate. Ammonia removal varied with HRT, biofilm and ambient temperature. Increase in biofilm thickness affected ammonia removal efficiency adversely. Algal biofilm-assisted COD removal compensated for reduced macrophyte density during winter. Two-way ANOVA test and the coefficients of dependent factors derived through multiple linear regression model confirmed role of algal biofilm in improving nutrient removal in CW. The study suggests that algal biofilm can be a green solution for bio-augmenting COD and nutrient removal in CW.

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