Influence of substrates on nutrient removal performance of organic channel barriers in drainage ditches

- OCBs with rice straw (RS) had the highest N removal rates.
- The quantities of RS had significant positive relationship with N removal rate.
- Release of carbon from the RS OCB primarily occurred in the first three weeks.
- RS OCB is a low-cost treatment system for controlling N export from agriculture.

SummaryPilot-scale field trials were performed to investigate the nutrient removal capacity of organic channel barriers (OCBs) with the objective of developing innovative technology for effectively reducing nutrient transport in simulated drainage ditches. The performance comparison of three OCBs, which were composed of rice straw (RS), pine sawdust (PD), and activated carbon with <1 mm quartz sand (AC), indicated that the RS OCBs produced the highest mean removal rate of 73% for ammonium-N (NH4+-N) and 96% for nitrate-N (NO3−-N). Performance of the RS OCBs with RS application rates at 0, 45, 75, and 120 kg dry weight showed the quantity of RS had a significant positive correlation with NH4+-N removal (r = 0.754, p < 0.01) and NO3−-N removal (r = 0.969, p < 0.01), but an insignificant negative correlation with phosphate-P (PO43−-P) removal (r = −0.492, p = 0.104). Release of carbon (C) from the RS OCBs primarily occurred during the first three weeks. Total C loss accounted for less than 5% of the initial C mass. These findings indicated that RS OCBs can be used to construct a low-cost treatment system that requires minimal maintenance and can be easily integrated into drainage ditches to reduce nutrient export from agricultural areas.