Feasibility of iron scraps for enhancing nitrification of domestic wastewater at low temperatures

The development of an effective approach to improve low-temperature nitrification of domestic wastewater remains an important issue that needs to be urgently addressed. This study was intended to verify the feasibility of using iron scraps as an effective immobilization material to enhance nitrification activity in domestic wastewater-treatment systems at low temperatures. Iron scraps were tried and compared with one common immobilization material (PVA-SA embedded balls) in terms of low-temperature nitrification performances, anti-shock capacity, dynamics of microbial community, and economic costs. The results showed that compared with control, the average nitrification efficiency of iron scraps and PVA-SA embedded balls increased separately by 15.7% and 27.6% at low temperatures. Among these groups, the iron scrap-based group demonstrated the best anti-shock capacity and the smallest fluctuation (lower than 10%) with the shortening of HRT (hydraulic retention time) or the increase of inlet ammonium level. Nitrosomonas was found to be the dominant bacterial genera for these two immobilization materials. The increased costs of iron scraps and PVA-SA embedded balls were about yen 0.03 and yen 0.78 per ton of treated domestic wastewater. Taken together, iron scraps have some significant advantages including low costs, easy availability, and good anti-shock capacity, which make them a promising candidate for enhanced nitrification of domestic wastewater at low temperatures.

Automated summary

Iron scraps were found to increase nitrification efficiency at low temperatures by 15.7%, compared with the PVA-SA embedded balls by 27.6%. Among these groups, the iron scrap-based group demonstrated the best anti-shock capacity with minimal fluctuations under changing conditions. Nitrosomonas was identified as the dominant bacterial genus for both immobilization materials. The additional costs of iron scraps and PVA-SA embedded balls were found to be minimal per ton of treated domestic wastewater. In conclusion, iron scraps offer significant advantages in terms of low costs, availability, and anti-shock capacity, making them a promising candidate for enhancing nitrification of domestic wastewater at low temperatures.