Slow growers possess a high pollutant removal potential through granule formation for wastewater treatment

For the upgradation and building of wastewater treatment plants in limited areas, biological wastewater treatment processes with a high pollutant removal loading rate are required. Biofilm or membrane-based systems can achieve a high pollutant removal loading rate through high microbial biomass concentrations and/or activities. The sludge separation is the primary bottleneck for achieving high biomass concentrations inside the biological reactors. In addition, low growers including anaerobic ammonia oxidation bacteria and methanogens are usually easier to form granules and induce high nutrient removal loading rates. The possible granule formation mechanisms should be clarified through physical, chemical and biological aspects, including hydraulic control, microbial extracellular polymeric substances formation, biological energy utilization control, microbial interactions and also other microbial processes. In future, the possible mechanisms should be further clarified, and then high-efficient bioreactors, new microbial ecology control strategy and novel biofilm carriers should be developed for advancing biological wastewater treatment processes with high pollutant removal loading rates.