Can phosphorus adsorption clog an alum sludge-based biofiltration system? Evidence and insight

BACKGROUND Aluminium-based drinking water treatment residual (Al-DWTR) has been used as an emergent substrate in laboratory-scale and pilot-scale biofiltration systems (biofilters and constructed wetlands) for its good affinity for phosphorus (P) adsorption. However, there is a concern about whether the P adsorption process will contribute to substrate clogging. Two laboratory-scale up-flow biofiltration systems were set up to identify the contribution of the P adsorption process to clogging under various operation conditions. RESULTS Contributions of individual processes to clogging from biosolids production (S-BS), inert matter generated from the conversion of residual biomass (S-IS), P adsorption (S-P) and inert matter production from influent total suspended solids (S-SS) during operation of the two systems were assessed. After 262 days of operation, results indicated thatS(BS)contributed most (53.16 +/- 7.73%) to the clogging, followed byS(SS)(41.48 +/- 8.02%),S-P(3.14 +/- 0.06%) andS(IS)(2.20 +/- 0.27%) when treating the influent with concentrations of 284-558 mg L(-1)for COD, 54-197 mg L(-1)for SS and 5-13 mg L(-1)for P. CONCLUSIONS The minor contribution of the P adsorption process to substrate clogging further suggests that dewatered Al-DWTR with a high P removal capacity is a promising substrate for use in biofiltration systems. (c) 2020 Society of Chemical Industry (SCI)

Automated summary

Results from two laboratory-scale up-flow biofiltration systems showed that biosolids production (S-BS) contributed the most to clogging, followed by inert matter production from influent total suspended solids (S-SS), with the P adsorption process (S-P) contributing the least. These findings suggest that dewatered Al-DWTR with high P removal capacity is a promising substrate for biofiltration systems.