Empirical comparison of activated sludge and high rate algal ponding technologies used to recover water, nitrogen and carbon from brewery effluent

[Display omitted] •High rate algal ponds consume almost two-thirds less energy than activated sludge.•High rate algal ponds produce almost four times more biomass than activated sludge.•Activated sludge converted 66 % of effluent nitrogen into atmospheric nitrogen.•High rate algal ponds converted 25 % of effluent nitrogen into ammonia gas.•High rate algal ponds retained 50 % of effluent nitrogen into biomass. This study assessed the utility of high rate algal ponds (HRAP) as an alternative to conventional activated sludge (AS) for the secondary treatment of anaerobically digested brewery effluent. Both systems treated post-anaerobically digested brewery effluent to a standard suitable for reuse as bottle washing, boiler feed and aquaculture water. The HRAP consumed almost two-thirds less energy (0.11 ± 0.01 kW/m3 of effluent treated) compared to the AS system (0.29 ± 0.11 kW/m3) but produced almost four times more biomass than the AS (317.18 ± 27.76 g/m3 compared to 83.12 ± 64.91 g/m3, respectively). The AS process released 66 % percent of post-anaerobically digested brewery effluent nitrogen into the atmosphere and only retained 8.8 % of it in its biomass, whereas the HRAP released 25 % of that effluent’s nitrogen in a gaseous form and retained 50 % of it in its biomass. The HRAP converted a greater portion of nitrogen from that effluent into biomass, making it more favourable for nitrogen recovery. The major disadvantages of an HRAP is its large land surface area requirement and its raising of pH and conductivity in the treated effluent, rendering it less suitable for irrigation or treatment where a high effluent conductivity is a major concern. Activated sludge systems produce less waste biomass than HRAP and are more suitable for urban situations where space is limited or where land is expensive to acquire.