ABSTRACT
Most recent advances for phosphorus (P) recovery using brewery yeast on laboratory scale were used to scale up to a pilot-scale process (BioP-Rec module) and applied in a full-scale wastewater treatment plant (WWTP). A P balance was established for WWTP Markranstädt according to two thresholds: (1) the economic feasibility threshold for P recovery of 0.05 kg/m3 of free P, and (2) the German Sewage Sludge Ordinance (GSSO) threshold, which demands that all WWTPs with a P content in dry matter (DM) of biosolids of 20 gP/kgDM or higher in the coming years must perform mandatory P recovery. In terms of defined thresholds, return and excess sludges were identified as the most feasible WWTP process streams for P recovery. In a 1 m3 BioP-Rec module a 3 stage process was established. From the P-rich water-phase of the return sludge produced in stage 1, which contained 0.051 kg/m3 of free P, 77.56% was taken up by P-depleted brewer's yeast Saccharomyces pastorianus in 3 h in stage 2. In stage 3, the yeast was concentrated in 1 h to produce yeast sludge as a fertilizer product. We demonstrated a novel pilot-scale process for the production of bio-based P-rich fertilizer.
ABSTRACT
Phosphorus (P) is a non-renewable resource and is on the European Union's list of critical raw materials. It is predicted that the P consumption peak will occur in the next 10 to 20 years. Therefore, there is an urgent need to find accessible sources in the immediate environment, such as soil, and to use alternative resources of P such as waste streams. While enormous progress has been made in chemical P recovery technologies, most biological technologies for P recovery are still in the developmental stage and are not reaching industrial application. Nevertheless, biological P recovery could offer good solutions as these technologies can return P to the human P cycle in an environmentally friendly way. This mini-review provides an overview of the latest approaches to make P available in soil and to recover P from plant residues, animal and human waste streams by exploiting the universal trait of P accumulation and P turnover in microorganisms and plants.
ABSTRACT
Phosphorus (P) in wastewater has a variety of negative effects and is usually permanently lost as a non-renewable resource. To mitigate future P shortage, P must be recovered from wastewater, preferably by bio-based technologies to avoid toxic side streams. A standardized procedure for the determination of P types and P concentrations in all liquid and solid process stages was established, which is applicable to all full-scale wastewater treatment plants (WWTPs). Based on this, an equally universal calculation framework for P-cycle assessment based on volume flow and mass load rates was designed to identify the most promising process streams for biological P recovery. As an example, in 16 process streams of a typical WWTP, concentrations of free, bound and total P were calculated and microbial communities were analyzed by flow cytometry over 748â¯days. The most promising process streams for the recovery of free P were anaerobic digester sludge, centrate and the water-extracts of the biosolids with 0.510â¯kg P m-3, 0.075â¯kg P m-3 and 1.023â¯kg P m-3, while the best process streams for the recovery of bound P were return sludge, excess sludge, anaerobic digester sludge, and the solids of the biosolids with 0.300â¯kg P m-3, 0.268â¯kg P m-3, 0.213â¯kg P m-3 and 1.336â¯kg P m-3, respectively. Microorganisms capable of P accumulation were active in all process stages and it was observed that chemical P precipitation antagonizes biological P removal. The framework for P-cycle assessment was able to identify process streams that are economically viable to make future in-stream technologies for biological P removal feasible.
