The fate of antibiotics during phosphate recovery processes - A critical review

The principles of circular economy encourage the recovery of phosphorus from nutrient-rich waste streams such as animal manure, domestic wastewater, and urine to supplement existing sources of raw phosphorus. However, these waste streams also contain a wide variety of contaminants of emerging concern including antibiotics, and the recovery of phosphorus from these waste streams results in the co-occurrence of antibiotics with the recovered phosphorus products. This paper provides a comprehensive overview of the fate of environmentally relevant antibiotics in three major existing and upcoming phosphorus recovery processes: precipitation-, membrane-, and adsorption-based treatment. In general, the co-occurrence of antibiotics in recovered phosphorus increases with the presence of dissolved organic matter (DOM) and cations due to π-π interaction and cationic bridge formation, respectively. Additionally, antibiotics display pH-based speciation resulting in electrostatic interactions with recovered phosphorus at pH > 7.0. Furthermore, this critical review establishes a new metric, the relative antibiotic-to‑phosphorus (RAP), defined as the ratio of the concentration of antibiotics to phosphorus in recovered phosphorus to that of the phosphorus-rich waste. Precipitation-based methods, particularly struvite, demonstrated the lowest RAP, while the RAP in carbon-based adsorbents was 1.8 × 10⁸ times higher than in membrane-based processes. In reviewing literature on the fate of antibiotics in phosphorus recovery processes, several research needs are also highlighted: the fate of non-tetracycline antibiotics, simultaneous investigation of phosphorus and antibiotic fate in membrane- and adsorption-based methods, treatment methods to mitigate the co-occurrence of antibiotics in recovered phosphorus product, and the release of antibiotics from recovered phosphate products.