Observing the Biologically Induced Phosphate Precipitation by Sludge Extracellular Polymeric Substances in Enhanced Biological Phosphorus Removal

Abstract

Biologically induced phosphate precipitation is a common phenomenon in the enhanced biological phosphorus removal (EBPR) process. In this study, as observed by backscattered scanning electron microscopy coupling energy-dispersive X-ray spectroscopy, large amounts of phosphate precipitates (mainly Ca phosphate) were found to be accumulated in EBPR granular sludge. The Ca phosphate mineral inside EBPR granules was present in two forms: independent mineral clusters and aggregates along with cells packaged by sludge extracellular polymeric substances (EPS). In addition, speciation of phosphorus in EPS extracts was investigated. It was found that about 20.7 ± 2.4% of the EPS-associated phosphorus was found present in a nanosized particulate form by single particle-inductively coupled plasma-mass spectroscopy, and phosphate precipitation induced by isolated EPS was confirmed. Therefore, it was proposed that EPS might play an important role in promoting the phosphate precipitation process through adsorption or entrapment of precipitates to EPS or growth of precipitates inside EPS. Results in this study will be helpful to better understand the phosphorus removal approach through induced precipitation in granular EBPR systems.

Phosphate Recovery Mechanism from Low P-Containing Wastewaters via CaP Crystallization Using Apatite as Seed: Seed Adsorption, Surface-Induced Crystallization, or Ion Clusters Aggregation?

“…The accumulation of a large amount of dense and small fines on the seed surface prompted us to associate P removal with the aggregation of CaP PNCs, the so-called Posner's clusters with sizes between 0.7 and 1.0 nm in the solution [43]. Several documents have reported the aggregation of CaP PNCs [43][44][45].…”

“…The accumulation of a large amount of dense and small fines on the seed surface prompted us to associate P removal with the aggregation of CaP PNCs, the so-called Posner's clusters with sizes between 0.7 and 1.0 nm in the solution [43]. Several documents have reported the aggregation of CaP PNCs [43][44][45]. However, the particle size of fines shown in Figure S4d is about two orders of magnitude larger than that of CaP PNCs, indicating they should not be PNCs themselves.…”

Phosphate Adsorption on Cerium/Terephthalic Acid Metal–Organic Frameworks (Ce‐MOF) Driven by Effective Electrostatic Attraction and Ligand Exchange in a Wide pH Range

“…Therefore, it is impendent to explore efficient technologies to remove phosphates from phosphaterich wastewater. [4] Various approaches have been exploited to remove phosphate, including chemical precipitation, [5] adsorption, [6] electrochemical, [7] biological treatment, [8] etc. Among them, adsorption is regarded as the most efficient and feasible route because of its easy operation, low power consumption, less secondary pollution and high efficiency at trace level wastewater.…”