Treatability and fate of various phosphorus fractions in different wastewater treatment processes

摘要

The increasingly more stringent phosphorus (P) discharge limits, which are below thenconcentrations reliably achievable with currently available technologies, demand for betternunderstanding of phosphorus removal mechanisms. This study investigated the compositionalnfractions of phosphorus (P) in various effluents as well as the efficacy of different levels ofntreatment processes for removing different fractions of P in wastewater. The results showed thatnBNR can effectively remove most fractions of P, with relatively higher efficiencies (493%) towardsnbioavailable forms of P including soluble reactive P (sRP), particulate reactive P (pRP) portion andnparticulate acid hydrolysable P (pAHP) and, it showed relatively lower efficiency (78%) towardsnorganic P. Soluble acid hydrolysable P (sAHP) was not effectively removed (o40%). Chemical Pnremoval process was more effective for elimination of sRP, sAHP and particulate organic P (pOP),nbut was not as effective for removing pAHP and, it exhibited nearly no removal of dissolvednorganic P (DOP). We found that chemical P removal process led to a significant increase in thenconcentration of pRP by up to 255%, indicating that these pRP (presumably as chemically boundednP) are likely formed through chemical precipitation/co-adsorption. Only 22% and 64% of the pRPnwas removed through tertiary clarifier and filtration, respectively. This implies that chemicalnaddition converts sRP into particulate-associated P, mostly as pRP that was not easily removed bynsedimentation and filtration, therefore, the efficacy of chemical P removal highly depends on theneffectiveness of solid and liquid separation process. As more sRP and particulate P were removednthrough the series of treatment processes, the percentage contribution from organic P increasesnwith the level of treatment due to its recalcitrant nature. Our results indicated that in order tonachieve extremely low effluent P levels, technologies and processes that can enhance pRP andnDOP removal will be required.