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The relationship between operational and bioavailable phosphorus fractions in effluents from advanced nutrient removal systems
Li, B. & Brett, M. T.
Abstract
Because different phosphorus (P) forms vary
greatly in their bioavailability, total phosphorus concentrations
are a problematic predictor of the eutrophication
potential of natural surface waters and wastewater treatment
facility effluents. It is currently not known which
operational P characterizations (i.e., dissolved/particulate
and reactive/non-reactive) best predict effluent P
bioavailability. We characterized the P speciation and directly
measured the bioavailability of P (BAP) using algal
bioassays for 14 full-scale advanced nutrient removal
wastewater treatment plants representing a wide range of P
removal technologies. A strong statistical relationship was
observed between the effluent total BAP (tBAP) and total
reactive P (TRP) (r2 ≈ 0.81), with a tBAP/TRP ratio of
0.61 ± 0.24, indicating that TRP can be used as a conservative
surrogate predictor of tBAP. A comparison of
different operational categories for phosphorus indicated
that sBAP is consistently lower than both soluble P (SP)
and soluble reactive P (SRP) with average ratios of
0.34 ± 0.19 and 0.62 ± 0.27, respectively. This shows a
large fraction of the dissolved non-reactive P (i.e., SPSRP),
and ≥40 % of the P classified as SRP was not
bioavailable. Total BAP concentrations were on average
30 % higher than soluble BAP (sBAP) concentrations,
indicating that the particulate P fraction was an important
component of the BAP for the tested effluents. Comparisons
between different P removal technologies suggest the
bioavailability, and P species composition varies with the
nutrient removal process, and that in many cases, a large
portion (>60 %) of the effluent P is recalcitrant to algal
growth.
Keywords
Phosphorus; Nutrient removal; Bioavailability of phosphorus; Tertiary treatment
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