Reduction In Phosphorus Concentration Research Articles

Phosphorus recovery from calcium phosphate enriched activated sludge

This study explores the potential of activated sludge from wastewater treatment plants (WWTP) as an alternative source of phosphorus, vital for fertilisers and other products, compared to large-scale phosphorus mining. The research focuses on analysing optimal conditions and the impact of activated sludge characteristics on phosphorus release from calcium phosphate compounds, particularly hydroxyapatite (HAP). Using batch reactor experiments with varying pH and contact time, the results reveal that lower pH values, particularly pH 4, result in higher phosphorus release. The study also finds that calcium, the predominant metal content in activated sludge, plays a vital role in bonding with phosphates and forming new compounds, effectively reducing phosphorus concentration in the solution. Moreover, the VSS/TSS value in the activated sludge has no significant effect on phosphorus release, but interventions occur at high VSS/TSS values. The reaction rate coefficient is calculated at 0.00033/min at pH 4. Overall, this research emphasises the potential of phosphorus recovery from calcium phosphate enriched activated sludge and underscores the importance of optimising pH and considering activated sludge characteristics for efficient phosphorus release.

The role of bioturbation triggered by benthic macroinvertebrates in the effectiveness of the Floc & Lock technique in mitigating eutrophication

Anthropogenic activities have led to excessive loading of phosphorus and nitrogen into water bodies, leading to eutrophication and promoting the growth of cyanobacteria, posing a threat to the health of humans and aquatic animals. Techniques such as Floc & Lock have been developed to mitigate eutrophication by reducing phosphorus concentrations in water and preventing algal blooms. However, little attention has been given to the impact of phosphorus resuspension by sediment-associated organisms such as benthic macroinvertebrates, on the effectiveness of this technique. Here, we experimentally evaluated whether the presence of snails Melanoides tuberculata (Müller, 1774) and larvae of Chironomus sancticaroli (Strixino and Strixino, 1981) affects the efficiency of the Floc & Lock technique. Snails and chironomid larvae are benthic macroinvertebrates commonly found in high abundance in eutrophic reservoirs. Specifically, we tested the hypotheses that (i) the presence of benthic macroinvertebrates reduces the efficiency of coagulants and clays in removing phosphorus and algal biomass from the water column, and (ii) this effect is species-dependent, as some organisms such as the snails, revolve the substrate and resuspend sedimented particles, while other ones, such as chironomid larvae, aid in the removal of phosphorus from the water column by depositing them in the sediment. Our findings revealed that the impact of benthic macroinvertebrates on the effectiveness of the Floc & Lock technique is species-dependent. Chironomid larvae positively influenced the efficiency of the technique by aiding in the removal of total phosphorus, soluble reactive phosphorus, and algal biomass from the water column, depositing them in the sediment. In contrast, the presence of snails had the opposite effect, resulting in increased phosphorus concentration and algal biomass in the water. Surprisingly, the snails consumed the flocs formed by the coagulant and clay within a short time interval of 72 h, raising concerns due to the presence of toxic cyanobacterial biomass in these flocs. Our study emphasizes the importance of considering benthic macroinvertebrates and their impact on the effectiveness of eutrophication management techniques.

Phosphorus Removal in VFCWs with Lightweight Aggregates Made of Fly Ash from Sewage-Sludge Thermal Treatment (FASSTT LWA)

This study analyzed the effect of lightweight aggregates made of fly ash from sewage-sludge thermal treatment (FASSTT LWA) on the effectiveness of phosphorus removal from wastewater in vertical constructed wetlands (CWs), depending on FASSTT LWA content in the CW filling and hydraulic loading rate. It was performed over 13 weeks using 15 lysimeters prepared as double-layer systems. An upper layer was made of FASSTT LWA above the gravel layer with different thicknesses of FASSTT LWA (CW 0 cm: only gravel; CW 12 cm, CW 25 cm; CW 50 cm, and CW 100 cm: only FASSTT LWA). Each filling variant was repeated three times. Wastewater with a mean phosphorus concentration of 7.43 mgP/L was fed to the lysimeters once a day. The hydraulic loading rates tested were 3.0, 5.0, and 7.0 mm/d. Both the increased FASSTT LWA content in the CW filling and the decreasing hydraulic loading rate were found to boost the effectiveness of phosphorus removal in the treated wastewater. Constructed wetland filled in 100 % with FASSTT LWA ensured a reduction in phosphorus concentration below 2.0 mg P/L at all hydraulic loading rates tested.

Watershed- and reach-scale drivers of phosphorus retention and release by streambed sediment in a western Lake Erie watershed during summer

Reducing phosphorus (P) concentrations in aquatic ecosystems, is necessary to improve water quality and reduce the occurrence of harmful cyanobacterial algal blooms. Managing P reduction requires information on the role rivers play in P transport from land to downstream water bodies, but we have a poor understanding of when and where river systems are P sources or sinks. During the summers of 2019 and 2021, we sampled streambed sediment at 78 sites throughout the Maumee River network (a major source of P loads to Lake Erie) focusing on the zero equilibrium P concentration (EPC0), the soluble reactive phosphorus (SRP) concentration at which sediment neither sorbs nor desorbs P. We used structural equation modeling to identify direct and indirect drivers of EPC0. Stream sediment was a P sink at 40 % and 67 % of sites in 2019 and 2021, respectively. During both years, spatial variation in EPC0 was shaped by stream water SRP concentrations, sediment P saturation, and sediment physicochemical characteristics. In turn, SRP concentrations and sediment P saturation (PSR) were influenced by agricultural land use and stream size. Effect of stream size differed among years with stream size having a greater effect on SRP in 2019 and on PSR in 2021. Streambed sediment is currently a net P sink across the sites sampled in the Maumee River network during summer, but sediment at these locations, especially sites in headwater streams, may become a P source if stream water SRP concentrations decrease. Our results improve the understanding of watershed- and reach-scale controls on EPC0 but also indicate the need for further research on how changes in SRP concentration as a result of conservation management implementation influences the role of streambed sediment in P transport to Lake Erie.

Dispersed Urban‐Stormwater Control Improved Stream Water Quality in a Catchment‐Scale Experiment

AbstractTraditional urban drainage degrades receiving waters. Alternative approaches have potential to protect downstream waters, but widespread adoption requires robust demonstration of their feasibility and effectiveness. We conducted a catchment‐scale experiment over 19 years to assess the effect of dispersed stormwater control measures (SCMs), measured as a reduction in effective imperviousness (EI) on stream water quality in six sites on two streams. We compared changes in those sites over 7 years as EI decreased, to changes in the 12 preceding years, and in three reference and two control streams. SCMs reduced phosphorus concentrations and summer temperature to reference levels in dry weather where EI was sufficiently reduced, but effects were smaller with increased antecedent rain. SCMs also reduced nitrogen concentrations which were influenced by septic tank seepage in all sites. SCMs had no effect on suspended solids concentrations, which were lower in urban than in reference streams. SCMs increased electrical conductivity: along with reduced temperature this is evidence of increased contribution of groundwater to baseflows. This experiment strengthens inference that urban stormwater drainage increases contaminant concentrations in streams, and demonstrates that such impacts are reversible and likely preventable. Variation in degree of water quality improvement among experimental sites suggests that achieving reference water quality would require SCMs with large retention capacity intercepting runoff from nearly all impervious surfaces, thus requiring more downslope space and water demand. EI is a useful metric for predicting stream water quality responses to SCMs, allowing better catchment prioritization and SCM design standards for stream protection.

Phosphorus removal by aquatic vegetation in shallow eutrophic lakes: a laboratory study.

Eutrophication in inland lakes is occurring frequently with the rapid urbanization, the increases in human population, and the intensive agricultural activities. Traditional management programs focusing on external nutrient reduction failed in recovery of certain aquatic environments where internal nutrient releases are substantial. In this study, we evaluated the effects of aquatic vegetation in altering the phosphorus concentrations in a shallow, eutrophic lake through laboratory flume experiments. Our measurements demonstrated that aquatic vegetation could effectively lower the phosphorus levels in the water column, and the average reduction reached 90% for submerged vegetation and 80% for emergent vegetation. The experimental results showed that the submerged vegetation was effective to reduce phosphorus concentrations in the top and mid layers of pore waters and sediments. Differently, the emergent vegetation would assimilate more phosphorus in the bottom layer due to its deep root distributions. The flowing-water environment favored phosphorus removal for emergent vegetation, while the submerged vegetation was more functional in static waters according to our observations. The flux results showed that phosphorus transports from water columns to leaves, roots to leaves, and sediments to roots were all inhibited in flowing-water environments for submerged vegetation. Oppositely, the fluxes of emergent vegetation groups were all enhanced in flowing waters. Our experiments could inform ecosystem management concerning the potentials of aquatic vegetation in nutrient removal at regional and lake-wide scales.

Single-stage or two-stages bio-electrochemical treatment process of drainage from soilless tomato cultivation with alternating current

This work substantially extends knowledge on the possibilities of treating drainage from full-technical scale soilless tomato cultivation. Experiments were carried out in one stage bio-electrochemical reactor and separate biological and electrochemical reactors connected in series, with using alternating current. The study aimed to determine: the effect of single-stage, two-stages wastewater treatment process and hydraulic retention time (HRT) on the effectiveness of contaminant removal and organic substrate consumption, the contribution of biological and electrochemical processes and on the kinetics of contaminant removal. The use of coupled biological and electrochemical processes in one reactor (R1) showed the highest efficiency nitrogen removal, reaching 62.7 % (HRT = 1d) and 89.8 % (HRT = 7d), respectively. The separation of biological (R2-I) and electrochemical processes (R2-II) demonstrated the first one (R2-I) to be mainly responsible for denitrification (TN removal effectiveness at 51.9 % compared to 54.9 % effectiveness of the whole system). In single R1, the concentration of phosphorus in the effluent reached 2.32 ± 0.47 mg P∙L−1 (97.1 %; HRT = 1d) and 1.16 ± 0.06 mg P∙L−1 (98.3 %; HRT = 7d). In R2 enabled reducing phosphorus concentration in the effluent to 0.18 ± 0.07 mg P∙L−1 (99.8 %). The study showed that using of alternating current proved viable in increasing the rate and effectiveness of denitrification, but only if we apply electric current simultaneously with external source of organic carbon.

The role of activated carbon nanoparticles on hydro-degumming non-edible vegetable oils

This study aims to assess the role of activated carbon nanoparticles in hydro-degumming non-edible vegetable oils. Bamboo Activated Carbon Nanoparticles (BAC-NPs) is added to oils in degumming process. Characterizations revealed mesoporous structures with specific surface area 673.298 m2/g, positive surface charge, aromatic ring cluster, and increased hydrophilicity. Magnetic moment induced by delocalized electrons in aromatic ring cluster of BAC-NPs works towards paramagnetic negatively charged oxygen around the phosphate head group of phospholipid molecule. It also works towards water molecules, changes water proton spin isomer from para to ortho, decreases intramolecular energy in water, facilitates base-promoted ester hydrolysis reaction. These phenomena, combined with heat energy and centrifugation force, trigger bonds disruption within phospholipid molecule, lead to a higher probability of phosphate head group detachment off the phospholipid molecule. As a result, there is a large reduction in phosphorus concentration (around 95%) and a slight improvement in viscosity and calorific value in treated oils.

Facile synthesis of novel tremella-like Mn0@Mn2O3 and its exceptional performance on removal of phosphate

Phosphorus is an essential nutrient for biological growth, but its excessive presence in water can lead to eutrophication. Reducing phosphorus concentrations is an important way to prevent eutrophication of surface water bodies. In this study, a novel zero-valent manganese (ZVM) Mn0@Mn2O3 sorbent was synthesized via a facile one-step reduction method at ambient temperature. The morphology and surface properties of the Mn0@Mn2O3 were analyzed by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Zeta potential analyzer, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The obtained amorphous sample consists of many small tremella-like particles. The as-prepared sorbent shows exceptional phosphate removal performance and has a maximum adsorption capacity of 113.7 mg-P/g at pH 7.0, superior to many reported adsorbents. The removal of phosphate is obviously pH-dependent and is favorable under near-neutral and weak-alkaline conditions (pH 6.5–8.5). The kinetics data fit well to the pseudo-second-order model. The coexisting SO42-, CO32- and Cl- have no great influence on phosphate sorption, whereas, the SiO32- shows negative effect at high concentration. The sorbent is effective for phosphate removal from real municipal wastewater. The results of ionic strength effect experiment, SEM, XRD, FTIR and XPS analyses reveal that the phosphate was mainly removed through surface precipitation and formation of inner-sphere surface complexes. The Mn0@Mn2O3 is a promising sorbent for phosphate removal from surface water and wastewater, owning to its exceptional performance, high selectivity, environmental friendliness and easy preparation.

Experimental and Techno-Economic Study on the Use of Microalgae for Paper Industry Effluents Remediation

Humanity is facing some major global threats, namely lack of environmental sustainability, the energy crisis associated with the unsustainable reliance on fossil fuels, and water scarcity, which will be exacerbated with the rapid growth of urban areas. Researchers have drawn their attention to microalgae, photosynthetic microorganisms known for their environmental applications, such as wastewater remediation and lipids accumulation, to produce third-generation biofuels to solve some of these major issues. Considering this dual role, this study evaluated the potential of the microalga Chlorella vulgaris on nutrient removal from a paper industry effluent and bioenergy production. Firstly, experiments were performed to assess the potential of this microalga to: (i) successfully grow in different concentrations of a paper industry effluent (20% to 100%); and (ii) treat the industrial effluent, reducing phosphorus concentrations to values below the accepted legal limits. Then, a techno-economic assessment was performed to study the viability of a C. vulgaris biorefinery targeting the remediation of a paper industry effluent and bioenergy production. The results have shown that C. vulgaris was able to successfully grow and treat the paper industry effluent. Under these conditions, average biomass productivities determined for this microalga ranged between 15.5 ± 0.5 and 26 ± 1 mg dry weight (DW) L−1 d−1, with maximum biomass concentrations reaching values between 337 ± 9 and 495 ± 25 mg DW L−1 d−1. Moreover, final phosphorus concentrations ranged between 0.12 ± 0.01 and 0.5 ± 0.3 mg P L−1, values below the legal limits imposed by the Portuguese Environment Agency on the paper industry. Regarding the proposal of a microalgal biorefinery for the bioremediation of paper industry effluents with bioenergy production, the techno-economic study demonstrated that six of the seven studied scenarios resulted in an economically-viable infrastructure. The highest net present value (15.4 million euros) and lowest discounted payback period (13 years) were determined for Scenario 3, which assumed a photosynthetic efficiency of 3%, a lipids extraction efficiency of 75%, and an anaerobic digestion efficiency of 45%. Therefore, it was possible to conclude that besides being economically viable, the proposed biorefinery presents several environmental benefits: (i) the remediation of an industrial effluent; (ii) CO2 uptake for microalgal growth, which contributes to a reduction in greenhouse gases emissions; (iii) production of clean and renewable energy; (iv) soil regeneration; and (v) promotion of a circular economy.

Biofouling control by phosphorus limitation strongly depends on the assimilable organic carbon concentration

Nutrient limitation is a biofouling control strategy in reverse osmosis (RO) membrane systems. In seawater, the assimilable organic carbon content available for bacterial growth ranges from about 50 to 400 μg C·L−1, while the phosphorus concentration ranges from 3 to 11 μg P·L−1. Several studies monitored biofouling development, limiting either carbon or phosphorus. The effect of carbon to phosphorus ratio and the restriction of both nutrients on membrane system performance have not yet been investigated.This study examines the impact of reduced phosphorus concentration (from 25 μg P·L−1 and 3 μg P·L−1, to a low concentration of ≤0.3 μg P·L−1), combined with two different carbon concentrations (250 C L−1 and 30 μg C·L−1), on biofilm development in an RO system. Feed channel pressure drop was measured to determine the effect of the developed biofilm on system performance. The morphology of the accumulated biomass for both carbon concentrations was characterized by optical coherence tomography (OCT) and the biomass amount and composition was quantified by measuring total organic carbon (TOC), adenosine triphosphate (ATP), total cell counts (TCC), and extracellular polymeric substances (EPS) concentration for the developed biofilms under phosphorus restricted (P-restricted) and dosed (P-dosed) conditions.For both carbon concentrations, P-restricted conditions (≤0.3 μg P·L−1) limited bacterial growth (lower values of ATP, TCC). A faster pressure drop increase was observed for P-restricted conditions compared to P-dosed conditions when 250 μg C·L−1 was dosed. This faster pressure drop increase can be explained by a higher area covered by biofilm in the flow channel and a higher amount of produced EPS. Conversely, a slower pressure drop increase was observed for P-restricted conditions compared to P-dosed conditions when 30 μg C·L−1 was dosed. Results of this study demonstrate that P-limitation delayed biofilm formation effectively when combined with low assimilable organic carbon concentration and thereby, lengthening the overall membrane system performance.

Evaluation of the efficiency of three different mineral adsorbents in the removal of pollutants in samples from a tropical spring in Northeastern Brazil.

Human water sources are increasingly threatened around the world due to various sources of pollution such as agriculture and industry. The objective of this study was to evaluate three new adsorbents as pollutant remedies for subsequent application in the Joanes River located in the State of Bahia in Brazil. The specific pollutants were nitrogen, phosphorus (P), aluminum (Al), iron (Fe), cyanobacteria, and saxitoxins. Initially, studies (pH 7 and 22°C) were performed with samples contaminated in the laboratory with phosphorus (P), nitrate ( ), and ammonia (NH3 ), to select the most efficient adsorbent and to determine the equilibrium time. Pumice bituminous coal was found to have the best efficiencies (≥70%) at 360min (equilibration time). The experimental data did not fit the Langmuir and Freundlich model. The bituminous coal with pumice stone was then applied to water samples from a designated capture point of the Joanes springs, a river system that is responsible for supplying the city of Salvador and the metropolitan region, located on the northern coast of Bahia. The removal efficiency analyses were performed on a DR6000 UV/VIS SPECTROPHOTOMETER, using the methodology defined in the Standard Methods 2017, after which this adsorbent was subjected to scanning electron microscopy. As a result, removal efficiencies (≥98%) were obtained for all contaminants (nitrogen, phosphorus (P), aluminum (Al), iron (Fe), cyanobacteria, and saxitoxins) as well as a highly heterogeneous layer pointed by SEM images, further demonstrating the adsorbent potential as a efficient alternative in environmental control after additional studies. PRACTITIONER POINTS: Pumice bituminous coal has proven to be an excellent adsorbent for a wide range of pollutants such as phosphorus, nitrogen, ammonia, toxins, cyanobacteria, and metals. The adsorbent promoted a high reduction in phosphorus concentrations (3.40mg/L to 0.01mg/L), about 98% and 81% for cyanobacteria (12,850Cel/ml to 2,560Cel/ml). The adsorbent promoted a high reduction in concentrations of 98% saxitoxins (4.32µg/L to 0.2µg/L).

Multi-scale characterisation of stream nutrient and carbon dynamics in sandy near coastal catchments of south-western Australia

Managers tasked with repairing degraded stream ecosystems require restoration strategies that are tailored to local and regional characteristics. Emerging evidence suggests that local reach-scale approaches may be as effective, if not more so, than catchment-scale actions in highly permeable coastal landscapes, particularly if there is hydraulic connectivity to shallow groundwater and where recharge is strongly seasonal. This study assessed the relative influence of catchment-scale land use and reach-scale vegetation structure on the distribution of carbon and nutrient concentrations of streams within urban and agricultural catchments of the Perth region of south-western Australia. We used linear mixed-effects models to evaluate the extent to which phosphorus, nitrogen and carbon concentrations in different stream zones (streamwater, and fluvial and parafluvial sediments) were explained by catchment and reach-scale attributes and moderated by high versus low-flow periods, i.e., in wet versus dry months. We found that reach-scale vegetation (woody plant cover, annual plant cover) was a better predictor of nutrient concentrations than catchment-scale land use, particularly total imperviousness, a common measure of urbanisation. Flow was also important, with carbon and nutrient concentrations better described by reach- or catchment-scale attributes during the low flow period. The extent to which individual catchment and reach attributes influenced the distribution of nutrients in different stream zones was complex. However, our results suggest that planting woody vegetation can reduce nitrogen concentrations in surface water and fluvial sediments. Reducing the abundance of weedy annual species and restoring woody perennial species may further reduce phosphorus concentrations in surface water. We conclude that local riparian restoration can be a cost-effective strategy for managing excess nutrients and carbon in flat and permeable urban landscapes, particularly during low flow periods.

Lime application to reduce phosphorus release in different textured intact and small repacked soil columns

Phosphorus (P) losses from agricultural fields through leaching are the main contributors to eutrophication of lakes and rivers in North America. Adoption of P-retaining strategies is essential to improve the environmental quality of water bodies. The main objective of this study is to evaluate lime as a soil amendment in reducing phosphorus concentration in the leachate from three common soil textures with neutral to alkaline pH. Phosphorus leaching from undisturbed soil columns (10 cm in diameter and 20 cm deep) as well as small repacked columns was investigated and compared in this study. Lime (high calcium hydrated lime) at the rate of 1% by air-dried soil mass was applied to the topsoil of the columns. Both sets of experiments followed a full factorial design with two factors of soil texture at three levels (sandy loam, loam, and clay loam) and treatment at two levels (control and limed) with three replicates. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy was performed on the control and limed soil samples to confirm the formation of calcium phosphate compounds. For both intact and repacked columns, dissolved reactive phosphorus (DRP) concentrations in the leachates from limed sandy loam and limed loam soil columns was significantly reduced, while DRP in the limed clay loam column leachates was not changed. Elemental mapping demonstrated that in limed sandy loam and loam soils, the calcium loadings on the soil surface were always linked with phosphorus. The formation of calcium phosphate compounds and the increased phosphate adsorption on the soil surface through Ca bridging could be the two main phosphorus-lime retention mechanisms. Total dissolved phosphorus (TDP) in the leachates of limed loam and limed clay loam indoor intact and repacked columns was reduced, while there was no change in that of the sandy loam soil. In finer textured soils, lime can increase TDP retention through the immobilization of organic phosphates. The impact of lime application on DRP and TDP varied with the soil texture. The lime-induced reduction in the DRP and TDP was variable between the intact and repacked columns demonstrating the importance of soil structure on phosphorus and lime interactions in the soil. Overall, lime application at the studied rate can be considered a promising soil amendment in mitigating phosphorus loss from non-calcareous neutral to alkaline soils.

Is on-site wastewater a significant source of phosphorus to coastal plain streams?

On-site wastewater systems are commonly used to treat wastewater in rural areas, and many studies have shown these systems to be efficient at reducing phosphorus concentrations. However, as rural areas urbanize and the density of on-site systems increases, effluent discharges to the subsurface may contribute to water quality degradation. Many residences (~ 50%) use on-site systems in North Carolina where excess nutrient loadings have caused water use impairment. The goal of this study was to determine whether on-site system inputs had a measurable influence on stream phosphorus concentrations and loads. Seven watersheds including 3 served by on-site systems and 4 control watersheds served by a municipal sewer system in coastal North Carolina were sampled each month for 13 months during baseflow conditions and during two storm events for total phosphorus and total dissolved phosphorus analyses and physical and chemical characterization. Watersheds served by on-site systems had significantly (p < 0.05) larger concentrations of total phosphorus and total dissolved phosphorus relative to the control watersheds (municipal sewer) that did not receive wastewater discharges. Mass loads of total phosphorus and total dissolved phosphorus were also significantly (p < 0.05) greater from watersheds served by on-site systems relative to municipal sewer. These data suggest that on-site systems influenced the water quality of streams with regard to in-stream phosphorus concentrations and led to higher phosphorus loading to downstream aquatic ecosystems relative to control watersheds. Watershed nutrient management plans should address phosphorus contributions from both on-site systems and municipal sewer systems in coastal plain regions.

Fe(II)-dosed ceramic membrane bioreactor for wastewater treatment: Nutrient removal, microbial community and membrane fouling analysis

Ferrous dosing is used to reduce phosphorus concentration and alleviate polymeric membrane fouling in membrane bioreactor (MBR). However, limited studies have been conducted to investigate the impacts of ferrous dosing on ceramic membrane fouling, nutrient removal efficiency and microbial community. Accordingly, the aim of this study was to investigate the effect of intermittent ferrous dosing with Fe/P molar ratios of 2 and 1 (with a dosing frequency of every two days) on the overall nutrient removal, functional microbial changes and membrane fouling in ceramic membrane bioreactors (CMBR) in treatment of wastewater. TP concentration of 10 mg/L in influent decreased to 1.94 ± 0.62 mg/L (control), 0.38 ± 0.22 mg/L (Fe/P = 1) and 0.31 ± 0.18 mg/L (Fe/P = 2) in the effluent, respectively. Meanwhile, the effluent total nitrogen (TN) concentrations with Fe/P = 1 treatment (6.80 ± 2.02 mg/L) and Fe/P = 2 treatment (5.12 ± 2.28 mg/L) were lower than that of the control (7.72 ± 2.36 mg/L). Compared to Fe/P = 1, the TN removal performance was better for Fe/P = 2 mainly due to the increased abundance of denitrifying bacteria (Zoogloea and Acinetobacter). In addition, excess iron dose might have toxic effects on bacterial physiology, however the Fe concentrations that cause cell damage vary for different bacteria. The relative abundance of Zoogloea (aerobic denitrifying bacteria) continuously increased with ferrous addition (Fe/P = 2), while other bacteria including Dechloromonas, Hyphomicrobium and Thauera (anoxic denitrifying bacteria), Nitrospira (nitrifying bacteria) and Candidatus Accumulibacter (phosphorus accumulating organism) decreased sharply. Furthermore, membrane fouling was effectively moderated by ferrous dosing and Fe/P = 1 treatment showed improved membrane fouling mitigation than Fe/P = 2. Overall, intermittent ferrous addition in CMBR with Fe/P molar ratio of 1 was beneficial to the removal of nutrients (TP, TN and organics), enhanced succession of microbial community and membrane fouling mitigation.

Weekly water quality monitoring data for the River Thames (UK) and its major tributaries (2009–2013): the Thames Initiative research platform

Abstract. The River Thames and 15 of its major tributaries have been monitored at weekly intervals since March 2009. Monitored determinands include major nutrient fractions, anions, cations, metals, pH, alkalinity, and chlorophyll a and are linked to mean daily river flows at each site. This catchment-wide biogeochemical monitoring platform captures changes in the water quality of the Thames basin during a period of rapid change, related to increasing pressures (due to a rapidly growing human population, increasing water demand and climate change) and improvements in sewage treatment processes and agricultural practices. The platform provides the research community with a valuable data and modelling resource for furthering our understanding of pollution sources and dynamics, as well as interactions between water quality and aquatic ecology. Combining Thames Initiative data with previous (non-continuous) monitoring data sets from many common study sites, dating back to 1997, has shown that there have been major reductions in phosphorus concentrations at most sites, occurring at low river flow, and these are principally due to reduced loadings from sewage treatment works (STWs). This ongoing monitoring programme will provide the vital underpinning environmental data required to best manage this vital drinking water resource, which is key for the sustainability of the city of London and the wider UK economy. The Thames Initiative data set is freely available from the Centre for Ecology and Hydrology's (CEH) Environmental Information Data Centre at https://doi.org/10.5285/e4c300b1-8bc3-4df2-b23a-e72e67eef2fd.

Temporal (1970–2016) changes in human pressures and wetland response in the St. Lawrence River (Québec, Canada)

Temporal changes (1970–2016) in St. Lawrence River wetlands were assessed between Cornwall and Québec (≈400 km) to assess wetland response to cumulative anthropogenic pressures in the watershed. Emergent wetlands area and biomass of submerged aquatic vegetation (SAV) were contrasted among five regions subjected to sharply different water level/discharge regime (stabilized, semi-natural, tidal), nutrient concentrations and shoreline use (rural to urbanized). Between 1970 and 2016, over the growing season (April–Sept.), St. Lawrence River mean water level at Sorel dropped by ≈1 m and mean water temperature increased by ≈3 °C. Reductions in phosphorus concentrations (by ≈2-fold) were observed over time both in water and in SAV tissues, in phase with improvements of urban wastewater treatment and P-reduction in upstream Lake Ontario. Nitrate concentrations in water increased and SAV biomass decreased between the 1970s and 2008 in the downstream regions of Lake Saint-Pierre and fluvial corridor subjected to the cumulative impacts from urban centers and intensively farmed watersheds. Over the 1970–2010 period, dropping water levels yielded slightly increasing wetland areas, owing to the downslope colonization of emergent and submerged plants. In urbanized regions, emergent wetlands shifted towards drier assemblages dominated by invasive reed species. Encroachment of wetlands by agriculture accounted for most wetland losses in rural Lake Saint-Pierre, which holds the single largest area (197 km2) of continuous wetland habitat of the entire watershed. Our results highlight the strong response of riverine wetlands to a wide range of human pressures, including dropping water levels, changing nutrient concentrations, rising population and intensifying agriculture.

Reducing drainage water phosphorus concentration with rice cultivation under different water management regimes

Phosphorus is a critical water quality indicator of farm drainage systems. In South Florida, rice (Oryza sativa L.) cultivation has the potential to reduce phosphorus concentration in drainage water through crop uptake under varying flooding systems. A two-year study was conducted to assess drainage water quality under four different flooding systems conventionally used for rice production – 15 cm continuous flood; 5 cm continuous flood; 15 cm with midseason drawdown; and 5 cm with midseason drawdown. In the first growing season, 15 cm continuous flood treatment had the highest reduction of total phosphorus and particulate phosphorus concentrations in drainage water. However, in the second growing season, we did not observe significant differences among water treatments, which was likely due to the release of phosphorus from other sources like soil and rice straw to the water column which masked treatment effects. On average, in both years, all flood treatments reduced total phosphorus concentrations by 42 ± 8% between inflow and outflow water. No phosphorus fertilizer was added and with each harvest, rice grain potentially removed 15.7 ± 3 kg phosphorus ha−1. The results indicate that rice cultivation in fertile soils can successfully reduce phosphorus concentrations in drainage water under well managed water-flow conditions.

Closing the cycle: Phosphorus removal and recovery from diluted effluents using acid resistive membranes

New regulations in many developed countries call for significant reduction in phosphorus concentration for effluents released to the environment. At the same time, recovery of phosphorus – a non-renewable resource used mainly as fertilizer – from anthropogenic waste is extensively studied and bolstered as a crucial component in maintaining future food security. Thus far, studies on phosphorus recovery mainly focused on concentrated streams; although diluted effluents such as treated wastewater often contain a significant portion of the phosphorus mass. Here we propose a new approach for the simultaneous removal and recovery of phosphorus from diluted effluents using a membrane characterized by high phosphate rejection and acid resistance. High P rejection allows for the concentration of phosphorus in the retentate until recoverable calcium-phosphate precipitants are formed, while acid resistance enables a simple and effective chemical cleaning of the membrane. Factors affecting the removal and recovery of phosphorus during filtration are studied here experimentally and through thermochemical modeling. CaCO3 precipitation in the retentate resulted in severe scaling, whereas calcium-phosphate precipitated mostly in the bulk, resulting in colloidal fouling which was manageable by maintaining sub-critical permeate flux. Selective Ca-P precipitation is feasible via pH adjustments, requiring very little acid addition as shown through thermochemical modeling. Calcium-phosphate deposits were easily removed from the feed channel using acid-cleaning, and the permeate flux was completely restored. Furthermore, phosphorus removal and recovery by nanofiltration was shown to require less operating expenses compared to a more conventional approach comprising P removal by ferric chloride addition and its subsequent recovery from incinerated sludge. Our results therefore demonstrate the potential of this new approach as a step forward towards closing the anthropogenic phosphorus cycle.