Total Phosphate Concentrations Research Articles

Source-specific sewage pollution detection in urban river waters using pharmaceuticals and personal care products as molecular indicators.

Source-specific elucidation of domestic sewage pollution caused by various effluent sources in an urban river water, as conducted for this study, demands knowledge of the relation between concentrations of pharmaceuticals and personal care products (PPCPs) as molecular indicators (caffeine, carbamazepine, triclosan) and water quality concentrations of total nitrogen (T-N) and total phosphorous (T-P). River water and wastewater samples from the Asahikawa River Basin in northern Japan were analyzed using derivatization-gas chromatography/mass spectrometry. Caffeine, used as an indicator of domestic sewage in the Asahikawa River Basin, was more ubiquitous than either carbamazepine or triclosan (92-100%). Its concentration was higher than any target compound used to assess the basin: <4.4-370ng/L for caffeine, <0.6-3.9ng/L for carbamazepine, and <1.1-13ng/L for triclosan. Higher caffeine concentrations detected in wastewater effluents and the strongly positive mutual linear correlation between caffeine and T-N or T-P (R 2>0.759) reflect the contribution of septic tank system effluents to the lower Asahikawa River Basin. Results of relative molecular indicators in combination with different molecular indicators (caffeine/carbamazepine and triclosan/carbamazepine) and cluster analysis better reflect the contribution of sewage than results obtained using concentrations of respective molecular indicators and cluster analysis. Relative molecular indicators used with water quality parameters (e.g., caffeine/T-N ratio) in this study provide results more clearly, relatively, and quantitatively than results obtained using molecular indicators alone. Moreover, the caffeine/T-N ratio reflects variations of caffeine flux from effluent sources. These results suggest strongly relative molecular indicators are also useful indicators, reflecting differences in spatial contributions of domestic sources for PPCPs in urban areas.

Performance of constructed wetland applied for domestic wastewater treatment: Case study at Boimorto (Galicia, Spain)

The study aims at evaluating the performance of a horizontal subsurface flow constructed wetland used for secondary treatment of domestic wastewater since May 2011 at Galicia (Spain). A septic tank was used as primary treatment. The wetland consists of two cells in parallel: cell-A with 350m2 and cell-B with 280m2, constructed with a depth of 0.6m, filled with gravel of 30mm of average size and planted with common reeds. The performance of wastewater treatment was controlled from June 2011 to September 2015. The rural agglomeration is served by a gravity sewer system with high rates of infiltration/inflow during wet weather. Thus, concentration and flow rate of wastewater have high seasonal variability. Average primary effluent BOD5, COD, suspended solids (TSS), total nitrogen (TN) and total phosphorous (TP) concentrations (in mg/L) were: 105, 197, 43, 29 and 3.4, respectively. Meanwhile, average secondary effluent BOD5, COD, SS, TN and TP values (in mg/L) were: 19, 44, 12, 14.3 and 1.9, respectively. A 2.2 log unit reduction for faecal coliforms was observed in the global system. The wetland required to be harvested at the end of each October. The sludge produced by the septic tank has not yet required to be removed. The wetland system presented no problems for vectors or nuisance odours.

Performance Evaluation of a Floating Treatment Wetland in an Urban Catchment

Floating Treatment Wetland (FTW) systems are purpose-built devices designed to replicate the water treatment processes that occur in and around naturally occurring floating vegetated islands. FTWs can be used to improve the water quality of water storage ponds by contributing to water treatment processes through adhesion, filtration, nutrient uptake (direct use by plants), and sequestration. This paper presents the results of a twelve-month investigation into the pollution removal performance of a FTW receiving stormwater runoff from a 7.46 ha urban residential catchment. As anticipated, there was a high degree of variation in FTW treatment performance between individual rainfall events. Overall pollution removal performance was calculated to be 80% for Total Suspended Solids (TSS), 53% for Total Phosphorous (TP), and 17% for Total Nitrogen (TN) for a FTW footprint of 0.14% of the contributing catchment. TSS and TP concentrations were found to be significantly reduced after FTW treatment. The minimum FTW footprint to catchment size ratio required to achieve regulated nutrient removal rates was calculated to be 0.37%. Sum of loads calculations based on flow resulted in pollution load reductions of TSS 76%, TP 55%, and TN 17%. Pollution treatment performance (particularly for TN) was found to be affected by low influent concentrations, and highly-variable inflow concentrations. The study demonstrated that FTWs are an effective treatment solution for the removal of pollution from urban stormwater runoff.

Spatial and seasonal dynamics of fish assemblage along river Soan, Pakistan and its relationship with environmental conditions

This study aims to discuss the seasonal and spatial dynamics of fish assemblage of River Soan in relation with environmental changes. Survey was conducted during pre monsoon and post monsoon seasons in 2008. Physico chemical and biological samplings were carried out at 26 sites which were selected along the whole stretch of the river. High concentration of total phosphorous and conductivity, low pH and dissolved oxygen were measured at urban part of midstream zone whereas high concentration of total nitrogen was measured at downstream zone. A total of 22 species were collected during the survey among which Barilius pakistanicus, Puntius ticto, Crossocheilus diplochilus and Labeo dero were distributed throughout the river stretch. Maximum fish diversity was recorded at suburban part of midstream while its urban part was appeared to be the most species poor part of the Soan River. Herbivore individuals constituted the dominant trophic group of fish assemblage. Significant seasonal and spatial changes in fish assemblage were determined at river downstream. Upstream- downstream differences in fish assemblage were more pronounced during pre monsoon and seem to be related to thermal gradient and hydrological changes. Seasonal variations in fish assemblage were significant only at downstream zone and were influenced by velocity, floodplains and migration patterns in fish assemblage. Understanding of spatial and seasonal trends in fish assemblage in relation with their environment is of great importance for the management and conservation of fish assemblage. Findings of this study will be helpful in future attempts to restore and conserve the aquatic assemblages of Himalayan streams.

Selective withdrawal optimization in river-reservoir systems; trade-offs between maximum allowable receiving waste load and water quality criteria enhancement.

In this paper, a new systematic approach is designed to maximize the demand coverage and receiving waste load by river-reservoir systems while enhancing water quality criteria. The approach intends to control the reservoir eutrophication while developing a trade-off between the maximum receiving load and shortage on demand coverage. To simulate the system, a hybrid process-based and data-driven model is tailored. Initially, the two-dimensional hydrodynamics and water quality simulation model (CE-QUAL-W2) is linked with an effective single and/or multiple optimization algorithms (PSO) to evaluate the proposed scenarios. To increase the computational efficiencies, the simulation model is substituted with a surrogate model (ANN) in an adaptive-dynamically refined routine. The proposed method is illustrated by a case study in Iran, namely, Karkheh River Reservoir, for 180-monthly periods. The results showed the applicability of the methodology especially to solve high-dimensional multi-period complex water resource optimization problems. Also, the results demonstrated that eutrophication could be reduced under the optimal inflow phosphate control and reservoir operation, regulating the total phosphorous concentration in the reservoir.

Ten-year change of total phosphorous pollution in the Min River, an upstream tributary of the Three Gorges Reservoir

Understanding the spatial and temporal variation of nutrient concentrations, loads and their distribution from upstream tributaries is important for management of large lakes and reservoirs. The Min River is an important tributary of the upper reaches of the Three Gorges Reservoir (TGR) that contributes about 20 % of the inflow water from the Yangtze River to the TGR. It is also one of the main phosphorous sources of the TGR. In this study, total phosphorous (TP) concentrations and hydrological data from 2004 through 2014 for 13 sites in Min River and its tributaries were analyzed. The result suggested that the concentration of TP was comparatively lower in the upstream of the Min River and Dadu River, but tended to increase in recent years. Additionally, the TP pollution status in the Min River basin has gradually evolved from local pollution to whole-basin pollution. The concentration of TP in the Min River main stream increased, decreased and then increased again along the waterway. Pollution from nonpoint sources was the main contribution in the upstream portion and Outer River basin of Min River. Pollution from point sources was more serious than that from nonpoint sources in Chengdu, Meishan and Leshan segment. Specifically, TP pollution in Min River of Chengdu segment (Huanglongxi, Inner River) was primarily affected by urbanization, while Leshan segment (Yuebo) was mainly affected by glyphosate production. Controlling pollution from nonpoint sources and improving the sewage collection rate to reduce TP loads will be the primary task in the upstream portion and Outer River basin. Point source pollution controlling will still be the primary task associated with water quality management in the Inner River (Chengdu segment) and the downstream (Leshan segment) basin of Min River for the foreseeable future. Pollution from both point sources and nonpoint sources should be cared in the other area of Min River basin.

Descriptive analysis of the masticatory and salivary functions and gustatory sensitivity in healthy children

Objective: The objective of this study is to better understand salivary and masticatory characteristics, this study evaluated the relationship among salivary parameters, bite force (BF), masticatory performance (MP) and gustatory sensitivity in healthy children. The secondary outcome was to evaluate possible gender differences.Materials and methods: One hundred and sixteen eutrophic subjects aged 7–11 years old were evaluated, caries-free and with no definite need of orthodontic treatment. Salivary flow rate and pH, total protein (TP), alpha-amylase (AMY), calcium (CA) and phosphate (PHO) concentrations were determined in stimulated (SS) and unstimulated saliva (US). BF and MP were evaluated using digital gnathodynamometer and fractional sieving method, respectively. Gustatory sensitivity was determined by detecting the four primary tastes (sweet, salty, sour and bitter) in three different concentrations. Data were evaluated using descriptive statistics, Mann–Whitney/t-test, Spearman correlation and multiple regression analysis, considering α = 0.05.Results: Significant positive correlation between taste and age was observed. CA and PHO concentrations correlated negatively with salivary flow and pH; sweet taste scores correlated with AMY concentrations and bitter taste sensitivity correlated with US flow rate (p < 0.05). No significant difference between genders in salivary, masticatory characteristics and gustatory sensitivity was observed. The regression analysis showed a weak relationship between the distribution of chewed particles among the different sieves and BF.Conclusions: The concentration of some analytes was influenced by salivary flow and pH. Age, saliva flow and AMY concentrations influenced gustatory sensitivity. In addition, salivary, masticatory and taste characteristics did not differ between genders, and only a weak relation between MP and BF was observed.

English

A study was conducted from July 2013 to June 2014 to assess the outcome of dredging activity on the water characteristics and zooplankton community structure in Dal Lake. An assessment was done with respect to alterations in physico-chemical parameters and zooplankton community changes in pre-dredged and post-dredging periods. The results showed a considerable reduction in Secchi transparency while water depth, conductivity, total dissolved solids, nitrate and total phosphorous concentrations increased noticeably in post dredging scenario. Variations in the values of dissolved oxygen, pH and temperature as a result of dredging were not statistically significant. The environmental changes as a result of dredging activity affected the structure and distribution of zooplankton community; the abundance of rotifers decreased, while the crustaceans increased. The prominent taxa were Brachionus sp., Keratella cochlearis, Bosmina longirostris, Chydorus sphaericus and Diaptomus sp. Key words: Dredging, water quality, zooplankton, rotifer, crustacean.

Assessing the Impacts of Climate and Land Use Changes on the Water Quality of a Transboundary Balkan River

The Mediterranean area is highly vulnerable to climate changes that combined with potential land use changes could influence its aquatic systems significantly. The Evros River is one of the most important surface water bodies in the Balkans with an ecologically significant delta that is protected by international legislation. The aim of this study is to analyze the impacts of climate and land use changes on Evros River water quality, for different climatic and socioeconomic scenarios. For this purpose, a hydrodynamic and advection-dispersion model was set up and calibrated, three IPCC climatic scenarios were applied, and the pollution loads of the catchment area were estimated. These scenarios involved river discharge decrease due to regional climate changes and socioeconomic and technological development that would lead to population growth and to the decrease of agricultural activities. The results indicated that in the case of discharge reduction only, the total nitrate and phosphate concentrations will be increased, while in case of combined land use and discharge changes, the concentration of nutrients will be decreased. Thus, a transboundary long-term management plan of the entire River is needed that would eliminate the pollution pressures and restore its good ecological status.

Estimating spatio-temporal dynamics of stream total phosphate concentration by soft computing techniques

This study attempts to model the spatio-temporal dynamics of total phosphate (TP) concentrations along a river for effective hydro-environmental management. We propose a systematical modeling scheme (SMS), which is an ingenious modeling process equipped with a dynamic neural network and three refined statistical methods, for reliably predicting the TP concentrations along a river simultaneously. Two different types of artificial neural network (BPNN—static neural network; NARX network—dynamic neural network) are constructed in modeling the dynamic system. The Dahan River in Taiwan is used as a study case, where ten-year seasonal water quality data collected at seven monitoring stations along the river are used for model training and validation. Results demonstrate that the NARX network can suitably capture the important dynamic features and remarkably outperforms the BPNN model, and the SMS can effectively identify key input factors, suitably overcome data scarcity, significantly increase model reliability, satisfactorily estimate site-specific TP concentration at seven monitoring stations simultaneously, and adequately reconstruct seasonal TP data into a monthly scale. The proposed SMS can reliably model the dynamic spatio-temporal water pollution variation in a river system for missing, hazardous or costly data of interest.

Phosphorus body content in an herbivorous fish in environments with different trophic state

&lt;p&gt;Animals are believed to be homeostatic by maintaining relatively constant body nutrient content independently of changes in diet. Phosphorus (P) is one of the most important elements for fishes as Loricariids, which are covered with armor-like bony plates. These species are expected to maintain nutrient homeostasis, however, in environments with low P availability they can be P-limited. The hypothesis of this study is that P concentration in body composition of an herbivorous fish, &lt;em&gt;Hypostomus jaguribensis,&lt;/em&gt; does not change in environments with different availability of this nutrient. We conducted this study in two locations of the Curu river basin in Brazil, which differed in their nutrient concentrations: one was ultraoligotrophic and the other mesotrophic, as determined by total phosphorous concentrations and chlorophyll &lt;em&gt;a&lt;/em&gt; in the water. We found significant differences in the body P content of the fish from the two sites: &lt;em&gt;Hypostomus jaguribensis&lt;/em&gt; from the ultraoligotrophic site showed higher body P content, higher body weight and condition factor. This suggests that the ultraoligotrophic site is a more favorable environment for this species. The body P content was higher in intermediate sizes (between 12 and 14 cm in the ultraoligotrophic site and between 11 and 13 cm in the mesotrophic site), which can be related to biological characteristics such as the need to accumulate nutrients at the beginning of the reproductive period. Our study did not find support for strict homeostasis in this high-P demand fish species.&lt;/p&gt;

Assessment of the Spatial and Temporal Variations of Water Quality for Agricultural Lands with Crop Rotation in China by Using a HYPE Model.

Many water quality models have been successfully used worldwide to predict nutrient losses from anthropogenically impacted catchments, but hydrological and nutrient simulations with limited data are difficult considering the transfer of model parameters and complication of model calibration and validation. This study aims: (i) to assess the performance capabilities of a new and relatively more advantageous model, namely, Hydrological Predictions for the Environment (HYPE), that simulates stream flow and nutrient load in agricultural areas by using a multi-site and multi-objective parameter calibration method and (ii) to investigate the temporal and spatial variations of total nitrogen (TN) and total phosphorous (TP) concentrations and loads with crop rotation by using the model for the first time. A parameter estimation tool (PEST) was used to calibrate parameters. Results show that the parameters related to the effective soil porosity were highly sensitive to hydrological modeling. N balance was largely controlled by soil denitrification processes. P balance was influenced by the sedimentation rate and production/decay of P in rivers and lakes. The model reproduced the temporal and spatial variations of discharge and TN/TP relatively well in both calibration (2006–2008) and validation (2009–2010) periods. Among the obtained data, the lowest Nash-Suttclife efficiency of discharge, daily TN load, and daily TP load were 0.74, 0.51, and 0.54, respectively. The seasonal variations of daily TN concentrations in the entire simulation period were insufficient, indicated that crop rotation changed the timing and amount of N output. Monthly TN and TP simulation yields revealed that nutrient outputs were abundant in summer in terms of the corresponding discharge. The area-weighted TN and TP load annual yields in five years showed that nutrient loads were extremely high along Hong and Ru rivers, especially in agricultural lands.

Characterization of morphology and component of struvite pellets crystallized from sludge dewatering liquor: Effects of total suspended solid and phosphate concentrations

A lab-scale struvite pellet crystallization system was used to study phosphorus (P) removal and recovery from sludge dewatering liquor (SDL). Influences of total suspended solids (TSS) and phosphate concentrations on P removal as well as the size, morphology, purity, and components of struvite pellets were investigated. The increase in TSS concentration resulted in not only the decreases in phosphate removal efficiency and struvite purity but also the irregular pellet morphology and broken struvite crystals. Increasing inlet PO4-P concentration enhanced PO4-P removal, average struvite pellet diameter, purity and crystal volume growth rate. Amorphous calcium phosphate (ACP), calcite, brucite and magnesium phosphate were formed as co-precipitates with struvite. However, species and quantity of co-precipitates could be variable. More calcium precipitates were easily formed at lower PO4-P concentration (48mg/L), while brucite was the main co-precipitate at higher PO4-P concentration (151mg/L). Organic compounds were involved in struvite pellets along with suspended solids during the formation of struvite. Higher TSS concentration resulted in both more species and higher contents of organic compounds in struvite pellets. Therefore, it is essential to remove suspended solids in advance so as to obtain high P-removal and harvest high-quality struvite pellets.

How Protective Mechanisms Interact to Prevent Overnight Calcium Phosphate Precipitation - An Observational Study to Determine Factors Against Calcium Phosphate Lithogenesis in a Healthy Cohort

Background/Aims: As restful, non-interrupted sleep is essential for normal mental and physical functioning, the urine flow rate (U_FR) overnight remains low. Due to this reduced U_FR, the kidneys produce a lower urine volume, which may lead to supersaturation of lithogens in the renal collecting system. The protective mechanisms that prevent the rise in the concentration of the lithogenic substances in urine, such as calcium phosphate, are explored. Methods: Urine samples were collected from 26 subjects every 2-3 h during daylight with one nocturnal collection; the U_FR was calculated in the median time for each collection period. Urinary constituents for calcium phosphate precipitation including electrolytes, calcium, phosphate, citrate, and pH were measured. Comparisons within individuals were done by paired t test. Results: The calcium excretion rate fell significantly overnight (from 2.4 ± 0.2 µmol/min during the daytime to 1.5 ± 0.3 µmol/min, p < 0.05), in parallel with sodium excretion (54 ± 16 µmol/min from its daytime 127 ± 12 µmol/min, p < 0.05), preventing nocturnal calcium concentration from increasing (3.0 ± 0.3 mmol/l daytime to 2.5 ± 0.5 mmol/l overnight), while citrate concentration did not change significantly. The total urine phosphate concentration rose significantly overnight (daytime 18.7 ± 1.4 µmol/min vs. nocturnal 20.9 ± 1.7 µmol/min), but the concentration of divalent phosphate did not increase in the overnight period. Conclusions: Although the U_FR was lower overnight, there was no evidence that the risk of calcium phosphate precipitate formation in healthy subjects was increased.

Modeling total particulate organic carbon (POC) flows in the Baltic Sea catchment

The largest input source of carbon to the Baltic Sea catchment is river discharge. A tool for modeling riverine particulate organic carbon (POC) loads on a catchment scale is currently lacking. The present study describes a novel dynamic model for simulating flows of POC in all major rivers draining the Baltic Sea catchment. The processes governing POC input and transport in rivers described in the model are soil erosion, in-stream primary production and litter input. The Baltic Sea drainage basin is divided into 82 sub-basins, each comprising several land classes (e.g. forest, cultivated land, urban areas) and parameterized using GIS data on soil characteristics and topography. Driving forces are temperature, precipitation, and total phosphorous concentrations. The model evaluation shows that the model can predict annual average POC concentrations within a factor of about 2, but generally fails to capture the timing of monthly peak loads. The total annual POC load to the Baltic Sea is estimated to be 0.34 Tg POC, which constitutes circa 7–10 % of the annual total organic carbon (TOC) load. The current lack of field measurements of POC in rivers hampers more accurate predictions of seasonality in POC loads to the Baltic Sea. This study, however, identifies important knowledge gaps and provides a starting point for further explorations of large scale POC mass flows.

Sequential extraction of different forms of phosphorus in the surface sediments of Chilika Lake

Sequential chemical extractions were used to study the spatial and temporal distribution of different forms of phosphorus (P) in the surface sediments of Chilika, the largest brackish water lake in Indian subcontinent. Sediments were analyzed for different forms of phosphorus along with some sedimentary parameters such as sand, mud, and organic carbon. The lake sediments are found to be mostly sandy near outer channel, whereas other parts of the lake are muddy sand type. Among the inorganic phosphorous fractions, calcium-bound P (Ca-P) emerged as the most dominant fraction contributing 55 and 37 % of the total phosphorous (TP) respectively in pre- and post-monsoon seasons, respectively. Contribution of loosely bound phosphorus (Lo-P) to the TP in lake system was the lowest (<1 %) in both the seasons. TP concentration of the lake sediment ranged from 291.9 to 1653.4 mg/kg with an average of 1047.71 mg/kg in pre-monsoon and 243.97–2150.55 mg/kg with an average of 1100.81 mg/kg in post-monsoon seasons. The bioavailable fraction contributes 1.4–26.7 % with average of 23.8 % in pre-monsoon whereas it contributes 32.1–34.32 % with an average of 35.72 % of TP in post-monsoon. The order of abundance of the major forms of P in the surface sediments of Chilika Lake was as follows: Lo-P < Al-P < Fe-P < O-P < Ca-P for both the seasons. Correlation matrix and factor analysis were used for result interpretation.

Changes in particle size, calcium and phosphate solubilization, and microstructure of rehydrated milk protein concentrates, prepared from partially acidified milk

The present work studied the rehydration properties of milk protein concentrates (MPCs), prepared using ultrafiltration (UF) and diafiltration (DF). Milk was acidified to pH 6 with glucono-δ-lactone (GDL) prior to UF to alter the mineral composition of the final concentrates. The particle size distribution and the microstructure of the casein micelles in reconstituted MPCs as well as the partitioning of calcium, phosphate, and proteins between the colloidal and soluble phases were investigated. Reconstituted samples analyzed by electron microscopy showed that, even in partially dissolved particles, the particle surface was porous and similar to its inner portion and had no distinct skin layer. Partial acidification of milk did not have any significant effects on the microstructure; however, it significantly increased the average diameter of the casein micelles for both UF and DF samples and decreased the concentration of total calcium and phosphate. Sodium dodecyl sulfate (SDS)-PAGE analysis of the centrifugal supernatants of reconstituted MPC demonstrated that the amount of soluble caseins present in milk concentrates dramatically increased with acidification, and it further increased after restoring the mineral composition of the serum phase through dialysis against milk. This work contributes to a better understanding of how processing conditions, particularly partial acidification of milk prior to concentration, can alter the composition and physical properties of the caseins and the soluble phase of MPC after rehydration. Such alterations can significantly impact the technological properties of the reconstituted MPC.

Limnological assessment of the meteo-hydrological and physicochemical factors for summer cyanobacterial blooms in a regulated river system

This study aimed to explain how the changes in certain hydrological, meteorological and physicochemical factors influence the cell density of the cyanobacteria Microcystis aeruginosa in the Nakdong River. Occurrence patterns of M. aeruginosa were analyzed between 1993 and 2010 (N =96) using a self-organizing map. The cell density of M. aeruginosa was sensitive to certain meteorological, hydrological and physicochemical factors. In addition, our clustering analysis results identified specific limnological features under different environmental conditions. Cluster 1 suggested that high rainfall and increased river flow, dam discharge, total phosphorous and phosphate concentrations were associated with low M. aeruginosa cell density (June–July; monsoon season). However, cluster 2 suggested low irradiance since water temperature decreases with irradiation time, and thus low M. aeruginosa cell density (April–June and after November). Finally, cluster 3 was indicative of high water temperature and irradiance, increased irradiation time, low phosphate and nitrate concentrations, and high M. aeruginosa cell density (August, after the monsoon season). Taken together, these results suggest that rainfall, river flow, water temperature and nutrient concentration (i.e. , phosphates and nitrates) were the primary factors that affected cyanobacterial bloom occurrence in the Nakdong River. M. aeruginosa blooms can be suppressed by employing an integrated water resource management program that accommodates meteo-hydrological factors along with the effective control of exogenous nutrient sources.

Electricity generation and nutrients removal from high-strength liquid manure by air-cathode microbial fuel cells

ABSTRACTAir-cathode microbial fuel cells (MFCs) are widely tested to recover electrical energy from waste streams containing organic matter. When high-strength wastewater, such as liquid animal manure, is used as a medium, inhibition on anode and cathode catalysts potentially impairs the effectiveness of MFC performance in power generation and pollutant removal. This study evaluated possible inhibitive effects of liquid swine manure components on MFC power generation, improved liquid manure-fed MFCs performance by pretreatment (dilution and selective adsorption), and modeled the kinetics of organic matter and nutrients removal kinetics. Parameters monitored included pH, conductivity, chemical oxygen demand (COD), volatile fatty acids (VFAs), total ammoniacal nitrogen (TAN), nitrite, nitrate, and phosphate concentrations. The removals of VFA and TAN were efficient, indicated by the short half-life times of 4.99 and 7.84 d, respectively. The mechanism for phosphate decrease was principally the salt precipitation on cathode, but the removal was incomplete after 42-d operation. MFC with an external resistor of 2.2 kΩ and fed with swine wastewater generated relatively small power (28.2 μW), energy efficiency (0.37%) and Coulombic efficiency (1.5%). Dilution of swine wastewater dramatically improved the power generation as the inhibitory effect was decreased. Zeolite and granular activated carbon were effective in the selective adsorption of ammonia or organic matter in swine wastewater, and so substantially improved the power generation, energy efficiency, and Coulombic efficiency. A smaller external resistor in the circuit was also observed to promote the organic matter degradation and thus to shorten the treatment time. Overall, air-cathode MFCs are promising for generating electrical power from livestock wastewater and meanwhile reducing the level of organic matter and nutrients.

Effect of phosphate on U(VI) sorption to montmorillonite: Ternary complexation and precipitation barriers

Phosphate addition is a potential treatment method to lower the solubility of U(VI) in soil and groundwater systems by causing U(VI) phosphate precipitation as well as enhancing adsorption. Previous work has shown that iron oxide surfaces may facilitate the nucleation of U(VI) phosphate minerals and, that under weakly acidic conditions, phosphate also enhances U(VI) adsorption to such phases. Like iron oxides, clays are important reactive phases in the subsurface but little is known about the interaction of U(VI) and phosphate with these minerals. The effect of aqueous phosphate on U(VI) binding to Wyoming montmorillonite (SWy-2) in air-equilibrated systems was investigated. Equilibrium U(VI) uptake to montmorillonite was determined at pH 4, 6 and 8 at discrete initial phosphate concentrations between 0 and 100μM. The observed behavior of U(VI) indicates a transition from adsorption to precipitation with increasing total uranium and phosphate concentrations at all pH values. At the highest phosphate concentration examined at each pH value, a barrier to U(VI) phosphate nucleation is observed. At lower concentrations, phosphate has no effect on macroscopic U(VI) adsorption. To assess the mechanisms of U(VI)-phosphate interactions on smectite surfaces, U(VI) speciation was investigated under selected conditions using laser-induced fluorescence spectroscopy (LIFS) and extended X-ray absorption fine-structure (EXAFS) spectroscopy. Samples above the precipitation threshold display EXAFS and LIFS spectral signatures consistent with the autunite family of U(VI) phosphate minerals. However, at lower U(VI) concentrations, changes in LIFS spectra upon phosphate addition suggest that U(VI)-phosphate ternary surface complexes form on the montmorillonite surface at pH 4 and 6 despite the lack of a macroscopic effect on adsorption. The speciation of solid-associated U(VI) below the precipitation threshold at pH 8 is dominated by U(VI)-carbonate surface complexes. This work reveals that ternary complexation may occur without a macroscopic signature, which is attributed to phosphate not appreciably binding to smectite in the absence of U(VI), with U(VI) surface complexes serving as the sole reactive surface sites for phosphate. This study shows that phosphate does not enhance U(VI) adsorption to smectite clay minerals, unlike oxide phases, and that a barrier to homogeneous nucleation of U(VI) phosphates was not affected by the presence of the smectite surface.