Simultaneous microbial removal of carbon,nitrogen, and phosphorus in a modified anaerobic/aerobic (A/O) bioreactor with no phosphorus release

A modified anaerobic/aerobic (A/O) bioreactor that simultaneously removed carbon, nitrogen ( ‐N) and phosphorus ( ‐P) was continuously run and debugged. After 34 days of reactor operation, the removal efficiencies of ‐N, carbon (glucose) and ‐P reached 99.26, 95.81 and 94.35%, respectively. Notably, the ammonium removal with no accumulation of nitrite ( ‐N) and nitrate ( ‐N) in the anaerobic part supported the occurrence of simultaneous nitrification and denitrification and no ‐P was released during the removal process of phosphorus. Moreover, the principal component analysis and response surface methodology based on the Box–Behnken design were applied to determine the optimal removal conditions for volatile suspended solids (VSS) (335 mg/L), ‐N (60 mg/L), glucose (900 mg/L) and pH (7). Finally, phylogenetic analysis of the bacterial consortium was conducted by denaturing gradient gel electrophoresis, which demonstrated that Clostridium and Proteobacteria were the potential functional groups in the anaerobic tank of the A/O bioreactor.     

Full‐scale maturation ponds working below a latitude of 43°S in a semiarid area: seasonal performance and removal mechanisms

Stabilisation ponds are the most frequently used wastewater treatment technology in Argentina. This study focuses on the performance of two maturation ponds (MPs) that are part of the full‐scale sewage treatment system of Puerto Madryn. Seventy‐seven shots of surface water were analysed for organic matter, inorganic nitrogen, phytoplankton dynamics and bacterial removal. The system presented a clear evolution with respect to oxygenation and phytoplankton development. The treated wastewater reached values above 8 mg‐O₂/L, an important organic matter removal, and this was accompanied by a strong increase in pH. removal and oxidation, was active even during winter in the MPs, with average concentrations below 10 mg ‐ /L. Bacteriological removal resulted in a liquid that approached the WHO recommendations for unrestricted irrigation. These results show that is possible to generate treated wastewater in stabilisation ponds working in a semiarid and temperate region, with bacterial content and conductivity suitable for irrigation.     

A study of external mass transfer effect on biodegradation of phenol using low‐density polyethylene immobilized Bacillus flexus GS1 IIT (BHU) in a packed bed bioreactor

The impact of external mass transport on the biodegradation rate of phenol in a packed bed bioreactor (PBBR) was studied. A potential bacterial species, Bacillus flexus GS1 IIT (BHU), was isolated from the petroleum‐contaminated soil. Low‐density polyethylene (LDPE) immobilized with the B. flexus GS1 IIT (BHU) was used as packing material in the PBBR. The PBBR was operated by varying the inlet feed flow rate from 4 to 10 mL/min, and the corresponding degradation rate coefficients were found to be in the range of 0.119–0.157 L/g h. In addition, the highest removal rate of phenol was obtained to be 1.305 mg/g h at an inlet feed rate of 10 mL/min. The external mass transfer was studied using the model . A new empirical correlation for the biodegradation of phenol in the PBBR was developed after the evaluation at various values of K and n.     

Improved dewaterability of sewage sludge by Fe(II)‐activated persulfate oxidation combined with polymers

The combination of Fe(II)‐activated persulfate oxidation with polymers potentially applied to enhance sludge dewaterability was investigated in this work. The experiments mainly concentrated on their efficacies and the optimization of the major operational parameters. The results showed that the combination was efficient, especially when polyaluminium chloride (PAC) and chitosan were used as polymers. The optimal conditions of this process under experimental conditions were at = 50 mg/g (dry solids), = 125 mg/g, reaction time = 20 min, PAC = 125 mg/g and chitosan = 100 mg/g, under which the specific resistance to filtration (SRF) with a reduction efficiency of 94.87% was achieved.     

Environmental variables and benthic macroinvertebrate assemblage in the headwater streams of an Afro‐tropical reservoir

The assemblage of benthic macroinvertebrates in relation to some selected environmental variables of the two headwater streams of Aiba Reservoir was studied from May 2013 to March 2014. This was with a view to assessing the health status and water quality of the streams, and comparing their taxa richness with similar studies on the reservoir and its out‐flowing stream. A total of 23 taxa were recorded in the study. and showed indirect relationships (P < 0.05) with bioindicators of good water quality, while dissolved oxygen (DO) showed indirect relationship (P < 0.05) with bioindicators of poor water quality. The streams were of poor biological water quality, and diversity indices revealed that they were polluted and unstable in habitat structure. Anthropogenic impacts at the upper reaches need to be mitigated and regular biomonitoring of the streams is of the essence, in order to conserve the integrity of the downstream reservoir.     

Combining magnesium ammonium phosphate precipitation with membrane processes for ammonia removal from methanogenic leachates

Chemical precipitation of ammonia as magnesium ammonium phosphate (MAP) from methanogenic leachates can be a competitive alternative to biological ammonia removal. Potential for trading of the precipitate as a fertiliser defines the economics of the process. The precipitate from a landfill leachate often containing organics and heavy metals as impurities with unknown risks limits its possibility for agricultural use. This study combines MAP precipitation with membrane processes and investigates the influence of wastewater matrix, solution pH and dosage ratio of chemicals (Mg²⁺ : ) on the precipitate purity through lab scale semibatch experiments. Under similar experimental conditions (pH 8.5 and 1 : 1 Mg²⁺ : molar dosage), the precipitates from raw leachate and nanofiltration (NF) permeate showed MAP contents of 65 and 90%, respectively, correspondingly with about 8300 and 1600 mg TOC/kg_precipitate. For precipitation from NF permeate, precipitation at pH 8.0 with 1 : 1 dosage ratio and pH 8.5 with 1 : 0.9 dosage ratio gave precipitates each with about 97% purity.     

Removal of endosulfan in a sequencing batch reactor: addition of granular activated carbon as improvement strategy

A granular activated carbon‐sequencing batch reactor (GAC‐SBR) was used to assess the removal of organochlorine endosulfan pesticide. The reactor operated in three stages: (I) starter and stabilization; (II) addition of 4 mg/L of endosulfan in feed; and (III) a single addition of 1 g/L of GAC to mixed liquor. During the 249 days of operation, the removal efficiency of COD was 96 ± 2%; for ‐N 72 ± 1%; and for PO₄^?3‐P 48 ± 13%. Was eliminated the 79% of endosulfan in stage II and 99% in stage III, not found its metabolite (endosulfan sulphate) in the reactor effluent. A consortium of eight bacterial strains was identified in the reactor stages, assessing five of them in the presence of 4 mg endosulfan/L by growth kinetics. According to the results, the joint action of the consortium and GAC addition is the responsible of eliminating the pesticide.     

Sewage sludge conditioning by Fe(II)‐activated persulphate oxidation combined with skeleton builders for enhancing dewaterability

In this study, a joint application of Fe(II)‐activated persulphate oxidation and skeleton builders is used to condition sewage sludge for subsequent dewatering. The study mainly focuses on their efficacies and the optimization of the major operational parameters. The experimental results show that the joint application for conditioning sewage sludge is effective, especially using lime and ordinary Portland cement (OPC) as skeleton builders. Additionally, it is revealed that Fe(II)‐activated persulphate oxidation needs sufficient reaction time (20 min) to degrade organics in the sludge. The optimal conditions of this process are at Fe²⁺ = 47.6 mg g^?1 (dry solids), S₂ = 119.1 mg g^?1, lime = 446.4 mg g^?1, and OPC = 297.6 mg g^?1, under which the water content of dewatered sludge cake is 54.8% and the specific resistance to filtration (SRF) is 4.3 × 10¹¹ m kg^?1 with a reduction efficiency of 96.6%.     

The effects of road salt application on the accumulation and speciation of cations and anions in an urban environment

This study aimed to assess the quality of road runoff in heavy traffic and residential areas of Hamedan province, in the western region of Iran. To investigate the effects of salt pollution, 14 runoff samples were collected from streets during the winter and spring of 2009. Streets received different amounts of deicing salt depending on the traffic density. Results showed that deicing salt has major affects on sodium (Na⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl^?), bicarbonate (), sulfate () and phosphate () pollution. This is important because this type of watercourse contamination can lead to serious problems, such as eutrophication. We also found an increase in lead (Pb²⁺) concentration, which was not attributable to the application of deicing agents, but that was due to the combustion of leaded gasoline. Speciation of Ca, Mg, Pb and P chemical species in the samples was calculated using Visual Minteq 2.6 program. The results indicated that Ca and Mg were mainly present as free ions, Pb was mainly present as PbCO₃ (aq), while the dominant P species were and .     

Carbon dioxide emission and its regulation at land–water interface downstream of a point source at Ganga River (India)

The streams and rivers are considered hotspots of CO₂ exchange; and representative direct CO₂ emission measurements are essential for a correct regional estimate. We measured CO₂ emission flux at 15 sites at land–water interface downstream of a point source during low flow for three consecutive months for the year 2017. The general range of CO₂ efflux observed here was close to the results of regional studies, although values near the point source were disproportionately high (>350 mg/m²/h). CO₂ emission flux showed strong dependence on total organic carbon (TOC; R² = 0.96; P < 0.001), (R² = 0.88; P < 0.001), soluble reactive‐P (SRP; R² = 0.91; P < 0.001) and microbial activity measured in terms of fluorescein diacetate activity (FDAase; R² = 0.92; P < 0.001) and substrate induced respiration (SIR; R² = 0.96; P < 0.001). Because point source‐associated interfaces provide heterogeneous habitats, our study suggests the need for large scale monitoring of CO₂ emission at land–water interface of major rivers for more correctly presenting the regional scale CO₂ budget.     

A mixing‐length‐scale‐based analytical model for predicting velocity profiles of open‐channel flows with submerged rigid vegetation

In open‐channel flows with submerged vegetation, the vertical velocity profile can often be described by two layers: the vegetation layer in the lower region and the surface layer in the upper non‐vegetated region. In this paper, a new mixing‐length scale of eddy is proposed for predicting the vertical velocity profile of flow in an open‐channel with submerged rigid vegetation. The analytical model of velocity profile is based on the momentum equation of flow where the turbulent eddy viscosity is assumed to have a linear relationship with the local velocity. The proposed model was tested against different datasets from the literature. The 22 datasets used cover a range of submergence [flow depth (H)/vegetation height (h) = 1.25 ~ 3.38], different vegetation densities of ah = 0.11 ~ 1.85 (a defined as the frontal area of the vegetation per unit volume) and bed slopes (S_o = 1.8 × 10^?6 ~4.0 × 10^?3). This study showed that the proposed model can predict the velocity profiles well against all datasets, and that the mixing length scale of eddies (λ) is well related with both vegetation height (h) and flow depth of surface layer (i.e. the height of non‐vegetation layer, H–h). Close examination of λ in the proposed model showed that when λ = 0.03, the model predicts vertical velocity profiles well for all datasets used except for very shallow submergence (i.e. H/h < 1.5).     

Strain gradient effects on flexural strength design of normal‐strength concrete beams

In the flexural strength design of normal‐strength concrete (NSC) beams, the resultant concrete force and its centroid within the compression zone is generally expressed in an equivalent rectangular stress block. The equivalent concrete stress is expressed as , where is the uni‐axial concrete cylinder strength. Currently, the value of α stipulated in various design codes for NSC is taken as 0.85. Nonetheless, in an experimental study conducted earlier by the authors on NSC columns subjected to concentric and eccentric axial loads, it was found that the value of α significantly depends on strain gradient, which generally increases as strain gradient increases until it reaches a maximum value. Therefore, strain gradient is a critical factor and should be considered in the flexural strength design of NSC members. In this paper, a new flexural strength design method that incorporates the effects of strain gradient is developed for NSC beams. An equivalent rectangular concrete stress block, which is strain‐gradient dependent, is proposed and applied to produce a set of equations for the flexural strength design of singly and doubly reinforced NSC beams with various concrete strengths. Lastly, these equations are converted into charts for practical design application. Copyright © 2010 John Wiley & Sons, Ltd.     

Nitrate removal from water using zero‐valent aluminium

Nitrate pollution in surface and groundwater is known to adversely affect human health, water quality and the health of aquatic ecosystems. Zero‐valent aluminium is a strong reductant for ions such as nitrate. In this study, its use in nitrate reduction efficiency was evaluated as a function of pH, aluminium dosage and aluminium particle size through a lab‐scale investigation. The most effective pH for complete nitrate removal, with an initial concentration of 14.0 ± 1.0 mg N/L, was found to be 13 ± 0.2. Under this condition, complete removal was achieved in 5 min, using aluminium particle size of 1–3 µm and aluminium‐to‐nitrate (NO₃^–‐N) ratio of 125. The 1–3 µm and 297–841 µm aluminium particles removed nitrate at a reaction rate constant (k) of 0.048 ± 0.017 (mg‐N/L)^1.53/min and at 0.042 ± 0.014 (mg‐N/L)^1.28/min, respectively. The use of smaller aluminium particles was found to be more effective for nitrate removal than large particles, and it was observed that for these particle sizes, aluminium dosages was less of a factor than any other experimental conditions evaluated.     

Skin squames contribute to ammonia and volatile fatty acid production from bacteria colonizing in air‐cooling units with odor complaints

One of the most notable Indoor Air Quality problems is odor emission. This study investigated the potential contribution of skin squames to the production of ammonia (NH₃) and volatile organic acids (VFAs) by 7 bacteria isolated from air‐cooling (AC) units with complaints of urine and body odors. Our previous study showed that keratinolytic activity is higher in AC units with odor complaints than those without. In the offices where these units are located, the most likely source of keratins is from human skin squames. Most bacteria can produce NH₃ and VFAs in the skin squame culture. Some correlations between the levels of NH₃, , VFAs, and keratinolytic activity were found. The odor production pathway with skin squames was proposed. Staphylococcus haemolyticus was abundant in the AC units with odor problems and had a high level of keratinolytic activity in addition to odor production. For long‐term odor control, it is important to reduce the level of skin squames entering the AC units.     

A quantitative property‐property relationship for the internal diffusion coefficients of organic compounds in solid materials

Indoor releases of organic chemicals encapsulated in solid materials are major contributors to human exposures and are directly related to the internal diffusion coefficient in solid materials. Existing correlations to estimate the diffusion coefficient are only valid for a limited number of chemical‐material combinations. This paper develops and evaluates a quantitative property‐property relationship (QPPR) to predict diffusion coefficients for a wide range of organic chemicals and materials. We first compiled a training dataset of 1103 measured diffusion coefficients for 158 chemicals in 32 consolidated material types. Following a detailed analysis of the temperature influence, we developed a multiple linear regression model to predict diffusion coefficients as a function of chemical molecular weight (MW), temperature, and material type (adjusted R² of .93). The internal validations showed the model to be robust, stable and not a result of chance correlation. The external validation against two separate prediction datasets demonstrated the model has good predicting ability within its applicability domain (>.8), namely MW between 30 and 1178 g/mol and temperature between 4 and 180°C. By covering a much wider range of organic chemicals and materials, this QPPR facilitates high‐throughput estimates of human exposures for chemicals encapsulated in solid materials.     

Lead removal from groundwater by granular mixtures of pumice,perlite and lime using permeable reactive barriers

Permeable Reactive Barrier (PRB) is an in situ technology for remediation of contaminated groundwater. This article presents results of studies on three granular mixtures were used for remediation of lead (Pb²⁺) contaminated groundwater using PRBs. The mixtures were composed of pumice, perlite and lime in different proportions. Several column experiments were conducted for evaluation of performance of the mixtures for lead removal. The experiments were carried out for over 50 days to evaluate the long‐term performance of the PRBs. It was found out that pumice‐perlite mixture with a weight proportion of 1 : 1 and pumice‐lime‐perlite mixture with a weight proportion of 2 : 2 : 1 can be used as effective reactive media for lead removal. The removal efficiency of the proposed mixtures was 99.9%. The permeability of the reactive media was relatively constant over 53 days continuous experiments and the results demonstrated that the mentioned mixtures have acceptable performance to maintain hydraulic conductivity of PRBs.     

A Modified Sliding Mode Fault Tolerant Control for Large‐Scale Civil Infrastructure

Adaptable active control strategies besides advance sensors and actuators technologies lead to higher performance of vibrational control in civil infrastructures under severe ground motions. These resilience control systems are robust against model uncertainties as well as being online recoverable from the malfunctioning of sensors and actuators. In this study, resilient control system based on sliding mode (SM) fault detection observer and SM fault tolerant control is improved for actuator fault in large‐scale systems. The SM fault detection observer is modified for eliminating the excessive chattering in estimating states and actuators’ fault, and the reconfigurable SM fault tolerant control is improved to minimizing input forces in control framework under seismic action. Design of observer and controller is performed using linear matrix inequalities. Numerical simulations on the cable‐stayed bridge benchmark demonstrate the effectiveness of the proposed fault‐tolerant system. Despite the high order of this large‐scale structure, the proposed fault detection and diagnosis method can effectively find the location and size of faults in actuators without performance degradation and computational costs. The fault‐tolerant controller maintains the performance of the structure at an acceptable level in the post‐fault case by redistribution of control signal to actuators.     

Biodegradation of monoaromatic hydrocarbons in aquifer columns amended with hydrogen peroxide and nitrate

The ability of indigenous microorganisms to degrade benzene, toluene, ethylbenzene and xylenes (BTEX) in laboratory scale flow-through aquifer columns was tested separately with hydrogen peroxide (110 mg/l) and nitrate (330 mg/l as NO₃⁻) amendments to air-saturated influent nutrient solution. The continuous removal of individual components from all columns relative to the sterile controls provided evidence for biodegradation. In the presence of hydrogen peroxide, the indigeneous microorganisms degraded benzene and toluene (> 95%), meta- plus para-xylene (80%) and ortho-xylene (70%). Nitrate addition resulted in 90% removal of toluene and 25% removal of ortho-xylene. However, benzene, ethylbenzene, meta- and para-xylene concentrations were not significantly reduced after 42 days of operation. Following this experiment, low dissolved oxygen (< 1 mg/l) conditions were initiated with the nitrate-amended column influent in order to mimic contaminated groundwater conditions distal from a nutrient injection well. Toluene continued to be effectively degraded (> 90%), and more than 25% of the benzene, 40% of the ethylbenzene, 50% of the meta- plus para-xylenes and 60% of the ortho-xylene were removed after several months of operation.     

响应面法优化电解芬顿协同法深度处理老龄垃圾渗滤液

采用电解芬顿法深度处理老龄垃圾渗滤液,选取电量、进水 pH 值、进水氨氮浓度3个因素为变量,CODCr 去除率为响应值进行 Box-Behnken 中心组合设计。利用响应面法对试验结果进行分析,建立了 CODCr 去除率为响应值的二阶多项式模型并进行了方差分析和显著性检验,通过解模型逆矩阵得到最佳条件：单位面积电量为23．26 Ah／dm2、pH 值为3．58、进水氨氮浓度56．78 mg／L。在最佳条件下,CODCr 去除率为96．5％,与模型预测值偏差为4．45％,吻合度较高。对电解芬顿深度处理前后的渗滤液进行 GC-MS 分析,表明电解芬顿协同处理技术能有效降解垃圾渗滤液中难生化降解的有机物,将有机物种类从42种降低至21种,是较有效的深度处理技术。     

Enhanced electrocoagulation–electroflotation for turbidity removal by Opuntia ficus indica cladode mucilage

The optimisation of the electrocoagulation‐electroflotation (EC‐EF) process assisted by the mucilage of the Opuntia ficus indica (OFI), on the turbidity removal was performed through the response surface methodology (RSM). For a solution of 300 mg/L of silica gel, high turbidity removal (93.14% ± 1.31) was obtained under the optimal conditions of 2.5 mg/L, 21.2 V, 9.65 and 2.61 mS/cm for the mucilage concentration, voltage, pH and conductivity, respectively, this experimental value was close to the predicted value of 92.96% ± 0.3. OFI mucilage increases turbidity removal efficiency and reduces specific energy consumption at a fixed current density. The turbidity removal of the EC‐EF process was improved by 30.94% compared with the conventional EC–EF (EC–EF without OFI mucilage) which shows 62.02% ± 1.45 of turbidity removal.