Efficient removal of Al(Ⅲ)and P507 from high concentration MgCl_(2)solution based on in-situ reaction strategy

For a highly efficient recycling of a wastewater containing a high concentration of MgCl_(2),Al(Ⅲ)and P507 were scheduled to be removed in advance.In this study,the in-situ removal of Al(Ⅲ)and P507 from a high concentration MgCl_(2)solution at different pH values and Al/P molar ratios was investigated.The results showed that P507 formed organic complexes of Al_(x)(OH)_y^(Z+)-P507 at pH of 2.0-4.0.At pH of 4.0-5.0,Al(Ⅲ)precipitated and transferred into Al(OH)_(3)with a flocculent amorphous morphology.Active sites on the Al(OH)_(3)surface enhanced the removal efficiency of P507.At pH of 6.0-6.5,Al(Ⅲ)and Mg(Ⅱ)formed layered crystalline Al(OH)_(3)and MgAl_(2)(OH)_(8with)small pore channels and fewer active sites,resulting in a reduced removal efficiency of P507.When the Al/P molar ratio exceeded 13 and the pH was between 4.0 and 5.0,the removal rates of both Al(Ⅲ)and P507 were higher than98%,while the concentration loss of Mg(Ⅱ)was only 0.2%-0.9%.

Approach to estimating non-point pollutant load removal rates based on water environmental capacity: a case study in Shenzhen

An innovative approach based on water environmental capacity for non-point source NPS pollution removal rate estimation was discussed by using both univariate and multivariate data analysis.Taking Shenzhen city as the study case a 67% to 74% NPS pollutant load removal rate can lead to meeting the chemical oxygen demand COD pollution control target for most watersheds.In contrast it is hardly to achieve the ammonia nitrogen NH4-N total phosphorus TP and biological oxygen demand BOD5 pollution control target by simply removing NPS pollutants. This highlights that the pollution control strategies should be taken according to different pollutant species and sources in different watersheds rather than one-size-fits-all .

IMPROVING MATERIAL REMOVAL RATE OF BRITTLE CERAMICS THROUGH HONING INCIDENTAL TENSILE STRESSES

The stress intensity factors and stress conditions of machining cracks are analyzed by fracture mechanics on the basis of honing characteristics and of brittle ceramic mechanical behavior.Because the honing incidental tensile stresses effectively decrease the critical grinding stresses and increase the stress intensity factors of machining cracks,the honing process can be carried out easily.The results show that honing can be an efficient machining method for brittle materials.

Material Removal Rate Prediction of Electrical Discharge Machining Process Using Artificial Neural Network

This article presents an Artificial Neural Network （ANN） architecture to model the Electrical Discharge Machining （EDM） process. It is aimed to develop the ANN model using an input-output pattern of raw data collected from an experimental of EDM process, whereas several research objectives have been outlined such as experimenting machining material for selected gap current, identifying machining parameters for ANN variables and selecting appropriate size of data selection. The experimental data （input variables） of copper-electrode and steel-workpiece is based on a selected gap current where pulse on time, pulse off time and sparking frequency have been chosen at optimum value of Material Removal Rate （MRR）. In this paper, the result has significantly demonstrated that the ANN model is capable of predicting the MRR with low percentage prediction error when compared with the experimental result.

On investigating the soda-lime shot blasting of AZ31 alloy:Effects on surface roughness,material removal rate,corrosion resistance,and bioactivity

In the present study,a novel method of surface finish improvement is proposed using shot blasting of soda lime(SBSL)beads on the Mg-AZ31 alloy.The effect of the soda blasting process parameters,such as blast pressure,stand-off distance,and blast duration,have been studied in-response of material removal rate(MRR)and surface roughness(SR)and corresponding statistical models have been obtained.The multi-objective optimization has also been performed to obtain parameters for maximum MRR and minimum SR.The corrosion behavior of the treated specimens has been performed to study their in-vitro biodegradability in simulated body fluid(SBF)for 1,3,7,10,15,and 21 days.The wettability study of the SBSL treated samples has been investigated using sessile drop methodology.Further,cell adhesion test has also been performed to study the biocompatibility characteristics of the SBSL treated samples using Huh7 liver cell lines.Based on obtained quantitative data as well as scanning electron microscopy analysis of treated samples,the SBSL treatment of the AZ31 alloy has been found highly useful in producing biocompatibility surfaces along with desirable morphological features.

Nitrogen removal efficiency of iron-carbon micro-electrolysis system treating high nitrate nitrogen organic pharmaceutical wastewater

The nitrate nitrogen removal efficiency of iron-carbon micro-electrolysis system was discussed in treating pharmaceutical wastewater with high nitrogen and refractory organic concentration. The results show that the granularity of fillings,pH,volume ratios of iron-carbon and gas-water,and HRT. have significant effects on the nitrogen removal efficiency of iron-carbon micro-electrolysis system. The iron-carbon micro-electrolysis system has a good removal efficiency of pharmaceutical wastewater with high nitrogen and refractory organic concentration when the influent TN,NH4+-N,NO3--N and BOD5/CODCr are 823 mg/L,30 mg/L,793 mg/L and 0.1,respectively,at the granularity of iron and carbon 0.425 mm,pH 3,iron-carbon ratio 3,gas-water ratio 5,HRT 1.5 h,and the removal rates of TN,NH4+-N and NO3--N achieve 51.5%,70% and 50.94%,respectively.

Effect of mechanical anisotropy on material removal rate and surface quality during polishing CdZnTe wafers

The mechanical characters of CdZnTe crystal were investigated by nanoscratch tests, and the effects of mechanical anisotropy on the material removal rate and surface quality were studied by polishing tests. There is a peak of frictional coefficient at the early stage of scratch, and increasing the vertical force will result in the increase of peak value correspondingly. The fluctuation phenomenon of frictional coefficient is generated at high vertical force. The lateral forces show the apparent twofold and threefold symmetries on （110） and （111） planes, respectively. To obtain high surface quality, low polishing pressure and hard direction （〈 T10 〉 directions on （110） plane and 〈 112 〉 directions on （111） plane） should be selected, and to achieve high material removal rate, high polishing pressure and soft direction （〈001〉 directions on （110） plane and 〈 121 〉 directions on （111） plane） should be selected.

Effect of carbon source and nitrate concentration on denitrifying phosphorus removal by DPB sludge

Effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by DPB sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in anoxic phase increased with the high initial anaerobic carbon source addition. However once the initial COD concentration reached a certain level, which was in excess to the PHB saturation of poly-P bacteria, residual COD carried over to anoxic phase inhibited the subsequent denitrifying phosphorus uptake. Simultaneously, phosphate uptake continued until all nitrate was removed, following a slow endogenous release of phosphate. High nitrate concentration in anoxic phase increased the initial denitrifying phosphorus rate. Once the nitrate was exhausted, phosphate uptake changed to release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the denitrificaion and anoxic phosphorus uptake operations.

Denitrifying phosphorus removal in a step-feed CAST with alternating anoxic-oxic operational strategy

A bench-scale cyclic activated sludge technology （CAST） was operated to study the biological phosphorus removal performance and a series of batch tests was carried out to demonstrate the accumulation of denitrifying polyphosphate-accumulating organisms （DNPAOs） in CAST system. Under all operating conditions, step-feed CAST with enough carbon sources in influent had the highest nitrogen and phosphorus removal efficiency as well as good sludge settling performance. The average removal rate of COD, NH4^＋-N, PO4^3--P and total nitrogen （TN） was 88.2%, 98.7%, 97.5% and 92.1%, respectively. The average sludge volume index （SVI） was 133 mL/g. The optimum anaerobic/aerobic/anoxic （AOA） conditions for the cultivation of DNPAOs could be achieved by alternating anoxic/oxic operational strategy, thus a significant denitrifying phosphorus removal occurred in step-feed CAST. The denitrification of NO^x--N completed quickly due to step-feed operation and enough carbon sources, which could enhance phosphorus release and further phosphorus uptake capability of the system. Batch tests also proved that polyphosphate-accumulating organisms （PAOs） in the step-feed process had strong denitrifying phosphorus removal capacity. Both nitrate and nitrite could be used as electron acceptors in denitrifying phosphorus removal. Low COD supply with step-feed operation strategy would favor DNPAOs accumulation.

Novel strategy of nitrogen removal from domestic wastewater using pilot Orbal oxidation ditch

A pilot-scale Orbed oxidation ditch was operated for 17 months to optimize nitrogen removal from domestic wastewater of average COD to total nitrogen ratio of 2.7, with particular concern about the roles of dissolved oxygen （DO）, mixed liquor suspended solids （MLSS） and return activated sludge （RAS） recycle ratio. Remarkable simultaneous nitrification and denitrification （SND） was observed and mean total nitrogen （TN） removal efficiency up to 72.1% was steadily achieved, at DO concentration in the out, middle and inner channel of 0.1, 0.4 and 0.7 mg/L, respectively, with an average M LSS of 5.5 g/L and RAS recycle ratio of 150%. Although the out channel took the major role in TN removal, the role of middle channel should never be ignored. The denitrification potential could be fully developed under low DO, high MLSS with adequate RAS ratio. The sludge settleability was amazingly improved under low DO operation mode, and some explanations were tried. In addition, a scries of simplified batch tests were done to determine whether novel microorganisms could make substantial contribution to the performance of nitrogen removal. The results indicated that the SND observed in this Orbal oxidation ditch was more likely a physical phenomenon.

Enhanced removal of nitrate and phosphate from wastewater by Chlorella vulgaris: Multi-objective optimization and CFD simulation

To enhance the efficiency of wastewater biotreatment with microalgae, the effects of physical parameters need to be investigated and optimized. In this regard, the individual and interactive effects of temperature, p H and aeration rate on the performance of biological removal of nitrate and phosphate by Chlorella vulgaris were studied by response surface methodology(RSM). Furthermore, a multi-objective optimization technique was applied to the response equations to simultaneously find optimal combinations of input parameters capable of removing the highest possible amount of nitrate and phosphate. The optimal calculated values were temperature of 26.3 °C, pH of 8 and aeration rate of 4.7 L·min^(-1). Interestingly, under the optimum condition, approximately 85% of total nitrate and 77% of whole phosphate were removed after 48 h and 24 h, respectively, which were in excellent agreement with the predicted values. Finally, the effect of baffle on mixing performance and, as a result, on bioremoval efficiency was investigated in Stirred Tank Photobioreactor(STP) by means of Computational Fluid Dynamics(CFD). Flow behavior indicated substantial enhancement in mixing performance when the baffle was inserted into the tank. Obtained simulation results were validated experimentally. Under the optimum condition, due to proper mixing in baffled STP, nitrate and phosphate removal increased up to 93% and 86%,respectively, compared to unbaffled one.

Removal of copper from molybdenite concentrate by mesophilic and extreme thermophilic microorganisms

Mixed mesophilic and extreme thermophilic bioleaching were evaluated to remove copper from the molybdenite concentrate.Bioleaching tests were carried out in shake flasks and in a 50-L bioreactor.The shake flask tests were performed with different inoculum size,solids density,pH.and temperature in order to identify optimum conditions.The highest amount of copper elimination,75%was obtained with extreme thermophilic microorganisms(at 12%inoculation,10%solids,65℃and a pH of 1.5).The highest copper elimination by mesophilic microorganisms was 55%(at 12%inoculation,5%solids,30℃at pH 2).The optimum conditions in shake flask tests were applied to 7 days batch tests in a50-L bioreactor.Extreme thermophilic experiment gave the best copper elimination of 60%(at 12%inoculation,10%solids,65℃and pH 1.5).Mesophilic test removed 50%of the copper(at 12%inoculation,10%solids,35℃at pH 2).

Enhanced biological nutrients removal using an integrated oxidation ditch with vertical circle from wastewater by adding an anaerobic column

Compared to conventional oxidation ditches, an integrated oxidation ditch with vertical circle （IODVC） has the characters of concise configuration, simple operation and maintenance, land saving and automatical sludge returning. By the utilization of vertical circulation, an aerobic zone and an anoxic zone can be unaffectedly formed in the IODVC. Therefore, COD and nitrogen can be efficiently removed. However, the removal efficiency of phosphorus was low in the IODVC. In the experiment described, a laboratory scale system to add an anaerobic column to the IODVC has been tested to investigate the removal of phosphorus from wastewater. The experimental results showed that the removal efficiency of TP with the anaerobic column was increased to 54.0% from 22.3% without the anaerobic column. After the acetic sodium was added into the influent as carbon sources, the mean TP removal efficency of 77. 5 % was obtained. At the same time, the mean removal efficiencies of COD, TN and NH3-N were 92.2%, 81.6% and 98.1%, respectively, at 12 h of HRT and 21-25 d of SRT. The optimal operational conditions in this study were as follows： recycle rate = 1.5-2.0, COD/TN 〉 6, COD/TP 〉 40, COD loading rate = 0.26-0.32 kgCOD/（kgSS· d）, TN loading rate = 0. 028-0. 034 kgTN/（ kgSS·d） and TP loading rate = 0.003-0.005 kgTP/（kgSS· d）, respectively.

Removal Rate of Phosphorus by Different Constructed Wetland Substrates

[ Objective] The study aimed to discuss the removal rate of phosphorus by different constructed wetland substrates. [ Methed] Based on static experiments, we analyzed the removal rate and characteristics of phosphorus by different constructed wetland substrates like steel slag, cin- der slag, shale, boiler slag, soil and gravel. [ Result~ The maximum adsorption of phosphorus by various substrates showed as follows, steel slag 〉 cinder slag 〉 shale 〉 boiler slag 〉 soil 〉 gravel. When the initial concentration of phosphorus was 5 mg/L, the removal rate of phosphorus by the steel slag, cinder slag, shale, boiler slag, soil and gravel was 99.76%, 85.8%, 71.2%, 63.0%, 46.8% and 11.7% respectively. It is suggested that shale and boiler slag can be used as the substrate of subsurface-flow constructed wetlands; cinder slag can be chosen as a renewable sub- strate for intensifying phosphorus removal; steel slag could be used at the end of subsurface-flow constructed wetlands for treating TP in outflows. [Concluslon] The research could provide theoretical references for choosing a suitable substrate for constructed wetlands to remove phosphorus in future.

Removal of high concentrated ammonia nitrogen from landfill leachate by landfilled waste layer

The landfill of municipal solid waste(MSW) could be regarded as denitrification reactor and involved in ammonia nitrogen biological removal process. In this research, the process was applied to municipal solid waste collected in Shanghai, China, which was characterized by high food waste content. The NH + 4 removal efficiency in the system of SBR nitrifying reactor followed by fresh and matured landfilled waste layer in series was studied. In the nitrifying reactor, above 90% of NH + 4 in leachate was oxidized to NO - 2 and NO - 3. Then high concentrated NO - 2 and NO - 3 were removed in the way of denitrification process in fresh landfilled waste layer. At the same time, degradation of fresh landfilled waste was accelerated. Up to the day 120, 136.5 gC/(kg dry waste) and 17.9 gN/(kg dry waste) were converted from waste layer. It accounted for 50.15% and 86.89% of the total carbon and nitrogen content of preliminary fresh waste, which was 4.42 times and 5.17 times higher than that of reference column respectively. After filtering through matured landfilled waste, BOD 5 concentration in leachate dropped to below 100 mg/L, which would not affect following nitrification adversely. Because the matured landfilled waste acted as a well methanogenic reactor, 23% of carbon produced accumulatively from fresh landfilled waste degradation was converted into CH 4.

Study of control strategy and simulation in anoxic-oxic nitrogen removal process

The control strategy and simulation of external carbon addition were specially studied in an anoxic-oxic(A/O) process with low carbon: nitrogen(C/N) domestic wastewater. The control strategy aimed to adjust the flow rate of external carbon dosage to the anoxic zone, thus the concentration of nitrate plus nitrite(NOx--N) in the anoxic zone was kept closed to the set point. The relationship was studied between the NOx--N concentration in the anoxic zone(S_ NO) and the dosage of external carbon, and the results showed that the removal efficiency of the total nitrogen(TN) could not be largely improved by double dosage of carbon source when S_ NO reached about 2 mg/L. Through keeping S_ NO at the level of about 2 mg/L, the demand of effluent quality could be met and the carbon dosage could be optimized. Based on the Activated Sludge Model No.1(ASM No.1), a simplified mathematical model of external carbon dosage was developed. Simulation results showed that PI controller and feed-forward PI controller both had good dynamic response and steady precision. And feed-forward PI controller had better control effects due to its consideration of influent disturbances.

Nitrogen removal from municipal wastewater by limit-oxic/anoxic/oxic biological aerated filter system

In this study,a three-stage biological aerated filter(BAF) system was proposed for the enhancement of nitrogen removal in the treatment of low carbon-to-nitrogen ratio(C/N ratio) municipal wastewater.Operational parameters were studied for each process for maximum nitrite accumulation in the nitrification step and nitrite adaptation in the denitrification step.Nitrite accumulation during nitrification could be controlled by the dissolved oxygen(DO) concentration,presenting a mean value of 40% at around 1.0 mg DO/L.Denitrification could be adapted to nitrite and the process was stable if nitrite in the reactor was keep low.Once the operational parameters were established,the process was stable and a steady state was maintained for over 30 days,and the various indexes of discharged water were up to the Discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002) Level-one A.It was concluded that the three-stage BAF system proposed in this study was excellent in nitrogen removal performance by employing three-column functioning as short-cut nitrification,short-cut denitrification and secondary nitrification,respectively.

Versatile Surface Modification of Ceramsite Via Honeycomb Calcium-aluminum-silicate-hydrate and Its Functionalization by 3-thiocyanatopropyltriethoxysilane for Enhanced Cadmium(Ⅱ) Removal

A low-cost and efficient filter medium for Cd(Ⅱ) removal was prepared by anchoring-SCN functional groups(by 3-thiocyanatopropyltriethoxysilane, TCPS) on ceramsite via the approach of synthesizing a honeycomb calciumaluminum-silicate-hydrate(C-A-S-H) layer as intermediate. The specific surface area of ceramsite was increased enormously by more than 50 times because of the modification of honeycomb layer. Moreover, the abundant Si-OH bonds existing in the structure of CAS-H can serve as active sites for TCPS. The combined effects ensure that the hybrid filter medium(named ceramsite/C-A-S-H/TCPS) demonstrated a high Cd(Ⅱ) adsorption capacity of 18.27 mg·g^-1 for particle size of 0.1-0.6 mm, 12.63 mg·g^-1 for 0.6-1.25 mm and 8.64 mg·g^-1 for 1.25-2.35 mm. The Cd(Ⅱ) adsorption capacity per unit area of ceramsite/C-A-S-H/TCPS(0.1-0.6 mm) is up to 4.07 mg·m^-2, which is much higher than that of many nano-adsorbents. In addition, ceramsite/C-AS-H/TCPS could maintain a high removal efficiency(> 85%) in a wide range of p H 3-11 and showed excellent selectivity in the presence of competing ions. Furthermore, Cd(Ⅱ) could be desorbed from ceramsite/C-A-S-H/TCPS composites with nearly 100%, suggesting the potential application in recycling of heavy metal ions.

Fuzzy Control of Nitrate Recirculation and External Carbon Addition in A/O Nitrogen Removal Process

Nitrogen and phosphorous concentrations of effluent water must be taken into account for the design and operation of wastewater treatment plants. In addition, the requirement for effluent quality is becoming strict. Therefore, intelligent control approaches are recently required in removing biological nutrient. In this study, fuzzy control has been successfully applied to improve the nitrogen removal. Experimental results showed that a close relationship between nitrate concentration and oxidation-reduction potential (ORP) at the end of anoxic zone was found for anoxic/oxic (A/O) nitrogen removal process treating synthetic wastewater. ORP can be used as online fuzzy control parameter of nitrate recirculation and external carbon addition. The established fuzzy logic controller that includes two inputs and one output can maintain ORP value at - 86 mV and - 90 mV by adjusting the nitrate recirculation flow and external carbon dosage respectively to realize the optimal control of nitrogen removal, improving the effluent quality and reducing the operating cost.

Optimization of material removal strategy in milling of thin-walled parts

The optimal material removal strategy can improve a geometric accuracy and surface quality of thin-walled parts such as turbine blades and blisks in high-speed ball end milling.The dominant conception in the material removal represents the persistence of the workpiece cutting stiffness in operation to advance the machining accuracy and machining efficiency.On the basis of theoretical models of cutting stiffness and deformation,finite element method (FEM) is applied to calculate the virtual displacements of the thin-walled part under given virtual loads at the nodes of the discrete surface.With the reference of deformation distribution of the thin-walled part,the milling material removal strategy is optimized to make the best of bracing ability of still uncut material.This material removal method is summarized as the lower stiffness region removed firstly and the higher stiffness region removed next.Analytical and experimental results show the availability,which has been verified by the blade machining test in this work,for thin-walled parts to reduce cutting deformation and meliorate machining quality.