Impact of Dewatering on the Spatio-Temporal Distribution of Benthic Macroinvertebrate Communities in the Okpara River, Benin

Surface watercourses are areas of very high ecological and heritage value. Macroinvertebrates are bioindicators of the health of aquatic ecosystems. The aim of this study was to assess the effects of dewatering and re-watering cycles on benthic macroinvertebrate (BMI) communities. Two data collections were carried out at two stations (Okpara 1 and Okpara 2) on the Okpara river before and after dewatering. Thus, 8 samples of benthic macroinvertebrates and 12 physico-chemical parameters (T°C, pH, Transparency, Depth, Conductivity, Dissolved Oxygen that were measured in situ, and BOD5, COD, NH4+, NO3-, NO2- and PO43-) were assayed in the laboratory. Canonical Correspondence Analysis (CCA) was used to match physico-chemical data to MIB families. Shannon and Piélou diversity indices were used to determine the effects of dewatering on MIBs. The increase in temperature values of pH, BOD5, COD, NH4+, NO3-, NO2- and PO43-, after re-watering indicates the effect of dewatering on the quality of Okpara aquatic ecosystems. The benthic macrofauna collected consisted of 62.42% insects, 0.65% crustaceans, 6.48% molluscs, 0.72% worms and 0.14% arachnids. Whereas after re-watering, 21.67% insects, 0% crustaceans, 0.22% molluscs, 7.56% worms and 0.29% arachnids were recorded. Insects, crustaceans and molluscs were more abundant before dewatering than after. This was revealed by low abundances and taxonomic richness, as well as low Shannon index values of samples collected after re-watering.

An Energy-Efficient Routing Algorithm for UAV Formation Based on Time-Aggregated Graph

The limited energy and high mobility of unmanned aerial vehicles(UAVs)lead to drastic topology changes in UAV formation.The existing routing protocols necessitate a large number of messages for route discovery and maintenance,greatly increasing network delay and control overhead.A energyefficient routing method based on the discrete timeaggregated graph(TAG)theory is proposed since UAV formation is a defined time-varying network.The network is characterized using the TAG,which utilizes the prior knowledge in UAV formation.An energyefficient routing algorithm is designed based on TAG,considering the link delay,relative mobility,and residual energy of UAVs.The routing path is determined with global network information before requesting communication.Simulation results demonstrate that the routing method can improve the end-to-end delay,packet delivery ratio,routing control overhead,and residual energy.Consequently,introducing timevarying graphs to design routing algorithms is more effective for UAV formation.

A Discrete Multi-Objective Squirrel Search Algorithm for Energy-Efficient Distributed Heterogeneous Permutation Flowshop with Variable Processing Speed

In the manufacturing industry,reasonable scheduling can greatly improve production efficiency,while excessive resource consumption highlights the growing significance of energy conservation in production.This paper studies the problem of energy-efficient distributed heterogeneous permutation flowshop problem with variable processing speed(DHPFSP-VPS),considering both the minimum makespan and total energy consumption(TEC)as objectives.A discrete multi-objective squirrel search algorithm(DMSSA)is proposed to solve the DHPFSPVPS.DMSSA makes four improvements based on the squirrel search algorithm.Firstly,in terms of the population initialization strategy,four hybrid initialization methods targeting different objectives are proposed to enhance the quality of initial solutions.Secondly,enhancements are made to the population hierarchy system and position updating methods of the squirrel search algorithm,making it more suitable for discrete scheduling problems.Additionally,regarding the search strategy,six local searches are designed based on problem characteristics to enhance search capability.Moreover,a dynamic predator strategy based on Q-learning is devised to effectively balance DMSSA’s capability for global exploration and local exploitation.Finally,two speed control energy-efficient strategies are designed to reduce TEC.Extensive comparative experiments are conducted in this paper to validate the effectiveness of the proposed strategies.The results of comparing DMSSA with other algorithms demonstrate its superior performance and its potential for efficient solving of the DHPFSP-VPS problem.

Increasing realism in modelling energy losses in railway vehicles and their impact to energy-efficient train control

The reduction of energy consumption is an increasingly important topic of the railway system.Energy-efficient train control(EETC)is one solution,which refers to mathematically computing when to accelerate,which cruising speed to hold,how long one should coast over a suitable space,and when to brake.Most approaches in literature and industry greatly simplify a lot of nonlinear effects,such that they ignore mostly the losses due to energy conversion in traction components and auxiliaries.To fill this research gap,a series of increasingly detailed nonlinear losses is described and modelled.We categorize an increasing detail in this representation as four levels.We study the impact of those levels of detail on the energy optimal speed trajectory.To do this,a standard approach based on dynamic programming is used,given constraints on total travel time.This evaluation of multiple test cases highlights the influence of the dynamic losses and the power consumption of auxiliary components on railway trajectories,also compared to multiple benchmarks.The results show how the losses can make up 50%of the total energy consumption for an exemplary trip.Ignoring them would though result in consistent but limited errors in the optimal trajectory.Overall,more complex trajectories can result in less energy consumption when including the complexity of nonlinear losses than when a simpler model is considered.Those effects are stronger when the trajectory includes many acceleration and braking phases.

Experimental Research on the Dewatering of Dredged Sediment from Dianchi Lake

[Objective] The technological parameter suitable for the dewatering of dredged sediment from Dianchi Lake was studied.[Method] By means of the treatment method of sewage sludge in sewage treatment plant,flocculants including FeCl3,Al2(SO4)3 and PAM were taken as dewatering agents which were added in dredged sediment.[Result] The results showed that Al2(SO4)3 had better dewatering effect than FeCl3 and PAM,and the optimum dosing quantity of Al2(SO4)3 in dredged sediment was 170 mg/L,in addition,the water quality of supernatant met the first class B standard of GB18918-2002 and could be directly discharged to nature water without pollution.[Conclusion] The study could provide a simple and feasible way for the rapid dewatering of dredged sediment from Dianchi Lake,which would be convenient for the disposal and resource utilization of dredged sediment.

Nitrogen removal from sludge dewatering effluent through anaerobic ammonia oxidation process

Anaerobic ammonia oxidation（Anammox） process is a novel and promising wastewater nitrogen removal process. The feasibility of transition of Anammox from denitrification and the performance of lab-scale Anammox biofilm reactor were investigated with sludge dewatering effluent. The results showed that Anammox process could be successfully started up after cultivation of denitrification biofilm and using it as inoculum. The transition of Anammox from denitrification was accomplished within 85 d. Anammox process was found suitable to remove ammonia from sludge dewatering effluent. The effluent ammonia concentration was detected to be 23.11 mgN/L at HRT of 28 h when influent ammonia concentration was fed 245 mgN/L, which was less than that for the national discharge standard Ⅱ （25 rngN/L） of China. Volumetric total nitrogen loading rate was up to 584.99 mg TN/（L. d） at HRT of 17 h, while influent concentrations were kept 243.25 mg NH4＊ -N/L and 288.31 mg NO2^- -N/L.

Study on Deep Well Dewatering Optimization Design in Deep Foundation Pit and Engineering Application

Based on analyses of the theories of groundwater unsteady flow in deep well dewatering in the deep foundation pit, Theis equations are chosen to calculate and analyze the relationship between water level drawdown of confined aquifer and dewatering duration. In order to reduce engineering cost and diminish detrimental effect on ambient surrounding, optimization design target function based on the control of confined water drawdown and four restriction requisitions based on the control of safe water level, resistance to throwing up from the bottom of foundation pit, avoiding excessively great subsidence and unequal surface subsidence are proposed. A deep well dewatering project in the deep foundation pit is optimally designed. The calculated results including confined water level drawdown and surface subsidence are in close agreement with the measured results, and the optimization design can effectively control both surface subsidence outside foundation pit and unequal subsidence as a result of dewatering.

Optimization of dewatering schemes for a deep foundation pit near the Yangtze River, China

A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River. Among the strata, there are two confined aquifers, between which lies an aquiclude that is partially missing. To guarantee the safety of pit excavation, the piezometric head of the upper confined aquifer, where the pit bottom is located, should be 1 m below the pit bottom, while that of the lower confined aquifer should be dewatered down to a safe water level to avoid uplift problem. The Yangtze River levee is notably close to the pit, and its deformation caused by dewatering should be controlled. A pumping test was performed to obtain the hydraulic conductivity of the upper confined aquifer. The average value of the hydraulic conductivity obtained from analytical calculation is 20.45 m/d, which is larger than the values from numerical simulation（horizontal hydraulic conductivity K_H = 16 m/d and vertical hydraulic conductivity K_V = S m/d）. The difference between K_H and K_V indicates the anisotropy of the aquifer. Two dewatering schemes were designed for the construction and simulated by the numerical models for comparison purposes. The results show that though the first scheme could meet the dewatering requirements, the largest accumulated settlement and differential settlement would be94.64 mm and 3.3‰, respectively, greatly exceeding the limited values. Meanwhile, the second scheme,in which the bottoms of the waterproof curtains in ramp B and the river side of ramp A are installed at a deeper elevation of-28 m above sea level, and 27 recharge wells are set along the levee, can control the deformation of the levee significantly.

Pretreatment of Crude Oil by Ultrasonic-electric United Desalting and Dewatering

A technology of ultrasonic-electric united desalting and dewatering of crude oil is studied. The ultrasonic setup is designed to form a standing-wave field, which is more efficient for agglomeration of water particles. The desalting and dewatering results of the ultrasonic-electric united process are compared with those of the electric process. For high salt-contenting crude oil （40-70 mg·L ^-1）, the salt content is still above 10.0 mg·L^-1 after crude oil has been treated by two-stage electric desalting process in refinery, which cannot meet the need of refinery. Ultrasonic-electric united process is a novel technology for treating the high salt-contenting oil. On the optimal operating conditions of the ultrasonic-electric united process, the salt content of crude oil can be reduced from 67 5 mg·L^-1 to 3.97 mg·L ^-1 by one-stage ultrasonic-electric united process, and the water content falls below 0.3% （by volume）. The results show that the ultrasonic-electric united process is more effective than the electric process in high salt-contenting oil desalting. This technology should be useful in the refinery process.

Comparative filtration and dewatering behavior of vitrinite and inertinite of bituminous coal:Experiment and simulation study

The filtration and dewatering of fine clean coal not only ensure industrial water recycle in coal washing plant,but also reduce the moisture of coal product in order to meet the requirements of combustion or coking industry.Fine clean coal is mainly composed by organic matter,and the property difference of different organic matter determines the filtration and dewatering behavior.In this investigation,vitrinite and inertinite were separated from a clean bituminous coal,and the comparative filtration and dewatering behavior of vitrinite and inertinite were conducted.The results showed that inertinite has lower dewatering rate and higher filter cake moisture than vitrinite.The analysis of filter cake structure showed that inertinite particle is easier to be broken into small particles due to the difference of mechanical properties,thus forming more compact filter cake than vitrinite.The analysis of particle surface properties showed that vitrinite is more hydrophobic than inertinite,which makes water easier drained from filter cake.The simulation study showed that the structure of inertinite is more porous than that of vitrinite,and the interaction between inertinite and water is stronger than that between vitrinite and water.This study provides a theoretical basis for improving coal dewatering by selectively improving coal maceral hydrophobicity.

Reconstructed rheometer for direct monitoring of dewatering performance and torque in tailings thickening process

To further clarify the dewatering performance and torque evolution during the tailings thickening process,a self-made rake was connected to a rheometer to monitor the shear stress and torque.The dewatering performance of the total tailings was greatly improved to a solid mass fraction of 75.33%in 240 min.The dewatering process could be divided into three stages:the rapid torque growth period,damping torque growth period,and constant torque thickening zone.The machine restart was found to have a significant effect on the rake torque;it could result in rake blockage.Furthermore,the simultaneous evolution of the torque and solid mass fraction of thickened tailings was analyzed.A relationship between the torque and the solid mass fraction was established,which followed a power function.Both the experimental and theoretical results provide a reference for the deep cone thickener design and operation to enhance the dewatering performance.

Calculation of groundwater head distribution with a close barrier during excavation dewatering in confined aquifer

When pumping is conducted in confined aquifer inside excavation pit(waterproof curtain),the direction of the groundwater seepage outside the excavation changes from horizontal to vertical owing to the existence of the curtain barrier.There is no analytical calculation method for the groundwater head distribution induced by dewatering inside excavation.This paper first analyses the mechanism of the blocking effects from a close barrier in confined aquifer.Then,a simple equation based on analytical solution is proposed to calculate groundwater heads inside and outside of the excavation pit with waterproof curtain(hereafter refer to close barrier)in a confined aquifer.The distribution of groundwater head is derived according to two conditions:(i)pumping with a constant water head,and(ii)pumping with a constant flow rate.The proposed calculation equation is verified by both numerical simulation and experimental results.The comparisons demonstrate that the proposed model can be applied in engineering practice of excavation.

Influence of Filter Cloth on the Cathode on the Electroosmotic Dewatering of Activated Sludge

The mechanical dewatering of activated sludge is troublesome due to its high compressibility of solids. The dewatering can be enhanced dramatically by the use of electroosmosis,in which an electric field is applied to the sludge cake.In this study,the influence of filter cloth on the cathode on the dewatering of activated sludge was investigated.It was found that thicker filter cloth led to lower water removal from the sludge cake,so a stainless steel cathode net with small pore size instead of filter cloth was applied,which improves the dewatering efficiency and reduces the electric power consumption.Moreover,water absorbent materials were helpful to remove the water from the sludge cake.For the electroosmotic dewatering at 7 kPa and 24 V·cm-1,the water content in the sludge cake decreased to 60%(by mass) with the average 0.075 kW·h·kg-1of water removed by using the cathode net.

Effect of a starch-based filter aid on the dewatering of fine clean coal

The dewatering of fine, flotation cleaned coals from Huaibei and Xuzhou (bituminous) and Yongcheng (anthracite) were studied. The supernatant and filter cake were examined to determine the rate and extent of flocculation and dewatering. A starch-based filter aid was used to increase flocculation and dewatering rates. The filtration constant, K, and compression index, s, of the Yongcheng slurry were measured under various conditions. A designed experiment was performed to determine optimum conditions for dewatering. The results showed that the filter aid enhanced flocculation and coagulation of the fine cleaned coal slurry, enhanced the structure of the filter cake and promoted dewatering of the cake. Moisture content in the cake was reduced to 17% after vacuum filtration.

Application of Screw Press Filter for Oily Sludge Dewatering

In order to find suitable oily sludge treatment equipment for a produced water treatment station of an oilfield in Iraq,the widely used mechanical dewatering equipments overseas including plate and frame filter,belt press filter,centrifugal filter and screw press filter were compared and analyzed,and the application situation of screw press filter was investigated at site. The site survey showed that,screw press filter was an integrated equipment combined with functions of concentrating and dewatering,which was characterized by low water content of filter cake,small occupied area,easy to separate,no blocking and can realize self-cleaning,which is suitable to low concentration sludge. Screw press filter can simplify oily sludge treatment process,and save engineering construction and operation cost,which is a better choice for oily sludge dewatering. The design of screw press filter adopted in the produced water treatment station of an oilfield in Iraq was introduced here.

Solidification Efficiency and Mechanism of Conventional Curing Agents for Sewage Sludge Stabilization and Dewatering

One of the challenges faced by sewage sludge treatment and disposal is its higher water content,and how to efficient dewater those hazardous materials properly is welcome in practice. This study stabilized the sewage sludge via the using of conventional curing agents and calcined aluminum salts,and the corresponding dewatering mechanisms and structural changes of the stabilized sludge were further comparable analyzed.Experimental results showed that wollastonite and kaolin exhibit a relative higher dewatering efficiency as compared to other conventional curing agents; however the releasing rate of heavy metals of Cu,Cr,Ni for kaolin solidification and Zn,Pb for wollastonite solidification is higher than the sludge samples solidified by other curing agents. For comparison,the sludge samples solidified by calcined aluminum salts (AS),calcium ash,Mg-based curing agent,tricalcium aluminate( C_3A) show a lower heavy metals leaching potential and unconfined compressive strength. In addition,the economic characteristics and local availability of AS,calcium ash,C_3A and CaO makes it have a broad prospect in extension and application. These findings are of great significance for stabilization and dewatering of sewage sludge.

Numerical simulation and land subsidence control for deep foundation pit dewatering of Longyang Road Station on Shanghai Metro Line 18

In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled.

Mathematical Model for Electroosmotic Dewatering of Activated Sludge

The mechanical dewatering of activated sludge is difficult due to its high compressibility, which can be improved by electroosmosis. In electroosmosis, direct electric field is applied to sludge cake. Based on the conductivity modes of different sludge beds, a model is presented in which sludge cake consists of two series parts in the circuit: a dewatered bed and an undewatered one. The dewatered bed called solid conductor is mainly made up of immovable water and sludge particles. The undewatered bed includes movable water and solid conductor, which are connected in parallel in the circuit. The model describes the variation of water content with time and electric power consumption as a function of water content in sludge cake, and interprets the reason for the variation of electroosmotic dewatering rate. Comparison with the experimental data for electroosmotic dewatering under constant voltage supports the validity of the model.

A Hybrid Model for Reliability Aware and Energy-Efficiency in Multicore Systems

Recently,Multicore systems use Dynamic Voltage/Frequency Scaling(DV/FS)technology to allow the cores to operate with various voltage and/or frequencies than other cores to save power and enhance the performance.In this paper,an effective and reliable hybridmodel to reduce the energy and makespan in multicore systems is proposed.The proposed hybrid model enhances and integrates the greedy approach with dynamic programming to achieve optimal Voltage/Frequency(Vmin/F)levels.Then,the allocation process is applied based on the availableworkloads.The hybrid model consists of three stages.The first stage gets the optimum safe voltage while the second stage sets the level of energy efficiency,and finally,the third is the allocation stage.Experimental results on various benchmarks show that the proposed model can generate optimal solutions to save energy while minimizing the makespan penalty.Comparisons with other competitive algorithms show that the proposed model provides on average 48%improvements in energy-saving and achieves an 18%reduction in computation time while ensuring a high degree of system reliability.

Characterisation of pore fluid salinity dependent evaporative dewatering of kaolin using dielectric spectroscopy

Realising the importance of pore fluid salinity on the dewatering behaviour of fine-grained porous systems,the present study systematically investigated such impacts on temporal moisture dynamics of kaolin subjected to evaporative dewatering.A detailed discussion is provided pertaining to the background processes dictating evaporative dewatering response and corresponding alterations in the dielectric behaviour of kaolin.Frequency dependent dielectric spectra of soil,which can be considered as the fingerprint of the transient changes in the condition of water phase within the pore system of the soil and associated densification,are monitored in real time during dewatering using an open-ended coaxial probe with a vector network analyser.The spatial sensitivity of the coaxial probe has been quantified through layered media approach.Combining the results of volume change behaviour of the material along with its moisture loss response,the study characterised the hydro-mechanical response of the material from the windows of frequency dependent dielectric spectroscopy.