Environmental Technology

The large-scale integration of intermittent distributed energy resources has led to increased uncertainty in the planning and operation of distribution networks. The optimal flexibility dispatch is a recently introduced, power flow-based method that a distribution system operator can use to effectively determine the amount of flexibility it needs to procure from the controllable resources available on the demand side. However, the drawback of this method is that the optimal flexibility dispatch is inexact due to the relaxation error inherent in the second-order cone formulation. In this paper we propose a novel bi-level optimization problem, where the upper level problem seeks to minimize the relaxation error and the lower level solves the earlier introduced convex second-order cone optimal flexibility dispatch (SOC-OFD) problem. To make the problem tractable, we introduce an innovative reformulation to recast the bi-level problem as a non-linear, single level optimization problem which results in no loss of accuracy. We subsequently investigate the sensitivity of the optimal flexibility schedules and the locational flexibility prices with respect to uncertainty in load forecast and flexibility ranges of the demand response providers which are input parameters to the problem. The sensitivity analysis is performed based on the perturbed Karush-Kuhn-Tucker (KKT) conditions. We investigate the feasibility and scalability of the proposed method in three case studies of standardized 9-bus, 30-bus, and 300-bus test systems. Simulation results in terms of local flexibility prices are interpreted in economic terms and show the effectiveness of the proposed approach.

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Porous electrodes are important in many physical-chemical processes including capacitive deionization (CDI), a desalination technology where ions are adsorbed from solution into the electrostatic double layers (EDLs) formed at the electrode-solution interface inside two juxtaposed porous electrodes. A key property of the porous electrode is the charge efficiency of the EDL, Λ,

Referaat Wageningen UR Glastuinbouw heeft met financiering van Productschap Tuinbouw de historie en achtergronden van electrochemisch geactiveerd water beschreven en mogelijkheden verkend voor toepassingen binnen de agrarische sector. In Nederland is alleen het gebruik van geactiveerd water als biocide sinds 2009 toegestaan. Geactiveerd water bestaat onder meer uit chloorgas, onderchlorig zuur en hypochloriet. Mede door een hoog oxidatie-reductiepotentiaal (ORP 750-1100

The effectiveness of the advanced oxidation process (UV/H 2 O 2) in decolorizing real textile wastewater polluted with commercial reactive dyes-Reactive Yellow 84 and Reactive Red 141was investigated. All the experiments were performed in a lab-scale reactor with the original high pH of the wastewater. The dyeing wastewater was decolorized in 5 hours. After its acidification to pH 3 the decolorization process was more efficient. Full decolorization was then achieved in 2 hours and the decrease in COD exceeded 70%. The reaction rate constants obtained were as follows: at pH 11.4, 0.0065 min-1 ; at pH 7, 0.0044 min-1 , and at pH 3, 0.019 min-1 , which testified to pH importance for UV/H 2 O 2 oxidation process.

Anaerobic methanethiol (MT) degradation by mesophilic (308C) alkaliphilic (pH 10) communities was studied in a lab-scale Upflow Anaerobic Sludge Bed (UASB) reactor inoculated with a mixture of sediments from the Wadden Sea (The Netherlands), Soap Lake (Central Washington), and Russian soda lakes. MT degradation started after 32 days of incubation. During the first 252 days, complete degradation was achieved till a volumetric loading rate of 7.5 mmol MT/L/day, and sulfide, methane, and carbon dioxide were the main reaction products. Temporary inhibition of MT degradation occurred after MT peak loads and in the presence of dimethyl disulfide (DMDS), which is the autooxidation product of MT. From day 252 onwards, methanol was dosed to the reactor as co-substrate at a loading rate of 3-6 mmol/L/day to stimulate growth of methylotrophic methanogens. Methanol was completely degraded and also a complete MT degradation was achieved till a volumetric loading rate of 13 mmol MT/L/day (0.77 mmol MT/gVSS/day). However, from day 354 till the end of the experimental run (day 365), acetate was formed and MT was not completely degraded anymore, indicating that methanol-degrading homoacetogenic bacteria had partially outcompeted the methanogenic MTdegrading archea. The archeal community in the reactor sludge was analyzed by DGGE and sequencing of 16S rRNA genes. The methanogenic archea responsible for the degradation of MT in the reactor were related to Methanolobus oregonensis. A pure culture, named strain SODA, was obtained by serial dilutions in medium containing both trimethyl amine and dimethyl sulfide (DMS). Strain SODA degraded MT, DMS, trimethyl amine, and methanol. Flow sheet simulations revealed that for sufficient MT removal from liquefied petroleum gas, the extraction and biological degradation process should be operated above pH 9.

Purpose With the predicted climate change, it is expected that the chances of river flooding increase. During flood events, sediments will resuspend and when sediments are polluted, contaminants can be transferred to the surrounding water. In this paper we discuss a numerical intraparticle diffusion model that simulates desorption of dieldrin from a suspension of contaminated porous sediment particles with a well-characterized particle size distribution. The objective of this study was to understand the desorption rate (flux) of dieldrin from a suspension of field-aged sediment at different hydraulic retention times (HRT) of the aqueous phase and to elaborate the effect of particle-size distribution on mass transfer. Materials and methods Desorption kinetics of dieldrin, a persistent organic pollutant (POP), were experimentally measured and described in a separate paper using fieldcontaminated sediment. A radial diffusion model, accommodating intraparticle reversible sorption kinetics, aqueous phase pore diffusion, and a sink term for bulk aqueous phase refreshment was used to describe the experimental data. Results and discussion We observed rapid equilibrium of contaminants between small particles (10 μm) and the surrounding water even though the sorption affinity of dieldrin towards organic matter was high. On the contrary, for the larger particles (84 μm), calculations show that desorption was limited by intraparticle diffusion. Combining small and larger particles in our radial diffusion model resulted in the biphasic desorption behavior often observed even when using a linear isotherm. Conclusions Flood events will result in an increase of desorption rate of POPs from sediments to the surrounding water. HRT and the particle-size distribution determine the desorption rate. We conclude that nonstationary diffusion within organic matter is the main process of mass transfer. Particle size distributions are very valuable to understand the phenomenology related to mass transfer limitations often described as limited bioavailability and can be used as basis to develop engineering options to limit contaminant mass fluxes into the environment.

fore, milling had no effect on desorption behavior of contaminants, as the diffusion length will not be affected. In our opinion, both the particle size and spatial configuration of organic matter are rate determining parameters of the desorption process. Conclusions. Flood events will result in an increase of desorption rate of POPs from sediments to the surrounding water. HRT and particle size determine the concentration gradient and, thereby, the desorption rate. Furthermore, the diffusion length will be smaller when sediment particles are suspended and more water is present to decrease the aqueous concentration. We conclude that non-stationary diffusion within organic matter is the main process of mass transfer. The combination of simulated in-situ measurements of desorption from sediments with generic measurable parameters like flow rate and particle size distribution results in a quantitative measurable flux of contaminants, which resembles the in-situ (bio)availability as the result of dynamic processes in the sediment/water system. Recommendations and Perspectives. The results obtained provided a sound basis for mechanistic modeling of POP mass transfer from sediment to water. The modeling results will be presented in a separate paper. Besides the HRT, also mixing conditions can be changed to assess the desorption from sediment layers. The possibility to combine flow rate and mixing intensity enables the study of the effect of hydraulically different river systems on desorption of contaminants. In a long term perspective we foresee a link with hydrology and sediment transport with desorption in water bodies.

This research aimed at studying the oxidation process, to verify the effectiveness of coliform inactivation and to evaluate the formation of ozonation disinfection byproducts (DBP) in anoxic sanitary wastewater treated with ozone/hydrogen peroxide applied at doses of 2.6 mg O 3 L-1 and 2.0 mg H 2 O 2 L-1 with contact time of 10 min and 8.1 mg O 3 L-1 and 8.0 mg H 2 O 2 L-1 with contact time of 20 min. The mean chemical oxygen demand (COD) reductions were 7.50 and 9.40% for applied dosages of 2.5-2.8 and 6.4-9.4 mg O 3 L-1 + 2.0 and 8.0 mg H 2 O 2 .L-1 , respectively. The Escherichia coli (E. coli) inactivation range was 2.98-4.04 log 10 and the total coliform inactivation range was 2.77-4.01 log 10. The aldehydes investigated were formaldehyde, acetaldehyde, glyoxal and methylglyoxal. It was observed only the formation of acetaldehyde that ranged 5.53 to 29.68 µg L-1 .

The reuse of polymer flooding produced water (PFPW) generated in oil and gas industry is limited by its salt content, making desalination by electrodialysis a promising treatment option. Therefore, this study aimed to 1) assess the technical feasibility of employing electrodialysis to desalinate PFPW generated in assorted scenarios, and 2) evaluate the reuse of the electrodialysis-desalted water to confect polymer-flooding solution. The experimental work involved desalting two kinds of synthetic PFPW solutions, one with relatively low salinity (TDS = 5000 mg/L, brackish PFPW), and another with high salinity (TDS = 32,000 mg/L, sea PFPW), at two different temperatures, and later reusing the desalted solution to prepare viscous solutions. For the electrodialysis runs, the effects of feed composition and temperature on water transport, energy consumption and current efficiency were analyzed. It was found that the presence of polymer did not significantly influence the water transport rate or the specific energy consumption for the seawater cases, but had a measurable effect when desalting brackish water at 20°C. It was also found that some polymer remained in the stack, the loss occurring faster for the brackish PFPW. Still, both kinds of reused PFPW probed adequate to be employed as a basis for preparing n polymer solution.

This study presents fluidized bed electrodes as a new device for disinfection. In the fluidized bed electrodes system, granular activated carbon particles were suspended, and an alternating radio frequency electric field was applied over the suspended bed. Proof-of-principle studies with the luminescent non-pathogenic bacterium Escherichia coli YMc10 demonstrated that disinfection with fluidized bed electrodes requires both the presence of granular activated carbon particles and the application of radio frequency electric field. Disinfection was investigated at various frequencies in range from 80 to 200 kHz at electric field strength of 6 ± 0.5 V/cm during 6 h. The largest decrease of E. coli viable cell concentration in the liquid (from 10 8 to 10 6 CFU/mL) was obtained at an optimum frequency of 140 kHz. Possible mechanisms of this electromediated disinfection are discussed in the manuscript. The results are promising for development of a new disinfection process with fluidized bed electrodes.

Household digesters are anaerobic reactors applied mostly in rural areas of developing countries with tropical climate. The Chinese dome digester is the most popular household digester type in Asia and Africa, and has become the basis for contemporary developments in the household digester sector around the world. Household digesters are operated at ambient temperatures and have no internal mixing device, making them simple to operate. In the absence of internal mixing mechanism, the Chinese dome digester is mixed via pressure variation during gas production, gas use and feeding. Since mixing is limited in household digesters, they are operated at low organic loading rates and long hydraulic retention time when compared with forced mixed reactors. This review analyses and presents the various types of domestic biogas plants and operating parameters, with emphasis on mixing. Experimental results of household reactors, forced mixed reactors with different mixing modes and intensities were also reviewed and compared.

Household or domestic biogas plants constitute a growing sub-sector of the anaerobic digestion industry worldwide, but had received low research attention for improvements. The Chinese dome digester (CDD), a major type of domestic biogas plant, is a naturally mixed, unheated and low tech system that is mainly used in rural areas. In this study, a multiphase computational fluid dynamics (CFD) model was applied to evaluate and subsequently improve mixing in a lab scale Chinese dome digester. The normal Chinese dome digester (CDD1) and two baffle configurations were investigated to improve the hydraulic mixing in the digester (CDD2 and CDD3 respectively) . 2D time dependent numerical simulations were done with the three-phase, phase field model in COMSOL Multiphysics in a CDD geometry. Residence time distribution (RTD) curves were derived for all the configurations to evaluate and compare performances. In addition, three hydraulic indicators were also studied to evaluate mixing improve...

An algorithm for calculating the scattering factors of atomic fragments in molecules as defined by the Stockholder recipe is presented. This method allows the calculation, from ab initio molecular wave functions, of structure factors including individual anisotropic atomic temperature factors. These structure factors agree with the model used in most leastsquares multipole-refinement procedures. Calculations on the H20 molecule illustrate the method.