Mixed- and plug-flow performances of an anaerobic biofilter treating 2-ethylhexanoic acid

The performance of a 20-L anaerobic biofilter treating 2-ethyl-hexanoic acid (2-EHA) operating with the effluent recirculated was compared with that of the same biofilter operated without any recirculation. The recirculation of effluent was at a rate of 60 L/h through the biofilter. Tracer experiments were carried out to study the hydrodynamics in the biofilter under different modes of operation. The dispersion number (D/UL) obtained from these tracer experiments for the biofilter operated with and without effluent recirculation were 0.65 and 0.06, respectively. These values show that the recirculation was effective in achieving a mixed-flow pattern in the biofilter, whereas the biofilter operated without recirculation was essentially a plug-flow column with a moderate level of axial dispersion. The feed consisted of 2-EHA at a concentration of 8200 mg/L, which is equivalent to a COD of 20,000 mg/L. The optimal performance of the mixed-flow biofilter was at a hydraulic retention time (HRT) of 1.1 d, with a COD removal efficiency of 92.8% and a biogas production rate of 6.44 L/L biofilter vol/d. The biofilter failed at 0.83 d HRT, as a result of washout of biomass at this high hydraulic loading rate. By comparison, the optimal performance achieved for the plug-flow system was at 2 d HRT. The COD removal efficiency was 74.1%, and biogas production rate was 2.13 L/L biofilter vol/d. When the HRT was lowered to 1.5 d, failure occurred owing to inhibition as indicated by the low methane yield of 0.192 L/g COD removed. The superior performance of the mixed-flow mode can be attributed to the presence of the recycle stream, which diluted and evenly distributed the feed.     

Combining mixing regimes for optimized anaerobic wastewater treatment

Operational practice of high-rate anaerobic bioreactors such as upflow anaerobic sludge bed (UASB) reactors is generally based on maximization of the biomass concentration and, in the case of more than one reactor compartment, operation in parallel. In this article, a modeling approach is used to postulate that the treatment performance of anaerobic bioreactors can be improved by simple operational measures. To achieve minimized effluent soluble substrate concentrations, operation of two reactors in series combined with active exchange of biomass between both reactors is suggested. In this way, substrate concentrations lower than the minimum achievable concentration in a completely mixed reactor can be achieved. It is furthermore suggested that maximized biomass concentrations (and solid retention times [SRTs]) do not necessarily lead to minimized effluent concentrations of organic material. At elevated SRTs, the soluble microbial products resulting from biomass turnover are shown to represent the main fraction of soluble organic material in the effluent of the reactor, limiting treatment efficiency.     

Electrochemical technologies for treating petroleum industry wastewater

This review focuses on recent developments in electrochemical technology (with special emphasis on electrocoagulation, electro-oxidation, and electro-Fenton) to treat petroleum industry effluents (offshore and hydraulic fracturing extraction, as well as refinery effluents). In addition, an overview is given of what these processes face to position themselves as consolidated technologies.     

Pretreatment of swine wastewater using anaerobic filter

Efforts were made to assess the efficiency of an anaerobic filter packed with porous floating ceramic media and to identify the optimum operational condition of anaerobic filter as a pretreatment of swine wastewater for the subsequent biological removal of nitrogen and phosphorus. A stepwise decrease in hydraulic retention time (HRT) and an increase in organic loading rate (OLR) were utilized in an anaerobic filter reactor at mesophilic temperature (35°C). The optimum operating condition of the anaerobic filter was found to be at an HRT of 1 d. A soluble chemical oxygen demand (COD) removal efficiency of 62% and a total suspended solids removal efficiency of 39% at an HRT of 1 d were achieved with an OLR of 16.0 kg total COD/(m³·d), respectively. The maximum methane production rate approached 1.70 vol of biogas produced per volume of reactor per day at an HRT of 1 d. It was likely that the effluent COD/total Kjeldahl nitrogen ratio, of 22, the COD/total phosphorous ratio of 47, and the high effluent alkalinity >2500 mg/L as CaCO₃ of the anaerobic filter operated at an HRT of 1 d was adequate for the subsequent biological removal of nitrogen and phosphorus.     

厌氧悬浮填料生物膜反应器处理费托合成废水

采用厌氧悬浮填料生物膜反应器工艺对费托合成废水进行处理,考察了高有机负荷条件下系统的运行情况.有机负荷小于31.1g/(L·d)时,COD去除率达97%以上;当有机负荷从39.7g/(L·d)增加至56.3g/(L·d)时,厌氧反应对COD的去除率从88%降至6l%.实验结果表明,填料生物膜比悬浮污泥具有更高的活性,M...     

Whole cell immobilised biosensors for toxicity assessment of a wastewater treatment plant treating phenolics-containing waste

Wastewater treatment plants dealing with industrial wastes are often susceptible to overload of toxic influent that can partially or completely destroy treatment for extended periods. An obvious candidate for monitoring toxicity in such wastewater systems is bioluminescent bacteria. However, the natural bioluminescent bacteria can be particularly sensitive to some industrial wastes and therefore their response to normal operational conditions does not reflect the status of the microbial community responsible for treatment. Moreover, the salt dependence of the marine bioluminescent bacteria, and the temperature sensitivity of some strains, further complicate their use. Here we describe the construction of whole cell genetically modified bioluminescent biosensors and their immobilisation for use in monitoring the toxicity of a complex industrial wastewater containing phenolic materials. A hand-held luminometer was designed for laboratory or field use, and the immobilisation system designed with several things in mind: the geometry of the instrument; the need for containment of GM bacteria; the maximisation of the bioavailability of the wastewater to the biosensor. The performance of a candidate GM sensor was compared with Vibrio fischeri in liquid culture and after immobilisation in thin films of poly(vinyl alcohol) (PVA) cryogels. The biosensors were tested against pure phenol and 3-chlorophenol as a reference toxic chemical known to be much more toxic to bacteria than phenol. The biosensors were then tested with the phenolics-containing industrial wastewater. The immobilisation system proved to operate predictably with pure toxicants, and was able to discriminate toxicity of various zones within the wastewater treatment plant.     

A novel process for anaerobic composting of municipal solid waste

A novel process has been developed and evaluated in a pilotscale program for conversion of the biodegradable fraction of municipal solid waste (MSW) to methane via anaerobic composting. The sequential batch anaerobic composting (SEBAC) process employs leachate management to provide organisms, moisture, and nutrients required for rapid conversion of MSW and removal of inhibitory fermentation products during start-up. The biodegradable organic materials are converted to methane and carbon dioxide in 21–42 d, rather than the years required in landfills.     

Development of a novel,two-step process for treating municipal biosolids for beneficial reuse

Modern municipal sewage waste treatment plants use conventional mechanical and biological processes to reclaim wastewaters. This process has an overall effect of converting a water pollution problem into a solid waste disposal problem (sludges or biosolids). An estimated 10 million tons of biosolids, which require final disposal, are produced annually in the United States. Although numerous disposal options for biosolids are available, including land application, landfilling, and incineration, disposal costs have risen, partly because of increased federal and local environmental restrictions(1). A novel, thermomechanical biosolids pre-treatment process, which allows for a variety of potential value-added uses, was developed. This two-step process first employs thermal explosive decompression to inactivate or kill the microbial cells and viruses. This primary step also results in the rupture of a small amount of the microbial biomass and increases the intrinsic fluidity of the biosolids. The second step uses shear to effect a near-complete rupturing of the microbial biomass, and shears the nondigested organics, which increases the overall surface area. Pretreated biosolids may be subjected to a secondary anaerobic digestion process to produce additional fuel gas, and to provide for a high-quality, easily dewatered compost product. This novel biosolids pretreatment process was recently allowed a United States patent.     

Biodegradation of toluene in a membrane biofilter

A membrane biofilter is used to biodegrade toluene in the gas phase. Active microorganisms are immobilized on the outside of a hollow fiber membrane cartridge and air containing toluene as the contaminant is passed through the membrane fibers. A porous polysulfone membrane containing water in the pore is used through which both toluene and oxygen are diffused to the biofilm attached to the outside surface. High conversion of toluene (84%) is achieved with a 16 second gas-phase residence time, based on total internal volume of the hollow fibers. A mathematical model is then developed to estimate toluene removal efficiencies at higher air flow rates.     

Graphdiyne as a novel nonactive anode for wastewater treatment: A theoretical study

Electrochemical oxidation of water to produce highly reactive hydroxyl radicals (OH) is the dominant factor that accounts for the organic compounds removal efficiency in water treatment. As an emerging carbon-based material, the investigation of electrocatalytic of water to produce OH on Graphdiyne (GDY) anode is firstly evaluated by using first-principles calculations. The theoretical calculation results demonstrated that the GDY anode owns a large oxygen evolution reaction (OER) overpotential (η^OER = 1.95 V) and a weak sorptive ability towards oxygen evolution intermediates (HO*, not OH). The high Gibbs energy change of HO* (3.18 eV) on GDY anode makes the selective production of OH (ΔG = 2.4 eV) thermodynamically favorable. The investigation comprises the understanding of the relationship between OER to electrochemical advanced oxidation process (EAOP), and give a proof-of-concept of finding the novel and robust environmental EAOP anode at quantum chemistry level.     

Preparation of carbon fibers/carbon/alumina tubular composite membranes and their applications in treating Cu-CMP wastewater by a novel electrochemical process

In this study, the alumina substrate was first prepared by the extrusion method, then followed by poly-vinylydenchloride (PVDC) film wrapping, PVDC carbonization, catalyst precursor coating, and the chemical vapor deposition (CVD) process to grow carbon fibers on the carbon interlayer. The carbon fibers/carbon/alumina tubular composite membranes (CCA-TCMs) thus obtained, with a pore size distribution ranging from 2 to 10 nm, were further characterized by scanning electron microscopy, transmission electron microscopy, and permporometry. A prepared CCA-TCM of this kind was incorporated into a novel simultaneous crossflow electrocoagulation and electrofiltration (EC/EF) treatment module to evaluate its capability in treating Cu-CMP (chemical mechanical polishing) wastewater. Crossflow EC/EF performance tests were carried out based on the 2³⁻¹ fractional factorial design using the electric field strength, crossflow velocity, and transmembrane pressure (TMP) as the experimental factors. Under the optimal operating conditions, the CCA-TCM associated EC/EF treatment module is capable of treating Cu-CMP wastewater in a proper manner. Permeate thus obtained had a turbidity of below 1 NTU and the removal efficiencies of total solids content, total organic carbon, copper, and silicon for Cu-CMP wastewater were 72%, 81%, 92%, and 87%, respectively.     

Operation of industrial-scale electron beam wastewater treatment plant

Textile dyeing processes consume large amount of water, steam and discharge filthy and colored wastewater. A pilot scale e-beam plant with an electron accelerator of 1 MeV, 40 kW had constructed at Daegu Dyeing Industrial Complex (DDIC) in 1997 for treating 1,000 m³ per day. Continuous operation of this plant showed the preliminary e-beam treatment reduced bio-treatment time and resulted in more significant decreasing TOC, COD_Cr, and BOD₅. Convinced of the economics and efficiency of the process, a commercial plant with 1 MeV, 400 kW electron accelerator has constructed in 2005. This plant improves the removal efficiency of wastewater with decreasing the retention time in bio-treatment at around 1 kGy. This plant is located on the area of existing wastewater treatment facility in DDIC and the treatment capacity is 10,000 m³ of wastewater per day. The total construction cost for this plant was USD 4 M and the operation cost has been obtained was not more than USD 1 M per year and about USD 0.3 per each m³ of wastewater.     

Dissolved air flotation for treating wastewater of the nuclear industry: preliminary results

Preliminary testing of dissolved air flotation (DAF) for wastewater treatment is presented. A combined coagulation-flocculation/DAF column system is used to remove oil and ⁶⁰Co from nuclear industry wastewater. In this work, operational conditions and coagulant/flocculant concentrations are optimized by varying pH. Determinations of air-solids ratio (G/S), retention time (θ), pressure (P), volume of depressurized air–water mixture (V), turbidity and ⁶⁰Co concentrations are reported. The effect of the treatment on the efficiency of separation of oily residues is also discussed. The results establish that the coagulant/flocculant system, formed by a modified polyamine (25 mgL^?1) and a slightly cationic polyacrylamide (1.5 mgL^?1), under specific operational conditions (pH = 7, mixing intensity Im₁ = 300 s^?1 and Im₂ = 30 s^?1), allowed the destabilization of colloidal matter, resulting in resistant flocs. It was concluded that by using G/S = 0.3, θ = 15 min, P = 620 kPa and V = 0.0012 m³, the greatest percentage removals of oil, turbidity, total cobalt and ⁶⁰Co were obtained. These preliminary results then show that dissolved air flotation represents a good alternative for treatment of nuclear industry wastewater contaminated with radionuclides.     

Synthesis and performances for treating oily wastewater of polyether copolymers based on polyethyleneimine

The demulsification of the oily wastewater generated in the oil recovery process is very important in the crude oil exploitation. In present work, 10 block copolymers based on polyethyleneimine were synthesized, and their performances for treating oily wastewater were studied. The evaluation of demulsification efficiency, the effects of temperature, and the dosage on the treatment of oily wastewater by prepared copolymers were also investigated. To explore the causes of the differences, the interface activity of prepared copolymer molecules at water‐oil interface was investigated by the interfacial tension, and a mechanism diagram of demulsification of wastewater by the prepared copolymers was proposed. The demulsification of wastewater could be divided into 3 processes that were (1) adsorption, (2) congestion, and (3) coalescence. The prepared copolymer molecule acted as a hand in the oily wastewater to achieve the demulsification.     

Mechanism and controlling strategy of the production and accumulation of propionic acid for anaerobic wastewater treatment

The production and accumulation of propionic acid affect significantly anaerobic wastewater treatment system, but the reasons are not approached until now. Based on the results of continuous-flow tests and the analysis of biochemistry and ecology, two mechanisms of producing propionic acid have been put forward. It is demonstrated that the reasons of propionic acid production and accumulation are not caused by higher hydrogen partial pressure. The combination of specific pH value and ORP is the ecological factor affecting propionic acid production, and the equilibrium regulation of NADH/NAD+ ratio in cells is the physiological factor. Meanwhile, it is put forward that using the two-phase anaerobic treatment process and the ethanol type fermentation in anaerobic reactor to avoid propionic acid accumulation are efficient methods.     

6-氨基青霉烷酸生产废水厌氧和深度处理实验研究

针对6-氨基青霉烷酸生产废水高污染物浓度,高硫酸根,难降解物质多的特点对废水经过硫酸根预处理,稀释3倍和6倍后,废水对厌氧污泥没有急毒性,厌氧污泥可以逐步适应废水环境。经过厌氧处理以及后续的Fenton深度处理,高浓度的6-氨基青霉烷酸生产废水COD_cr可由45450 mg/L 降到255 mg/L。出水COD_cr可达到污水三级排放标准。     

The anaerobic treatment of soft drink wastewater in UASB and hybrid reactors

The anaerobic treatment of soft drink wastewater (SDW) was studied in two laboratory reactors—a 1.8-L UASB reactor and a 3-L hybrid reactor-sludge bed containing a layer of polyurethane in the upper part, at 35°C. The highest organic loading rates (OLR) achieved were 13 and 16.5 g COD/L · D for hybrid and UASB reactors, respectively, with the treatment efficiency of about 80% for both reactors. Despite the higher treatment productivity achieved for the UASB reactor, its lower ability to generate a sufficient level of alkalinity led to difficulties in maintaining a stable operation performance. Therefore, the hybrid reactor seems to be indicated for OLR higher than 10 g COD/L · d and HRT lower than 1 D, from the point of view of reliability of these two systems. Both reactors can treat the SDW with pH influent up to 11.0. The feeding of reactors with higher pH influent values led to their quick failure because of alkali shock. The duration of the recovery period after alkali shock was about 1.5-2 mo.     

Polymer modified biomass of baker's yeast for treating simulated wastewater containing nickel and lead

Baker's yeast was cross‐linked by glutaraldehyde and then modified by grafting with poly(amic acid), which was prepared via reaction of pyromellitic dianhydride (PMDA) and arginine at 50°C. The morphology of the pristine, cross‐linked, and modified biomass was observed by microscope. The presence of poly(amic acid) on the biomass surface was verified by X‐ray photoelectron spectroscopy (XPS) analyses. Due to the high density of the functional groups on the modified biomass surface, the metal adsorption capacity for nickel and lead increased significantly, especially when the carboxylic acid groups were converted into carboxylate ions using NaOH. The adsorption process for nickel and lead adsorption followed the pseudo‐second‐order kinetics. The metal adsorption data were fitted with the Langmuir and Freundlich isotherms with the former having a better fit. Using the Langmuir adsorption isotherm, the maximum uptakes for nickel and lead were found to be 0.848 and 0.980 mmol g^?1 respectively which were about 15 and 11 times higher than the prisitine biomass. In the simulated wastewater containing 0.400 mmol l^?1 of Ni²⁺ and Pb²⁺, the metal adsorption capacity of Ni²⁺ and Pb²⁺ reached 0.365 mmol l^?1 and 0.390 mmol l^?1, respectively. The metal ions loaded biomass was regenerated using Ethylene Diamine Tetraacetic Acid (EDTA) solution and used repeatedly over four cycles with little loss of uptake capacity. Copyright © 2007 John Wiley & Sons, Ltd.     

Biofiltration of 1,1,1-trichloroethane by a trickle-bed air biofilter

The performance of a trickle-bed air biofilter (TBAB) in the removal of 1,1,1-trichloroethane (TCLE) was evaluated in concentrations varying from 0.025 to 0.049 g/m³ and at empty-bed residence time (EBRT) varying from 20 to 90 s. Nearly complete TCLE removal could be achieved for influent carbon loading between 0.98 and 5.88 g/m³ h. The TBAB appeared efficient for controlling TCLE emission under low-carbon-loading conditions. Carbon recoveries higher than 95% were achieved, demonstrating the accuracy of results. The carbon mass rate of the liquid effluent was approximately two orders of magnitude less than that of the effluent CO₂, indicating that dissolved TCLE and its derivatives in leachate were present in negligible amounts in the TBAB.     

Demonstration-scale evaluation of a novel high-solids anaerobic digestion process for converting organic wastes to fuel gas and compost

Early evaluations of the bioconversion potential for combined wastes such as tuna sludge and sorted municipal solid waste (MSW) were conducted at laboratory scale and compared conventional low-solids, stirred-tank anaerobic systems with the novel, high-solids anaerobic digester (HSAD) design. Enhanced feedstock conversion rates and yields were determined for the HSAD system. In addition, the HSAD system demonstrated superior resiliency to process failure. Utilizing relatively dry feedstocks, the HSAD system is approximately one-tenth the size of conventional low-solids systems. In addition, the HSAD system is capable of organic loading rates (OLRs) on the order of 20-25 g volatile solids per liter digester volume per d (gVS/L/d), roughly 4-5 times those of conventional systems

Current efforts involve developing a demonstration-scale (pilot-scale) HSAD system. A two-ton/d plant has been constructed in Stanton, CA and is currently in the commissioning/startup phase. The purposes of the project are to verify laboratory- and intermediate-scale process performance; test the performance of large-scale prototype mechanical systems; demonstrate the long-term reliability of the process; and generate the process and economic data required for the design, financing, and construction of full-scale commercial systems. This study presents conformational fermentation data obtained at intermediate-scale and a snapshot of the pilot-scale project