Massoud Pirbazari

Hybrid membrane filtration process for leachate treatment

Abstract A hybrid technology known as the ultrafiltration-biologically active carbon (UF-BAC) process that amalgamates adsorption, biodegradation and membrane filtration is found to be highly efficient for treatment of landfill leachates. The process employs bioactive powdered activated carbon (PAC) with a leachate-acclimated microbial culture for the simultaneous sorption and biodegradation of organic constituents. Tubular cross-flow ultrafiltration membrane modules separate out colloids and microorganisms, and a high quality permeate is obtained. Batch biokinetic studies were performed for the two leachates to evaluate their extent of biodegradability and biodegradation kinetics. The process efficiencies for both leachates were in the range of 95–98% in terms of TOC removal, and exceeded 97% for specific organic pollutants. The UF-BAC process compared well with the PACT process in terms of organic removal, and produced higher quality effluent in terms of suspended solids (100% removal). The study demonstrated that addition of 1% PAC mitigated permeate flux deterioration attributed to membrane fouling and concentration polarization, and enhanced permeate transport. Possible mechanisms for flux amelioration are discussed.

GAC adsorber design protocol for the removal of off-flavors

Abstract This paper investigates the effectiveness of granular activated carbon (GAC) for removing off-flavor compounds of water—geosmin and 2-methylisoborneol (MIB). More specifically, it focuses on the development of an appropriate modeling approach and experimental protocol for the design of fixed-bed GAC adsorbers. Adsorption equilibrium, rate and long-term mini-column studies were conducted on a bench-scale for geosmin and MIB to estimate the equilibrium and mass-transfer parameters required for adsorber modeling. The dispersed flow homogeneous surface diffusion model (DFHSDM) was used for the prediction/simulation of the adsorber dynamics. Scale-up procedures based on dimensional analysis and similitude were employed for the design of full-scale adsorbers from bench-scale adsorbers, and for performance forecasting of full-scale adsorbers under different operating conditions. More importantly, operation and maintenance (O & M) costs were estimated for full-scale adsorbers directed at the removal of off flavor compounds, based on carbon utilization rates and disposal costs. These estimates were obtained for different plant capacities and empty bed contact times (EBCTs).

Current Production by Bacterial Communities in Microbial Fuel Cells Enriched from Wastewater Sludge with Different Electron Donors

Electricity production by bacterial communities enriched from wastewater sludge with lactate, succinate, N-acetyl-D-glucosamine (NAG), acetate, formate, and uridine were monitored in dual-chamber microbial fuel cells (MFCs). Stable electricity production was observed after 300 h for communities enriched from lactate, acetate, and formate, while communities enriched with succinate, NAG, and uridine stabilized only after 700 h. The average peak current densities and maximum power densities generated from bacterial consortia were significantly higher than those generated from pure cultures of Shewanella oneidensis MR-1. Microbial assemblages were analyzed by DGGE, and planktonic and anode-attached bacterial communities varied as a function of electron donors: Firmicutes, β-Proteobacteria, and Bacteroidetes dominated the planktonic bacterial communities while anode-attached communities consisted mainly of δ-Proteobacteria, β-Proteobacteria, and Firmicutes. Similar bacterial populations were enriched in MFCs fed with lactate, NAG, and uridine and with succinate, acetate, and formate. Cross-feeding experiments with different fuels indicated that enriched microbial consortia were able to utilize a variety of fuel sources and displayed considerable stability, efficiency, and robustness of power generation in comparison to pure cultures. In addition, characterizations of cultivated Shewanella strains suggested that DGGE analysis likely missed active members of exoelectrogenic populations.

Bioadsorber efficiency, design, and performance forecasting for alachlor removal

This study discusses a mathematical modeling and design protocol for bioactive granular activated carbon (GAC) adsorbers employed for purification of drinking water contaminated by chlorinated pesticides, exemplified by alachlor. A thin biofilm model is discussed that incorporates the following phenomenological aspects: film transfer from the bulk fluid to the adsorbent particles, diffusion through the biofilm immobilized on adsorbent surface, adsorption of the contaminant into the adsorbent particle. The modeling approach involved independent laboratory-scale experiments to determine the model input parameters. These experiments included adsorption isotherm studies, adsorption rate studies, and biokinetic studies. Bioactive expanded-bed adsorber experiments were conducted to obtain realistic experimental data for determining the ability of the model for predicting adsorber dynamics under different operating conditions. The model equations were solved using a computationally efficient hybrid numerical technique combining orthogonal collocation and finite difference methods. The model provided accurate predictions of adsorber dynamics for bioactive and non-bioactive scenarios. Sensitivity analyses demonstrated the significance of various model parameters, and focussed on enhancement in certain key parameters to improve the overall process efficiency. Scale-up simulation studies for bioactive and non-bioactive adsorbers provided comparisons between their performances, and illustrated the advantages of bioregeneration for enhancing their effective service life spans. Isolation of microbial species revealed that fungal strains were more efficient than bacterial strains in metabolizing alachlor. Microbial degradation pathways for alachlor were proposed and confirmed by the detection of biotransformation metabolites and byproducts using gas chromatography/mass spectrometry.

Emissions of Volatile and Semi-Volatile Organic Compounds and Particulate Matter from Hot Asphalts

Asphalts are widely used in paving of roads, and water-proof sealing of building roofs, tanks and containers. This study evaluated the qualitative and quantitative characteristics of emissions from hot asphalts and bitumen that included reactive organic gases (ROGs) and particulate matter (PM). The ROGs consisted of several volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs) of environmental concern. The latter included several polynuclear aromatic hydrocarbons (PAHs) and alkanes. An experimental laboratory testing, sampling and analysis protocol was developed for obtaining efficient and cost-effective a priori estimates of asphalt emissions. The investigation identified and quantified the emissions of organics and evaluated the magnitudes as well as particle size distributions of PM emissions. The study demonstrated that the asphalt type and temperature greatly affected the emission characteristics, and that several organic compounds emitted were partitioned between gaseous and...

Evaluation of microbial fuel cell Shewanella biocathodes for treatment of chromate contamination

This paper presents data comparing Shewanella strains acting as biocatalysts under fumarate and chromate reducing conditions in a microbial fuel cell. Catalyzing fumarate reduction, Shewanella strains show a maximum power generation of between 10.2 and 59.4 nW cm−2. Comparisons between product formation and current transfer indicate either incomplete oxidation of fumarate or utilization of a separate source of electrons. Similar comparisons under chromate reducing conditions indicate initial utilization of the electrode as the sole electron source followed by a use of an unknown reducing electron pool. Additionally, we show that fuel cell systems, with Shewanella acting as the sole biocatalysts at the cathode, are capable of achieving reduction of chromium concentrations to less than 5 ppb, well within acceptable guidelines established by regulatory agencies.

Modeling of bioactive carbon adsorbers: a hybrid weighted residual-finite difference numerical technique

Phenomenological mathematical models incorporating adsorption, mass transfer, and biofilm degradation were developed for performance prediction/simulation of bioactive carbon fixed-bed and fluidized-bed adsorbers in wastewater treatment. The model equations were solved by a numerical technique combining a weighted residual technique such as orthogonal collocation with finite difference method. This hybrid technique was numerically consistent and stable and provided accurate solutions at computing times lower than those corresponding to pure orthogonal collocation. The bioadsorber model parameters were independently determined from carefully designed laboratory-scale experiments and correlations. The model predictions of bioadsorber effluent concentration profiles were in strong agreement with the experimental data, illustrating the good predictive capability of the model. Sensitivity studies were performed to identify the influence of model parameters on the bioactive adsorber dynamics.

Biological denitrification of reverse osmosis brine concentrates: II. Fluidized bed adsorber reactor studies

This phase of the study (Part II) investigates the application of a high-rate fluidized bed adsorber reactor (FBAR) process for biological denitrification of reverse osmosis (RO) brine concentrate....

Predictive Modeling for Bioactive Fluidized Bed and Stationary Bed Reactors: Application to Dairy Wastewater

Bioadsorber models were formulated, and a systematic protocol was developed for adsorber modeling and design. These models were used for forecasting the performance of bioactive and non bioactive reactors in two configurations: fluidized bed reactor (with effluent recycle), and stationary bed reactor. The models incorporated important phenomena associated with adsorption and biofilm degradation, and used total organic carbon (TOC) as a lumped parameter for measuring the wastewater strength. The protocol could be easily applied to bioactive reactors with non-adsorbing media such as sand, polymers and glass. The protocol included the development of experimental techniques for evaluating model parameters. Laboratory-scale adsorption equilibrium and rate studies were conducted to evaluate the equilibrium and mass-transfer parameters, respectively. Biokinetic experiments were performed to determine the biodegradation parameters including kinetic coefficients for biological growth and decay, and the yield coeff...

Pyrolytic destruction of polychlorinated biphenyls in a reductive atmosphere

Abstract This paper discusses the development of an innovative technology for the pyrolytic destruction of halogenated hydrocarbons in a reductive environment. The technology developed demonstrated the potential for resource recovery, as reaction products could be commercially used. The process was specifically directed at the dehalogenation of polychlorinated biphenyls (PCBs), a class of chlorinated compounds most difficult to thermally decompose due to the high strength of their carbon-chlorine bonds. PCBs have extensive industrial applications, and are regarded as pollutants of serious environmental concern due to their persistence and insidious health effects. Pyrolysis experiments were conducted under controlled laboratory conditions in batch reactor systems with Aroclor 1254 (a mixture of PCB congeners) to evaluate the process feasibility, and to determine the destruction and removal efficiencies (DREs). The pyrolysis was conducted under a variety of operating conditions to investigate the effect on DREs due to changes in process variables such as reactor residence time, reaction temperature, and reactant (methane) concentration. Under optimal conditions — a residence time of 7 minutes, reaction temperature of 1000°C, and stoichiometric excess methane — a DRE of over 99.999% was achieved. The reaction products were dehalogenated hydrocarbons, hydrogen chloride, and soot. The dehalogenated compounds formed were identified as aliphatic and aromatic hydrocarbons by gas chromatography/mass spectrometry (GC /MS). The study also included a scientific analysis of free-radical reactions and associated mechanisms involved in the decomposition of the halogenated hydrocarbons. Achievement of the highest DREs suggests that the process needs further investigation as a method for dehalogenation of chlorinated hydrocarbons with the potential of product recovery for commercial use.