A three-layer diffusion-cell to examine bio-enhanced dissolution of chloroethene dense non-aqueous phase liquid

Microbial reductive dechlorination of trichloroethene (TCE) and perchloroethene (PCE) in the vicinity of their dense non-aqueous phase liquid (DNAPL) has been shown to accelerate DNAPL dissolution. A three-layer diffusion-cell was developed to quantify this bio-enhanced dissolution and to measure the conditions near the DNAPL interface. The 12 cm long diffusion-cell setup consists of a 5.5 cm central porous layer (sand), a lower 3.5 cm DNAPL layer and a top 3 cm water layer. The water layer is frequently refreshed to remove chloroethenes at the upper boundary of the porous layer, while the DNAPL layer maintains the saturated chloroethene concentration at the lower boundary. Two abiotic and two biotic diffusion-cells with TCE DNAPL were tested. In the abiotic diffusion-cells, a linear steady state TCE concentration profile between the DNAPL and the water layer developed beyond 21 d. In the biotic diffusion-cells, TCE was completely converted into cis-dichloroethene (cis-DCE) at 2.5 cm distance of the DNAPL. Dechlorination was likely inhibited up to a distance of 1.5 cm from the DNAPL, as in this part the TCE concentration exceeded the culture’s maximum tolerable concentration (2.5 mM). The DNAPL dissolution fluxes were calculated from the TCE concentration gradient, measured at the interface of the DNAPL layer and the porous layer. Biotic fluxes were a factor 2.4 (standard deviation 0.2) larger than abiotic dissolution fluxes. This diffusion-cell setup can be used to study the factors affecting the bio-enhanced dissolution of DNAPL and to assess bioaugmentation, pH buffer addition and donor delivery strategies for source zones.     

Biodegradation and bio-sorption of antibiotics and non-steroidal anti-inflammatory drugs using immobilized cell process

In the present study, the removal mechanisms of four antibiotics (sulfamethoxazole, sulfadimethoxine, sulfamethazine, and trimethoprim) and four non-steroidal anti-inflammatory drugs (acetaminophen, ibuprofen, ketoprofen, and naproxen) in immobilized cell process were investigated using batch reactors. This work principally explores the individual or collective roles of biodegradation and bio-sorption as removal routes of the target pharmaceuticals and the results were validated by various experimental and analytical tools. Biodegradation and bio-sorption were found as dominant mechanisms for the drug removal, while volatilization and hydrolysis were negligible for all target pharmaceuticals. The target pharmaceuticals responded to the two observed removal mechanisms in different ways, typically: (1) strong biodegradability and bio-sorption by acetaminophen, (2) strong biodegradability and weak bio-sorption by sulfamethoxazole, sulfadimethoxine, ibuprofen and naproxen, (3) low biodegradability and weak bio-sorption by sulfamethazine and ketoprofen, and (4) low biodegradability and medium bio-sorption by trimethoprim. In the sorption/desorption experiment, acetaminophen, sulfamethoxazole and sulfadimethoxine were characterized by strong sorption and weak desorption. A phenomenon of moderate sorption and well desorption was observed for sulfamethazine, trimethoprim and naproxen. Both ibuprofen and ketoprofen were weakly sorbed and strongly desorbed.     

Determination of 2,4- and 2,6-dinitrotoluene biodegradation limits

This study was carried out to explore the lowest achievable dinitrotoluene (DNT) isomer concentrations that would support sustained growth of DNT degrading microorganisms under an aerobic condition. Studies were conducted using suspended (chemostat) and attached growth (column) systems. The biodegradation limits for 2,4-dinitrotoluene chemostat and column system were 0.054 ± 0.005 and 0.057 ± 0.008 μM, respectively, and for 2,6-dinitrotoluene, the limits for chemostat and column system were 0.039 ± 0.005 and 0.026 ± 0.013 μM, respectively. The biodegradation limits determined in this study are much lower than the regulatory requirements, inferring that bacterial ability to metabolize DNT does not preclude applications of bioremediation (including natural attenuation) for DNT contaminated media.     

Use of fugacity model to analyze temperature-dependent removal of micro-contaminants in sewage treatment plants

Effluents from sewage treatment plants (STPs) are known to contain residual micro-contaminants including endocrine disrupting chemicals (EDCs) despite the utilization of various removal processes. Temperature alters the efficacy of removal processes; however, experimental measurements of EDC removal at various temperatures are limited. Extrapolation of EDC behavior over a wide temperature range is possible using available physicochemical property data followed by the correction of temperature dependency. A level II fugacity-based STP model was employed by inputting parameters obtained from the literature and estimated by the US EPA’s Estimations Programs Interface (EPI) including EPI’s BIOWIN for temperature-dependent biodegradation half-lives. EDC removals in a three-stage activated sludge system were modeled under various temperatures and hydraulic retention times (HRTs) for representative compounds of various properties. Sensitivity analysis indicates that temperature plays a significant role in the model outcomes. Increasing temperature considerably enhances the removal of β-estradiol, ethinyestradiol, bisphenol, phenol, and tetrachloroethylene, but not testosterone with the highest biodegradation rate. The shortcomings of BIOWIN were mitigated by the correction of highly temperature-dependent biodegradation rates using the Arrhenius equation. The model predicts well the effects of operating temperature and HRTs on the removal via volatilization, adsorption, and biodegradation. The model also reveals that an impractically long HRT is needed to achieve a high EDC removal. The STP model along with temperature corrections is able to provide some useful insight into the different patterns of STP performance, and useful operational considerations relevant to EDC removal at winter low temperatures.     

Biodegradation of aromatic hydrocarbons by Haloarchaea and their use for the reduction of the chemical oxygen demand of hypersaline petroleum produced water

Ten halophilic Archaea (Haloarchaea) strains able to degrade aromatic compounds were isolated from five hypersaline locations; salt marshes in the Uyuni salt flats in Bolivia, crystallizer ponds in Chile and Cabo Rojo (Puerto Rico), and sabkhas (salt flats) in the Persian Gulf (Saudi Arabia) and the Dead Sea (Israel and Jordan). Phylogenetic identification of the isolates was determined by 16S rRNA gene sequence analysis. The isolated Haloarchaea strains were able to grow on a mixture of benzoic acid, p-hydroxybenzoic acid, and salicylic acid (1.5 mM each) and a mixture of the polycyclic aromatic hydrocarbons, naphthalene, anthracene, phenanthrene, pyrene and benzo[a]anthracene (0.3 mM each). Evaluation of the extent of degradation of the mixed aromatic hydrocarbons demonstrated that the isolates could degrade these compounds in hypersaline media containing 20% NaCl. The strains were shown to reduce the COD of hypersaline crude oil reservoir produced waters significantly beyond that achieved using standard hydrogen peroxide treatment alone.     

Effects of solids retention time on the performance of bioreactors bioaugmented with a 17β-estradiol-utilizing bacterium, Sphingomonas strain KC8

This study investigated the performance of lab-scale sequencing batch reactors (SBRs) that were inoculated with nitrifying activated sludge and bioaugmented with a Sphingomonas strain KC8 (a 17β-estradiol-degrading bacterium). The bioaugmented SBRs were supplied with synthetic wastewater (average initial total organic carbon (TOC) = 175 mg L⁻¹ and average initial ammonia-N = 25 mg L⁻¹) and daily dose of 17β-estradiol (1 mg L⁻¹) and operated under three solid retention times (SRTs) of 5, 10, and 20 d. After three times periods of the operating SRTs, the overall removal of TOC (>87%) and ammonia (>91%) was similar in all the SBRs. Higher 17β-estradiol removals (>99%) were observed for the SBRs. Neither estrogens nor estrogenic activity was detected in the treated water, except some samples from the SBR operating under 5 d of SRT. The ratios of known estrogen degraders (Sphingomonas strain KC8 and ammonia-oxidizing bacteria) and amoA gene to the total bacterial population decreased as SRT increased, suggesting the presence of unknown estrogen-degraders in SBRs operating at SRT = 10 and 20 d. Real-time-terminal-restriction fragment length polymorphism analysis showed that the evenness of microbial community structures was not affected by the SRT; while, the diversity indices suggest that longer SRTs might lead to more diverse microbial community structure. Overall, the results suggested that bioaugmented bioreactors operating at long SRTs (10 and 20 d) were effective in removing 17β-estradiol to the non-estrogenic treatment endpoint.     

Biodegradation of chlorpyrifos by either single or combined cultures of some soilborne plant pathogenic fungi

Abstract

Biodegradation of chlorpyrifos was studied in liquid culture media amended with either single or combined eight different plant pathogenic fungi isolated from the continuous cropping wheat fields. The average recovery of chlorpyrifos from the liquid media was found to be 86.1%. The detection limit of chlorpyrifos by the analytical method used was 19 ppb. Data showed that the growth of mixed fungi at concentrations up to 200 ppm of chlorpyrifos was higher than in the control treatment. Chlorpyrifos concentrations declined in the medium of combined fungi more than it did in the medium of any single fungus with increase in the incubation period. The amount of chlorpyrifos recovered was 79.8 ppm (39.9%) in the combined fungal cultures after 21 days. However, those recovered from the media of Fusarium graminearum, F. oxysporum, Rhizoctonia solani, Cladosporhim cladosporiodes, Cephalosporium sp., Trichoderma viridi, Alternaria alternata, and Cladorrhinum brunnescens, ranged from 48.0 to 74.8%. The half‐life value (T_1/2) for chlorpynfos was 15.8 day in the medium amended with mixed fungi. However, for the single cultures it ranged from 19.3 to 33.0 day.     

Microbial degradation of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in compost

The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) [P(3HB)] or copolymers with 10% [P(3HB-co-10%3HV)] and 20% [P(3HB-co-20%3HV)] 3-hydroxyvaleric acid was studied in small household compost heaps. Degradation was measured through loss of weight (surface erosion) and changes in molecular weight and mechanical strength. It was concluded, on the basis of weight loss and loss of mechanical properties, that P(3HB) and P(3HB-co-3HV) plastics were degraded in compost by the action of microorganisms. No decrease inM _w could be detected during the degradation process. The P(3HB-co-20%3HV) copolymer was degraded much faster than the homopolymer and P(3HB-co-10%3HV). One hundred nine microbial strains capable of degrading the polymersin vitro were isolated from the samples used in the biodegradation studies, as well as from two other composts, and identified. They consisted of 61 Gram-negative bacteria (e.g.,Acidovorax facilis), 10 Gram-positive bacteria (mainlyBacillus megaterium), 35Streptomyces strains, and 3 molds.     

Anaerobic Biodegradation of Blends Based on Polyvinyl Alcohol

The presented work deals with blends composed of polyvinyl alcohol (PVA) and biopolymers (protein hydrolysate, starch, lignin). PVA does not belong to biologically inert plastics but its degradation rate (particularly under anaerobic conditions) is low. A potential solution to the issue problem lies in preparation of blends with readily degradable substrates. We studied degradation of blow-molded films made of commercial PVA and mentioned biopolymers in an aqueous anaerobic environment employing inoculation with digested activated sludge from the municipal wastewater treatment plant. Films prepared in the first experimental series were to be used for comparing biodegradation of blends modified with native or plasticized starch; in this case effect of plasticization was not proved. The degree of PVA degradation after modification with native or plasticized starch increases in a striking and practically same manner already at a starch level as low as approximately 5 wt.%. Films of the second experimental series were prepared as additionally modified with protein hydrolysate and lignin. Only lignin-modified samples exhibited a somewhat lower degree of biodegradation but regarding the measure of lignin present in blend this circumstance is not essential. Level of biodegradation with all discussed films differed only slightly—within range of experimental error.     

Biodegradation of Polycaprolactone Powders Proposed as Reference Test Materials for International Standard of Biodegradation Evaluation Method

Polycaprolactone (PCL) powders were prepared from PCL pellets using a rotation mechanical mixer. PCL powders were separated by sieves with 60 and 120 meshes into four classes; 0–125 μm, 125–250 μm, 0–250 μm and 250–500 μm. Biodegradation tests of PCL powders and cellulose powders in an aqueous solution at 25°C were performed using the coulometer according to ISO 14851. Biodegradation tests of PCL powders and cellulose powders in controlled compost at 58°C were performed by the Mitsui Chemical Analysis and Consulting Service, Inc. according to ISO 14855-1 and by using the Microbial Oxidative Degradation Analyzer (MODA) instrument according to ISO/DIS 14855-2. PCL powders were faster biodegraded than cellulose powders. The reproducibility of biodegradation of PCL powders is excellent. Differences in the biodegradation of PCL powders with different class were not observed by the ISO 14851 and ISO/DIS 14855-2. An enzymatic degradation test of PCL powders with different class was studied using an enzyme of Amano Lipase PS. PCL with smaller particle size was faster degraded by the enzyme. PCL powders with regulated sizes from 125 μm to 250 μm are proposed as a reference material for the biodegradation test.