Use of a Sequencing Batch Reactor for Nitrogen and Phosphorus Removal from Municipal Wastewater

In this study, a suspended growth sequencing batch reactor (SBR) and an attached cum suspended growth SBR were used to investigate the performance characteristics of nitrogen and phosphorus (NP) removal from municipal sewage. The effects of three controlling factors, namely batch loading rate, feed pattern (initial feed or step feed), and mixing/aeration ratio, on NP removal were investigated under nine different experimental conditions. Owing to a large number of possible combinations among the controlling factors and different experimental conditions, it is very difficult to enumerate all the available combinations experimentally. In view of this, the Taguchi method, a cost-effective technique for design of experiments, was exploited for estimating the optimal operating condition. This study also evaluated the difference between the suspended growth SBR and the attached cum suspended growth SBR. The total nitrogen (TN), total phosphorus (TP), total biochemical oxygen demand (TBOD)5, and suspended solids (SS) removal efficiencies were 90.2, 83.9, 98.6, and 93.0%, respectively, for the suspended growth SBR. The corresponding values for the attached cum suspended growth SBR were 92.6, 82.1, 98.3, and 93.1%, respectively. It was observed that the batch loading rate influenced the efficiencies in terms of TN removal. It was also noted that step feed and mixing/aeration ratio had significant impact on TP removal performance. The optimal operating condition for the suspended growth SBR system in terms of batch loading rate, feed pattern, and mixing/aeration ratio were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 1-to-1, respectively. The associated TN, TP, TBOD5, and SS removal efficiencies for the suspended growth SBR were 93.8, 98.2, 99.6, and 98.5%, respectively. The corresponding results for the attached cum suspended growth SBR system were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 3-to-1, respectively. Similarly, the corresponding removal efficiencies for the attached cum suspended growth SBR were 94.7, 97.8, 99.3, and 98.8%, respectively.     

Utilization of an Activated Sludge for the Improvement of an Existing Thermophilic Wastewater Treatment System

A pilot-scale activated sludge system was started to determine its effectiveness in treating the thermophilic biological effluent from an existing organic chemical industrial wastewater treatment system. Preliminary results demonstrated that an additional 95% biological oxygen demand and 65% dissolved organic carbon removal was achieved. In addition, significant biodegradation of the volatile organic compounds and organic nitrogen was observed.     

Removal of Methyl Isobutyl Ketone From Contaminated Air by Trickle-Bed Air Biofilter

A laboratory-scale trickle-bed air biofilter was evaluated for the removal of methyl isobutyl ketone (MIBK) from a waste gas stream. Six-millimeter (6?mm) Celite pellets (R-635) were used as the biological attachment medium. Effects of MIBK volumetric loading rates on removal efficiency, biofilter reacclimation, biomass growth, and removal kinetics were studied under three different operating conditions, namely, backwashing and two intermittent periods (off chemical—no MIBK input; and off flow-no flow input). Backwashing of the biofilter once a week with full-medium fluidization removed the excess biomass and attained stable long-term performance with over 99% removal efficiency for loading rates less than 3.26?kg chemical oxygen demand (COD)/m3?day. The two intermittent periods could also sustain high removal efficiency for loading rates up to 1.09?kg?COD/m3?day without any backwashing. The recovery time increased with an increase in loading rates. Furthermore, the intermittent operations required a longer time to recover than backwashing. The pseudo-first-order removal rate constant decreased with an increase in volumetric loading rate. The removal kinetics showed an apparent dependency on the experimental operating conditions.     

Treatment of High-Strength Pharmaceutical Wastewater and Removal of Antibiotics in Anaerobic and Aerobic Biological Treatment Processes

Anaerobic and aerobic treatment of high-strength pharmaceutical wastewater was evaluated in this study. A batch test was performed to study the biodegradability of the wastewater, and the result indicated that a combination anaerobic-aerobic treatment system was effective in removing organic matter from the high-strength pharmaceutical wastewater. Based on the batch test, a pilot-scale system composed of an anaerobic baffled reactor followed by a biofilm airlift suspension reactor was designed. At a stable operational period, effluent chemical oxygen demand (COD) from the anaerobic baffled reactor ranged from 1,432 to 2,397?mg/L at a hydraulic retention time (HRT) of 1.25 day, and 979 to 1,749?mg/L at an HRT of 2.5 day, respectively, when influent COD ranged from 9,736 to 19,862?mg/L. As a result, effluent COD of the biofilm airlift suspension reactor varied between 256 and 355?mg/L at HRTs of from 5.0 to 12.5 h. The antibiotics ampicillin and aureomycin, with influent concentrations of 3.2 and 1.0?mg/L, respectively, could be partially degraded in the anaerobic baffled reactor: ampicillin and aureomycin removal efficiencies were 16.4 and 25.9% with an HRT of 1.25 day, and 42.1 and 31.3% with HRT of 2.5 day, respectively. Although effective in COD removal, the biofilm airlift suspension reactor did not display significant antibiotic removal, and the removal efficiencies of the two antibiotics were less than 10%.     

Biodegradation of Nitroaromatics and RDX by Isolated Rhodococcus Opacus

Identification of bacteria that can utilize a wide range of nitroaromatic compounds will allow development of more effective biological treatment methods in industrial wastewater treatment processes and environmental remediation efforts. A new strain of Rhodococcus opacus capable of mineralizing or transforming nitroaromatic and nitramine compounds of importance was isolated. Specifically, the bacterium were found to utilize 2,4,6-trinitrophenol (TNP) as a sole carbon and nitrogen source and have a yield coefficient of 0.16 g cells-N/g TNP-N. The Edwards model was found to provide the best fit to the data and the estimated inhibited growth parameters μmax, KS, and KI were 0.58?h?1, 25, and 112?mg/L, respectively. It was found that the TNP-degraders could degrade 2,4-dinitrophenol as the sole carbon and nitrogen source and utilize 1,3,5-trinitrobenzene as the sole nitrogen source. Additionally, the results show that the isolates are able to cometabolize 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 4-nitrophenol (4-NP), and 2,4- and 2,6-dinitrotoluene (2,4 and 2,6-DNT) to some extent when TNP is also present.     

Biodegradation Kinetics of MTBE in Laboratory Batch and Continuous Flow Reactors

Methyl tert-butyl ether (MTBE) biodegradation was investigated using a continuously stirred tank reactor with biomass retention (porous pot reactor) operated under aerobic conditions. MTBE was fed to the reactor at an influent concentration of 150 mg/L (1.70 mM). An identical reactor was operated as a killed control under the same conditions. Operation of these reactors demonstrated that removal of MTBE was biological and suggests that biomass retention is critical for effective degradation. MTBE removal exceeded 99.99% when the volatile suspended solids concentration in the reactor was above 600 mg/L. Batch experiments conducted using mixed liquor from the porous pot reactor indicated that the individual rates of biodegradation of MTBE and tert-butyl alcohol (TBA) increase with increasing initial concentration. When batch tests were later repeated, the MTBE degradation rates were found to have increased while the TBA degradation rates remained constant. All batch tests confirmed that the degradation rate of TBA governed the overall degradation rate (degradation rate of both MTBE and TBA). The presence of TBA at lower concentrations did not affect the rate of MTBE degradation; however, higher concentrations of TBA did reduce the rate of MTBE biodegradation.     

Combined System for Biological Removal of Nitrogen and Carbon from a Fish Cannery Wastewater

A combined system composed of three sequentially arranged reactors, anaerobic-anoxic-aerobic reactors, was used to treat the wastewater generated in the tuna cookers of a fish canning factory. These wastewaters are characterized by high chemical oxygen demand (COD) and nitrogen concentrations. The anaerobic process was performed in an upflow anaerobic sludge blanket reactor operated in two steps. During Step I different influent COD concentrations were applied and organic loading rates (OLRs) up to 4 g COD/(L?d) were achieved. During Step II hydraulic retention time (HRT) was varied from 0.5 to 0.8 days while COD concentration in the influent was constant at 6 g COD/L. The OLRs treated were up to 15 g COD/(L?d). When HRTs longer than 0.8 days were used, COD removal percentages of 60% were obtained and these values decreased to 40% for a HRT of 0.5 days. The denitrification process carried out in an upflow anoxic filter was clearly influenced by the amount of carbon source supplied. When available carbon was present, the necessary COD/N ratio for complete denitrification was around 4 and denitrification percentages of 80% were obtained. The nitrification process was successful and was almost unaffected by the presence of organic carbon (0.2–0.8 g TOC/L), with ammonia removal percentages of 100%. Three recycling ratios (R/F) between the denitrification and nitrification reactors were applied at 1, 2, and 2.5. The overall balance of the combined system indicated that COD and N removal percentages of 90% and up to 60%, respectively, were achieved when the R/F ratio was between 2 and 2.5.     

Experimental Validation of the Static Granular Bed Reactor for Industrial Waste Anaerobic Treatment

The static granular bed reactor (SGBR) is a unique high-rate anaerobic reactor designed to operate in a simple downflow manner, offering high chemical oxygen demand (COD) removal efficiencies (greater than 90%) resulting from high biomass retention in the system. A study was performed to evaluate the SGBR versus a control system, the upflow anaerobic sludge blanket (UASB) reactor, and to evaluate performance idiosyncrasies of the SGBR and the control. The two reactors were operated at three different hydraulic retention times (HRTs): 8, 16, and 24 h. The reactors treated synthetic wastewater, intended to simulate food industry waste, composed of sucrose and nonfat dry milk. Overall, COD removal was higher for the SGBR than for the UASB reactor. In particular, at a HRT of 8 h, the SGBR achieved a COD removal of 90.7% and the UASB reactor reduced the COD concentration by 77.5%. The UASB reactor’s specific COD loading factor proved rate limiting with values ranging from 0.19 to 0.94?gCOD/(gVS?d) versus 0.11 to 0.34?gCOD/(gVS?d) for the SGBR. A tracer study idealized hydraulics within the two systems, and the results showed minimal dead volume and 4–6% short circuiting for both reactors.     

Comparison of Liquid and Gas-Phase Photooxidation of MTBE: Synthetic and Field Samples

The feasibility of photooxidation treatment of methyl tert-butyl ether (MTBE) in water was investigated using two systems: (1) a slurry falling film photoreactor and (2) an integrated air stripping with gas phase photooxidation system. Methyl tert-butyl ether-contaminated synthetic water and field samples from contaminated sites were used for these studies. Using a TiO2 slurry (0.1 g/L; Degussa P25) flowing down at a rate of up to 0.26 L/min over the inner surface of a glass tube surrounding a 1-kW medium pressure mercury lamp, more than 99% of MTBE in the synthetic samples, initially at 1 mg/L, was degraded within 90 min. The major degradation products from MTBE were tert-butyl alcohol, tert-butyl formate, and small amounts of acetone. However, the degradation of MTBE and its byproducts in contaminated groundwater samples was hindered significantly by dissolved metals such as Fe2+, chloride ions, and aromatic organic species. Integrating air stripping with gas-phase photocatalysis is an an effective alternative that would not be affected by the water chemistry. The reaction rates for MTBE degradation in the gas phase are orders of magnitude faster than in aqueous solution.     

Engineering Aspects of the Integration of Chemical and Biological Oxidation: Simple Mechanistic Models for the Oxidation Treatment

Oxidation processes can oxidize biorecalcitrant compounds into biodegradable intermediates, which in turn can be treated less expensively by a subsequent biological process. To design such a two-step (chemical+biological) process to treat poorly characterized wastewaters, it is useful to model the time evolution of characteristic global variables, chemical oxygen demand (COD) and biochemical oxygen demand (BOD), in order to develop a useful treatment strategy based upon these classical variables. We consider two simple model reaction networks, requiring three- and five-rate constants, respectively. The first model, proposed recently, involves conversion of a nonbiodegradable species, C, into a single biodegradable intermediate S. Here, biodegradable compounds are immediate kinetic products of oxidation. In general, it is not probable that a single recalcitrant compound undergoes a single-step reaction to CO2. However, when working with complex undefined wastewaters streams, single-step reactions may be used to simplify. The second new model corresponds to a lag time in BOD formation due to the necessity of multiple partial oxidations to reach a first biodegradable intermediate. The second network includes two intermediates, I and S, which are, respectively, nonbiodegradable and biodegradable. We then compare model behavior with an unfortunately sparse literature on BOD and COD values versus time in chemical reactors, and demonstrate the convenience of the first model, and the occasional necessity of the second, which reflects the presence of early intermediates which are nonbiodegradable.     

Development of a Novel Internal Electrolysis System by Iron Connected with Carbon: Treatment of Nitroaromatic Compounds and Case of Engineering Application

The mixture of scrap iron and particle carbon, termed internal electrolysis, has been used in the pretreatment of industrial wastewater to improve the biodegradability. However, the clogging of fillings reduces treatment efficiency, and filling replacement is inconvenient in engineering application. This study developed a novel internal electrolysis system, in which iron and carbon were separately placed and connected with a wire. Results showed that the removal of paranitrophenol by iron was significantly enhanced by the connection of carbon. The removal by iron connected with carbon was approximately equivalent to that by iron contacted with carbon. The removal of nitrobenzene and the production of aniline proved the reduction in nitro to amino group. The sites for contaminant removal were found to be on iron surface rather than on carbon surface. The connection of carbon to iron facilitated the corrosion of iron and led to the formation of more Fe oxyhydroxide and the release of more electrons from iron, both of which attributed to contaminant removal. The engineering application using the novel internal electrolysis demonstrated an average chemical oxygen demand removal of 60% and a significant increase in wastewater biodegradability. This novel internal electrolysis system was preliminarily proved feasible and convenient.     

Cognitive-Behavioral and Humanistic Group Treatment for Children With Learning Disabilities: A Comparison of Outcomes and Process.

The authors of this study examined the outcomes and processes of 2 types of group treatment--cognitive-behavioral treatment groups (CBTG) and humanistic group therapy (HGT)--offered to 200 elementary schoolchildren in a center for students with learning disabilities in Israel. Results indicated that the addition of either type of group treatment to individual academic assistance was more effective than the latter alone on most measures. In fact, on the majority of measures, group treatment without academic assistance was more effective than just individual assistance. Finally, HGT was more effective than CBTG on most measures. Most of the outcomes were sustained at follow-up, and some even increased from termination to follow-up, although effect sizes were quite low. Process measures included the Client Behavior System and the therapist Helping Skills System, which were measured at 5 points in time. Differences between the 2 treatment types were revealed on both process measures, including differences in the growth curve of these behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Liquid Sodium Ferrate and Fenton’s Reagent for Treatment of Mature Landfill Leachate

As landfills mature, biodegradable matter in leachate is consumed and remaining compounds are increasingly recalcitrant. In this work, ferrate was compared to Fenton’s reagent for the purpose of removing nonbiodegradable organic compounds from mature leachate. Oxidation conditions (time, pH, and dose) were optimized to yield maximum organic removal using two leachate samples from 20- and 12-year-old solid waste cells. Results from this study demonstrated that Ferrate and Fenton’s reagent had similar optimum pH ranges (3–5), but different organic removal capacities, ranging from 54 to 79% of initial leachate organic contents. An advantage of ferrate was that it was effective over a wide pH range. Advantages associated with Fenton’s reagent include that it had higher organic removal capacity, produced more oxidized organic compounds (measured as chemical oxygen demand/dissolved organic carbon), and produced more biodegradable byproducts (measured as chemical oxygen demand/5-day biochemical oxygen demand). Finally, both treatments were found to attack larger molecules (>1,000?Dalton), as indicated by an increase in smaller molecule contribution to organic carbon.     

Fenton Process for Landfill Leachate Treatment: Evaluation of Biodegradability and Toxicity

The single Fenton or the Fenton process implemented in combined scheme as a posttreatment after the ferric chloride coagulation was applied for leachate collected from a real waste disposal site. Depending on the ratios of H2O2/chemical oxygen demand, H2O2/Fe2+, and pH, the Fenton oxidation or both the Fenton oxidation and the Fenton coagulation were involved in chemical oxygen demand reduction. The implementation of ferric chloride coagulation as a pretreatment stage or acidification of raw leachate did not result in the improvement of chemical oxygen demand reduction efficacy of the following Fenton process comparing with that obtained by the direct Fenton treatment of raw leachate. The direct Fenton treatment with a higher (3/1) H2O2/chemical oxygen demand ratio applied to raw leachate without pH preadjustment (H2O2/Fe2+ = 10/1), produced more oxidized organic compounds (measured as dissolved organic carbon/chemical oxygen demand ratio), more biodegradable by-products (measured as a 7-day biological oxygen demand/chemical oxygen demand ratio), and required a considerably lower dosage of NaOH for neutralization, making it preferable for the leachate treatment. Although up to a twofold reduction in the toxicity was observed after the overall Fenton process application, the treated leachate remained extremely toxic to Daphnia magna.     

Adsorption Characteristics of Oxide Coated Buoyant Media (ρs<1.0) for Storm Water Treatment. I: Batch Equilibria and Kinetics

Urban rainfall-runoff mobilizes and transports significant loads of metal species. Promulgation of National Pollutant Discharge Elimination System Phase II regulations has spurred development of Unit Operations and Processes (UOPs) Best Management Practices (BMPs) for control of metal species. Recent UOP designs provide both adsorption and filtration using engineered media such as manganese oxide coated polymeric media (MOPM). Divalent metal species adsorption onto a manganese oxide coated polymeric medium was evaluated through batch adsorption experiments using a flowthrough batch reactor. Freundlich isotherms were utilized to fit the experiment data. For the media examined, MOPM, adsorption is pH dependent and results indicate a favorable solute pH range of >6 for metal species adsorption. The relative adsorption affinity of MOPM for four divalent metal species typically found in storm water is Pb(II)>Cu(II)>Cd(II)>Zn(II). Adsorption rates were rapid for this flowthrough batch system with over 50% removal in the first 30 min and over 90% removal within 5 h at a surface loading rate of 500 mL/cm2?min. The pH drift patterns, due to surface complexation, during each experiment, coincided with the metal species removal rate curve. Study results indicated that the inclusion of a thin manganese coating can significantly increase media adsorption capacity. MOPM has a comparable adsorption capacity for the divalent metal species compared to other commercial and research media.