Coke Plant Wastewater Research Articles

Functional screening of a metagenomic library for genes involved in microbial degradation of aromatic compounds

A metagenomic approach was taken to retrieve catabolic operons for aromatic compounds from activated sludge used to treat coke plant wastewater. Metagenomic DNA extracted from the sludge was cloned into fosmids and the resulting Escherichia coli library was screened for extradiol dioxygenases (EDOs) using catechol as a substrate, yielding 91 EDO-positive clones. Based on their substrate specificity for various catecholic compounds, 38 clones were subjected to sequence analysis. Each insert contained at least one EDO gene, and a total of 43 EDO genes were identified. More than half of these belonged to new EDO subfamilies: I.1.C (2 clones), I.2.G (20 clones), I.3.M (2 clones) and I.3.N (1 clone). The fact that novel I.2.G family genes were over-represented in these clones suggested that these genes play a specific role in environmental aromatic degradation. The I.2.G clones were further classified into six groups based on single-nucleotide polymorphisms (SNPs). Based on the combination of the SNPs, the evolutionary lineage of the genes was reconstructed; further, taking the activities of the clones into account, potential adaptive mutations were identified. The metagenomic approach was thus used to retrieve novel EDO genes as well as to gain insights into the gene evolution of EDOs.

Treatment of coke plant wastewater by SND fixed biofilm hybrid system

In this article, coke plant wastewater was treated by a simultaneous nitrifying and denitrifying (SND) fixed biofilm hybrid system. The results showed that suitable parameters of the system were important for the performance of the bio-degradation system. The chemical oxygen demand (COD) removal efficiency in this system was satisfactory, higher than 94%, and ammonia nitrogen was higher than 95%. The effluent COD concentration could meet the discharge standard, except for very few situations. The results showed that a sufficient carbon source was important for making ammonia nitrogen concentration meet the discharge standard. Then the TN removal efficiency in this system can be brought higher than 94%. Dissolved oxygen (DO) is very important to the performance of the SND bio-degradation system, and the suitable DO is about 3.5–4.0 mg/L at the forepart of reactor. In addition, the performance of the system was almost not affected by pH value. The results show that the system is feasible to treat coke plant wastewater.

Ultrasonic Decomposition of Ammonia-Nitrogen and Organic Compounds in Coke Plant Wastewater

The investigations of the ultrasonic decomposition of NH3-N and organic compounds (i.e., CODCr) in coke plant wastewater are presented in this work. The process parameters were controlled with respect to the presence (or absence) of air atmosphere, initial pH value, initial concentration, and ultrasonic power density in the process of ultrasonic decomposition. It is noted that the ultrasonic removal efficiencies for both the NH3-N and the CODCr were increased in the presence of the air atmosphere and significantly affected by the initial pH value. The removal efficiencies increased with increasing the ultrasonic power density while they decreased with increasing the initial concentration. The effects of n-butyl alcohol as an effective OH radical scavenger on the removal efficiencies indicates that the ultrasonic decomposition of the NH3-N was carried out mainly via the mechanism of thermal decomposition in cavitation bubbles or in the interfacial region, whereas the ultrasonic decomposition of the CODCr mainly resulted from the reactions with OH radicals in the bulk solution. The GC/MS analysis indicates that most of the organic compounds in the wastewater were effectively destroyed by ultrasound.

Treatment of coke plant wastewater by A/O fixed biofilm system

Coke plant wastewater was treated by an anaerobic-aerobic (A/O) biofilm system. A lab-scale experiment, during which semi-soft media were packed in both the anaerobic and the aerobic reactors, was carried out. The influence parameters, such as HRT, C/N ratio, OLR, and the recycling flow rate on the performance of the system, were studied. The results showed that a sufficient carbon source was important to the performance of bio-degradation system. The COD removal rate increased from 64.15% to 83.28% by raising C/N in wastewater from 2.5 (no external carbon source) to 5. But the effluent COD concentration was still a little higher than the discharge standard. In order to make it meet the discharge standard, a deep treatment, coagulation, was applied, which was proved as an effective method. Then the effluent COD concentration can be brought to lower than 200 mg·L−1. The NH4-N removal rate in this system was satisfactory, being higher than 99%. In addition, it was almost not affected by both C/N ratio and coagulation treatment. The results show that the system is feasible to treat coke plant wastewater.

Treatment of organic pollutants in coke plant wastewater by the method of ultrasonic irradiation, catalytic oxidation and activated sludge

The paper deals with the degradation of the organic pollutants in coke plant wastewater by the combination process of ultrasonic irradiation, catalytic oxidation and activated sludge. The effect factors of ultrasonic irradiation on the degradation of the organic pollutants such as saturating gas, initial pollutant concentration, ultrasonic power density, the category and consumption of catalyst were investigated. The results indicate that putting the saturating gas into the reaction solution in the process of the ultrasonic irradiation, low COD initial concentration and high ultrasonic power density are the favorable conditions for their degradation. Compared with single activated-sludge process, co-approach of ultrasonic irradiation and activated-sludge can greatly increase the COD degradation efficiency. When the wastewater was firstly treated by ultrasonic irradiation process and then followed by activated-sludge process for 240 min, respectively, the COD degradation efficiency increased by 48.29–80.54%. Additionally, when 3.0 mmol/l of ferrous sulfate was added into the ultrasonic irradiation process, the COD degradation efficiency was as high as 95.74%, 63.49% higher than that of the activated-sludge approach alone.

Treatment of coke-plant wastewater by biofilm systems for removal of organic compounds and nitrogen

Coke-plant wastewater was treated by an anaerobic–anoxic–aerobic (A 1–A 2–O) biofilm system and an anoxic–aerobic (A/O) biofilm system, respectively. At same or similar levels of hydraulic retention time (HRT), the two systems had almost identical chemical oxygen demand (COD) and NH 3 removals, but a different organic-N removal. Set-up of an acidogenic stage benefited for the removal of organic-N and the A 1–A 2–O system was more useful for total nitrogen removal than the A–O system. HRT did not have a substantial effect on the COD and NH 3–N removal efficiencies, but considerably influenced the organic-N removal and distribution of oxidized nitrogen in the final effluent. The GC/MS analysis demonstrated that some refractory compounds were decomposed at the acidogenic stage and resulted in the production of some intermediates, which were more readily degraded in the subsequent aerobic stage. Hence, the A 1–A 2–O system had better effluent quality than the A–O system in terms of effluent composition.

Bioaugmentation as a tool to enhance the removal of refractory compound in coke plant wastewater

Pollution caused by coal conversion wastewater has been a severe problem for decades in China due to the use of coal as the main energy source. An aerobic–anoxic–oxic (A1–A2–O) system was developed for treating coke plant wastewater and good results were obtained. GC/MS analysis indicated that the main ingredients of the effluent were aromatic and heterocyclic compounds, alkanes and phthalic acid esters etc. Bioaugmentation with specialized microorganism could be a powerful tool to improve the wastewater treatment processes. In this study, quinoline, which was poorly removed by the A1–A2–O system, was chosen as a target pollutant, and a quinoline-degrading bacterium, identified as Burkholderia pickettii was used as bioaugmentation microorganism. The feasibility of bioaugmentation in combination with A1–A2–O system was investigated. The performance of the A1–A2–O system and the contribution of each stage to COD removal were investigated. The contribution of anaerobic, anoxic and oxic reactors to COD removal was 25, 16 and 59%, respectively. The results of bioaugmentation experiments showed that the oxic reactor, to which the aerobic microorganism was added, was the best location of bioaugmentation in the A1–A2–O system. Bioaugmentation could be used as an efficient and effective method of improving the removal efficiency of recalcitrant organic compounds from industrial wastewater.

Development of nanofiltration/steam stripping sequence for coke plant wastewater treatment

The present work proposes the optimisation of an integrated process that consists in the coupling of Nanofiltration (NF) with Steam Stripping for the treatment of ammoniacal wastewaters contaminated by cyanides ions and phenols. These wastewaters are fractionated by NF into an ammonium concentrate and an ion-containing permeate stream. The concentrates are further fractionated in the steam stripping column. The NF experiments were performed with a DSS plate and frame Lab-Unit 20, equipped with a HR-98-PP membrane. The NF experiments were run in concentration mode to optimise the concentrate ammonium content/permeate flux as a function of water recovery ratio (RR). The optimisation of the NF/steam stripping integrated process was carried out with a sequential process simulator. The optimisation study showed that the NF should work at a recovery ratio of 40%. At this RR the ammonium can be efficiently concentrated and purified from cyanides at reasonable permeate flowrates. The column steam consumption was also optimised as a function of the NF concentrates flowrate. The integrated process leads to an increase of the stripping efficiency and to significant energy savings (0.698 EURO/m 3 treated water).

Degradation of tetracyanonickelate (II) by Cryptococcus humicolus MCN2.

A new yeast strain capable of degrading free and metallocyanides was isolated from coke-plant wastewater. The isolated strain designated MCN2 was identified as Cryptococcus humicolus by 26S rDNA sequencing and phylogenetic analysis. During growth of the isolate with KCN as a sole nitrogen source, formamide and formic acid were found as transient intermediates by [(13)C]nuclear magnetic resonance analysis and ammonia accumulated as a final product in the culture medium. The strain MCN2 could degrade high concentrations of tetracyanonickelate (II) (K(2)Ni(CN)(4), TCN) up to 65 mM CN within 60 h when a sufficient amount of glucose was supplied as a carbon source. The maximal degradation rate of TCN was 2.5 mM CN h(-1) at the initial concentration of 51 mM CN.

Degradation of tetracyanonickelate (II) by Cryptococcus humicolus MCN2

A new yeast strain capable of degrading free and metallocyanides was isolated from coke-plant wastewater. The isolated strain designated MCN2 was identified as Cryptococcus humicolus by 26S rDNA sequencing and phylogenetic analysis. During growth of the isolate with KCN as a sole nitrogen source, formamide and formic acid were found as transient intermediates by [ 13C]nuclear magnetic resonance analysis and ammonia accumulated as a final product in the culture medium. The strain MCN2 could degrade high concentrations of tetracyanonickelate (II) (K 2Ni(CN) 4, TCN) up to 65 mM CN within 60 h when a sufficient amount of glucose was supplied as a carbon source. The maximal degradation rate of TCN was 2.5 mM CN h −1 at the initial concentration of 51 mM CN.

Hybrid neural network modeling of a full-scale industrial wastewater treatment process.

In recent years, hybrid neural network approaches, which combine mechanistic and neural network models, have received considerable attention. These approaches are potentially very efficient for obtaining more accurate predictions of process dynamics by combining mechanistic and neural network models in such a way that the neural network model properly accounts for unknown and nonlinear parts of the mechanistic model. In this work, a full-scale coke-plant wastewater treatment process was chosen as a model system. Initially, a process data analysis was performed on the actual operational data by using principal component analysis. Next, a simplified mechanistic model and a neural network model were developed based on the specific process knowledge and the operational data of the coke-plant wastewater treatment process, respectively. Finally, the neural network was incorporated into the mechanistic model in both parallel and serial configurations. Simulation results showed that the parallel hybrid modeling approach achieved much more accurate predictions with good extrapolation properties as compared with the other modeling approaches even in the case of process upset caused by, for example, shock loading of toxic compounds. These results indicate that the parallel hybrid neural modeling approach is a useful tool for accurate and cost-effective modeling of biochemical processes, in the absence of other reasonably accurate process models.

Anoxic degradation of nitrogenous heterocyclic compounds by acclimated activated sludge

Batch experiments were conducted to investigate anoxic biodegradation of five refractory nitrogeneous heterocyclic compounds, i.e. pyridine, indole, quinoline, isoquinoline, 2-methyl quinoline, in coke plant wastewater. These compounds were effectively degraded by the denitrifiers in acclimated activated sludge within 60 h. The degradation rate was dependent upon chemical structures in the order: pyridine>indole>quinoline>2-methyl quinoline>isoquinoline. Denitrification was a zero-order reaction, and the denitrification rate of individual compounds had a linear relationship with its corresponding molecular connectivity index.

99/01577 Biological nitrogen removal from coke plant wastewater with external carbon addition : Lee, M. W. and Park, J. M. Water Environ. Res., 1998, 70, (5), 1090–1095

99/01577 Biological nitrogen removal from coke plant wastewater with external carbon addition : Lee, M. W. and Park, J. M. Water Environ. Res., 1998, 70, (5), 1090–1095

99/00803 Operational control of coke plant wastewater nitrification system

99/00803 Operational control of coke plant wastewater nitrification system

Biological nitrogen removal from coke plant wastewater with external carbon addition

Coke plant wastewater containing high concentrations of ammonia and toxic compounds such as phenol and cyanide was treated using a biological nitrogen removal (BNR) system comprising carbon removal, nitrification, and dentrification stages. The objective of this study was to investigate the feasibility of complete ammonia removal from the coke plant wastewater using a sequential BNR process with external carbon addition. Sodium acetate was introduced as an external carbon source to the denitrification stage after oxidation of phenol and other carbonaceous compounds in the carbon‐removal stage. The efficiency of denitrification was strongly affected by the loading rate of the external carbon source, and its optimal rate was determined based on the ratio of chemical oxygen demand to nitrate‐ and nitrite‐nitrogen (COD:NOx‐N) of the denitrification stage. The overall removal efficiency of major soluble pollutants in the wastewater was greater than 95% in the BNR system. When a step input of phenol was introduced to check the stability of the overall system, the nitrification was markedly inhibited because of the incomplete degradation of phenol in the carbon‐removal stage. However, after this brief inhibition, the nitrification stage recovered to its normal efficiency within 18 days.

98/03393 Removal of ammonia from coke-plant waste-water by using synthetic zeolite: Singh, G. and Prasad, B. Water Environ. Res., 1997, 69, (2), 157–161

98/03393 Removal of ammonia from coke-plant waste-water by using synthetic zeolite: Singh, G. and Prasad, B. Water Environ. Res., 1997, 69, (2), 157–161

Coke plant wastewater treatment by fixed biofilm system for COD and NH 3-N removal

Coke plant and coal gasification wastewater have similar characteristics. There are high concentrations of ammonia and organic compounds especially refractory and inhibitory organics in them. Coal is the main energy resource in China hence pollution caused by coke plant and coal gasification wastewater has been severe for decades. The anaerobic-anoxic-oxic (A 1-A 2-O) fixed biofilm system was used for coke plant wastewater treatment in this study. The experimental results showed that this system was efficient and stable in NH 3-N and COD reductions. The effluent NH 3-N and COD were 3.1, 114 mg/l with removal efficiencies of 98.8 and 92.4%, respectively, when the total HRT of the whole system was 31.6 hours. Microorganisms were enumerated and organic transformation in the system was analyzed by GC/MS equipment. Batch tests were also conducted and it was found that anaerobic treatment of coke plant wastewater differed from anoxic treatment. Biodegradable phenolics were removed at lower efficiencies while complicated and high molecular weight organics were removed at higher efficiencies by anaerobic treatment in comparison with anoxic treatment. The biodegradability of anaerobic effluent was higher than that of anoxic effluent.

98/00752 Methods for improving biochemical treatment of coke plant wastewater

98/00752 Methods for improving biochemical treatment of coke plant wastewater

Comparison between Anaerobic-Anoxic-Oxic and Anoxic-Oxic Systems for Coke Plant Wastewater Treatment

Coke plant wastewater produces severe pollution throughout China because coal is the main energy resource. The anoxic-oxic (A2-O) system can be used to treat this type of wastewater for simultaneous removal of NH3-N and COD. A comparative study between an anaerobic-anoxic-oxic (A1-A2-O) system and an A2-O system for coke plant wastewater treatment under the same operational conditions was undertaken to examine removal efficiencies of COD and NH3-N, denitrification performance, and transformation of organic pollutants in each system. The experimental results showed that the A1-A2-O system was comparatively more effective not only in nitrification but also in denitrification performance. The total NH3-N removal efficiency and the anoxic NOx-N removal rate of the A1-A2-O system were about 20% higher and more than twice that of the A2-O system, respectively. Coke plant wastewater subjected to anaerobic treatment resulted in less inhibitory effect on the subsequent nitrification process, and provided a more biodegradable and suitable carbon substrate for denitrifying bacteria. The anaerobic stage played an important role in nitrogen reduction in coke plant wastewater treatment.

Kinetics of phthalic acid ester degradation by acclimated activated sludge

Activated sludge obtained from a coke-plant wastewater treatment plant was acclimated and used as seeding microbes to investigate the kinetics of biodegradation of di- n-butyl phthalate (DBP), one of the most frequently identified phthalic acid esters in diverse environments and the most widely used plasticizer in China. DBP biodegradation conformed to the first-order model with respect to its concentration and the rate constant was independent of the initial concentration when the initial DBP concentration was less than 200 mg/litre.