Performance evaluation and mathematical modelling of granular activated carbon biofiltration in wastewater treatment

Biological filtration is an effective technique for removing organic matter from wastewater. The performance of a biofilter can be influenced by a range of operational conditions. In this study the performance of biofilters was investigated for the influence of filter media depth, influent concentrations, filtrations rates and backwashing. The results show that performance of GAC filters decreased with shallower filter bed depths. In addition, the GAC performed better at lower influent concentration and lower filtration rates. The daily backwash adopted to avoid the physical clogging of the biofilter did not have any significant effect on the organic removal efficiency of the filter. The concentration, activity and characteristics of the biomass are quantified and described. A mathematical model was developed to simulate the organic removal of the GAC biofiltration system. The performance of the GAC filter under different influent organic concentration levels, filtration rates and filter bed depths was adequately simulated by the mathematical model developed for this study.     

Sand filtration of wastewater for tertiary treatment and water reuse

The performance of rapid sand filters was evaluated in three tertiary wastewater treatment plants in the State of Kuwait. These plants are located at Ardiya, Rikka and Jahra, and receive municipal wastewater flows of 220,000, 95,000 and 42,000 m³ d⁻¹, respectively. The Ardiya plant uses a two-stage activated sludge process for the secondary treatment of wastewater whereas both the Rikka and Jahra plants use the extended aeration process. Daily records were obtained from each plant over a period of 1 year, and the efficiency of the tertiary sand filters was determined based on reductions in SS, VSS, BOD, and COD. Analysis of these records showed that the secondary-treated effluent quality is highly variable. Seasonal variations were observed due to nitrification and denitrification that enhance the production of nitrogen gas and carry over of sludge solids in the effluent during summer, causing more frequent backwashing of the filters. The data were also statistically analyzed using the ANOVA program. The results obtained indicated significant improvements, at 95% and 99% significance levels, in solids (SS, VSS) and organics (BOD, COD) removal by sand filtration. They also showed that, in addition to improving effluent quality, the tertiary filtration played an important role in the stability of effluent quality so as to dampen variations in the quality of secondary-treated effluent. The tertiary effluent consistently satisfied the water quality requirements for irrigation.     

Applications of hydrothermal electrolysis for conversion of 1-butanol in wastewater treatment

Hydrothermal electrolysis of organic compound in the presence of electrolyte was conducted for a woody biomass model compound. The reaction behavior of 1-butanol as a woody biomass model compound was studied in subcritical conditions at 200-250 °C and 8-12 MPa with a batch autoclave. The autoclave volume was 500 mL and equipped system with agitation stirrer, electric current control, electric heating and temperature control and a pressure gauge. The chemical species in aqueous products were identified by gas chromatography mass spectrometry (GC-MS) and quantified using gas chromatography flame ionization detector (GC-FID). The gaseous products were analyzed by gas chromatography with a thermal conductivity detector (GC-TCD). The effects of reaction temperature, pressure and applied constant current on the conversion process of 1-butanol were presented. The main products from the conversion of 1-butanol were butanal, butyric acid, hydrogen and carbon dioxide. Additionally, the values of reaction rate constant for butanal and butyric acid formation were calculated at 200 and 250 °C by kinetic study.     

Biofilter modeling for waste air treatment: Comparisons of inherent characteristics of biofilter models

The types of biofilter modeling may be primarily classified in accordance with whether a biofilm is differentiated from other phases in each model. It may be a secondary classification with regard to biofilter-modeling whether sorption volume and/or adsorption are adopted as reservoirs or not. Thirdly, biofilter models are classified as to whether adsorption is assumed to exist through gas phase and/or a biofilm. Among all the biofilter-models of previous investigators all model-components including gas phase, a biofilm, sorption volume and adsorption surface are considered only in the model of Lim. Since his model does not require a numerical solution but an algebraic solution to describe the concentration of organic pollutants in waste-air-streams along the height of a biofilter even under unsteady-state conditions, it satisfies the condition of simplicity that is one of the important model requirements. In spite of its simplicity, Lim's model predictions are fairly good to fit Hodge and Devinny’s experimental data.     

Technical efficiency and cost analysis in wastewater treatment processes: A DEA approach

In light of the growing importance of water reuse as an alternative source of water resources in many regional areas, the objective of this paper is to analyse the efficiency of wastewater treatment plants as a basic requisite to improve the potential of the water reuse. The analytical benchmarking methodology Data Envelopment Analysis (DEA) is used to calculate efficiency measurements. An efficiency index is obtained for each plant by means of mathematical programming techniques, aiming to minimise the inputs used in the water treatment process. This indicator is used as a reference to analyse plants' activity through a series of variables including the size of the plant or its cost structure. Given the importance of wastewater treatment in the Valencia Region (Spain), empirical research has been carried out for 338 plants located in this area. We verify the fact that the largest plants run more efficiently than smaller plants, as was to be expected. At the same time, there is evidence that a series of representative variables in the treatment process are clearly linked to efficiency. Maintenance and waste management costs are the most important factors to explain the differences between plants in terms of efficiency. Finally, the benchmarking methodology (Data Envelopment Analysis) is confirmed as a very useful management tool for the study of wastewater sector.     

Effect of Media on Biofilter Performance Following Ozonation of Secondary Treated Municipal Wastewater Effluent: Sand vs. GAC

Ozone has been shown to be effective in the transformation of several chemicals of emerging concern that escape the wastewater treatment process, but there is concern whether toxic transformation products are formed. Two parallel biofilter columns with granular activated carbon (GAC) and filter sand following a pilot-scale ozone unit to treat secondary treated municipal wastewater were studied. Results show reduced wastewater genotoxicity following ozonation and further reduction following biofiltration. The BAC biofilter outperformed the sand biofilter in terms of reduction in both organics and genotoxicity. Biofilter performance correlated with biological indicators (dissolved oxygen reduction and effluent E. coli counts) but not with ATP bioactivity measurements. Limited bacterial (E. coli) regrowth was observed in treated effluent from both biofilters.     

Application of characterization procedure in water and wastewater treatment by Adsorption

The background organics in water and wastewater are necessary to fractionate into groups or components according to the difference in adsorbability. In this study, the background organics were fractionated in terms of the adsorptive strength described by the Freundlich isotherm constants k and n with the assumption that the fractionated components differ in the value of k but have the same value of n based on the IAST (Ideal Adsorption Solution Theory) using binomial concentration distribution. A simple characterization for water and wastewater with a certain amount of DOC in terms of adsorbability was applied to three types of organic mixtures contained in different water sources. The composition of each organic mixture was successfully evaluated to describe the IAE (Integral adsorption experiments) data of the total organic carbon by using this characterization procedure. Batch experiments as well as the membrane-PAC hybrid system experiments were conducted with three different types of PACs.     

Disinfection of spring water and secondary treated municipal wastewater by TiO2 photocatalysis

The photocatalytic disinfection of spring water and secondary treated municipal wastewater by means of UV-A irradiation over TiO₂ suspensions was investigated. Water samples were taken from a spring supplying water to the city of Chania, Western Crete, Greece, while wastewater samples were collected from the outlet of the secondary treatment of Chania municipal wastewater treatment plant. The effect of various operating parameters such as photocatalyst type (rutile, anatase, mixture of anatase and rutile) and concentration (0.5-1 g/L), contact time (up to 60 min) and sample pH (6-8) on the disinfection as assessed in terms of faecal indicator microorganisms (total coliforms and enterococci) inactivation was examined. A commercially available Degussa P25 TiO₂ powder, consisting of 75% anatase and 25% rutile, was found substantially more active than pure anatase or rutile for both groups of bacteria inactivation which increased with increasing contact time and catalyst concentration, whereas small pH changes had little effect on destruction. For both groups of bacteria tested, inactivation followed a first order kinetic expression with the gram positive Enterococcus sp. being considerably more resistant to photocatalytic disinfection than total coliforms.     

Fenton法及类Fenton法在污水处理方面的研究与应用

Fenton试剂通过H2O2和Fe2+作用产生.OH,因而具有极强的氧化能力,在治理环境污染方面得到了广泛的应用。为了改善Fenton法中H2O2利用率低等缺点,越来越多的研究者将Fenton法与其它方法联/并用,极大提高了Fenton的催化效率。作者主要介绍了Fenton法及类Fenton法催化原理及其在污水及污染物处理方面的应用。     

超声波在废水处理中的应用

介绍了超声波在废水处理中的应用,它能使废水中的污染物得有效降解,而展示其应用前景。     

Catalytic hydrothermal treatment of pharmaceutical wastewater using sub- and supercritical water reactions

Application of subcritical and supercritical water technology for destruction of pharmaceutical compounds (carbamazepine, metoprolol and sulfamethaxazole) was investigated. The experiments were conducted inside batch reactor at a temperature ranging from 473 to 773 K and with different residence times of 5 to 50 min. The results show that carbamazepine, metoprolol and sulfamethaxazole are destructed by 90.27%, 99.99% and 98.84% after a 20 min exposure to 623 K, 673 K and 573 K, respectively. In comparison with the conventional methods of pharmaceutical waste treatment, the current technology provides a higher destruction efficiency (approximately 90–100%) which is achievable in shorter durations. NaOH and CuSO₄·5H₂O were also applied as catalysts in the temperature range of 473 K to 723 K. Comparing these catalysts, CuSO₄·5H₂O demonstrates a higher destruction efficiency, especially at lower temperatures. Based on the proposed pathway, the products of destructioncan be classified as environmentally-friendly compounds. The results show that this technology can be used as a green alternative for efficient removal of pharmaceutical compounds from wastewater streams.     

Preliminary bench and pilot plant experiences for On-board wastewater treatment by ozone

This paper presents results obtained during a series of bench and pilot plant experiences on the utilization of ozone technology to treat sanitary wastewater coming from boats. Data on ozone solubility in soft water and sea water in a bench reactor were obtained. The analysis of the abatement of BOD, Total Coliforms, UV-absorbance and other parameters were performed on simulated saline and soft on-board wastewater considering increasing batch reactor retention time. The results indicated that the best abatement was obtained in saline wastewater with about 70% BOD and a 95% Total Coliform reduction in 30 minutes; further UV spectra have shown a sensible abatement of the absorbance readings. Pilot plant experiences on a saline wastewater confirm the potential possibility to treat hygienic on-board wastewater with ozone technology.     

声化学技术处理有机废水的研究进展

对近年来国内外兴起的超声波降解技术作了较为全面的概述,主要针对有机废水的处理,分别就超声波工作原理、超声降解机理、超声波降解技术的研究成果及技术优化和超声降解技术的展望及今后研究方向等作了较为系统的介绍。     

催化臭氧化技术在废水处理中的应用

阐述了均相催化臭氧化和非均相催化臭氧化技术在废水处理中的应用研究进展,并提出了技术发展趋势与存在的问题。非均相催化臭氧化技术是现代催化技术与环境化学处理技术的组合,其中催化剂具有活化臭氧、提高臭氧氧化降解能力的作用。该技术具有降解能力强、效率高、不产生二次污染等优点,将在环保领域发挥越来越大的作用。     

过程工业水分配网络的研究进展

回顾了水分配网络的发展历程,介绍了水分配网络的用水网络和废水处理网络2个子系统的研究进展,阐述了图解方法、数学优化法等用水网络综合方法的发展状况,并对水分配网络设计中多杂质和热集成等方面的问题进行了展望。     

Characterization and application of chars produced from pinewood pyrolysis and hydrothermal treatment

Two types of pinewood chars, hydrothermal char (H300) and pyrolytic char (P700) from biomass-to-energy conversion were characterized and used as adsorbent for the copper removal from aqueous solution. The result showed that the pinewood underwent a deeper carbonization during pyrolysis process and more activated sites available and stable carbon-oxygen complex existed after hydrothermal treatment. Comparing with raw pinewood, hydrothermal treatment increased 95% total oxygen-containing groups (carboxylic, lactone and phenolic group) while 56% oxygen-containing groups decreased after pyrolysis process. SEM analysis indicated that both hydrothermal and pyrolytic processes developed rough surface with new cavities on the chars, and the BET surface area were 21 and 29 m²/g for H300 and P700, respectively. Although H300 had lower surface area, its adsorption capacity for copper was much higher than P700 since ion-exchange reaction was the predominant removal mechanism by H300, while physical adsorption dominated by P700. The adsorption data could be well described by Langmuir isotherm model for copper onto both H300 and P700.     

AAOO-Fenton氧化工艺处理焦化废水

介绍了焦化废水的特点以及AAOO-Fenton氧化工艺处理济钢焦化废水的运行效果。蒸氨废水经AAOO工艺处理后,再经过高效混凝沉淀及Fenton氧化深度处理,出水水质达到了国家二级排放标准。     

陶瓷膜在染料及漂染废水处理中的应用

考察了以陶瓷膜为过滤介质的旋叶压滤机对絮凝后的废水进行处理的过滤速率及其影响因素,进行了动态过滤与终端过滤的比较,以及陶瓷膜与有机膜在废水处理效果上的对比研究。     

Optimal design of reverse-osmosis networks for wastewater treatment

An optimization study of reverse-osmosis networks (RON) for wastewater treatment has been carried out by describing the system as a nonconvex mixed-integer nonlinear problem (MINLP). A mixed-integer linear problem (MILP) is derived from the original nonlinear problem by the convex relaxation of the nonconvex terms in the MINLP to provide bounds for the global optimum. The MILP model is solved iteratively to supply different initial guesses for the nonconvex MINLP model. It is found that such a procedure is effective in finding local optimum solutions in reasonable time and overcoming possible convergence difficulties associated with MINLP local search methods. Examples of water desalination and wastewater treatment from the pulp and paper industry are considered as case studies to illustrate the proposed solution strategy.     

Fenton试剂处理邻氯苯胺废水的研究

采用Fenton试剂氧化处理含邻氯苯胺的生产废水,研究了H2O2,Fe2+投加量以及反应体系pH值对废水COD去除率的影响。通过实验,确定了Fenton试剂处理该废水的最佳操作条件:在pH值为3,FeSO4.7H2O的投加量为Fe2+在废水中的质量浓度达到0.56 g/L,每升废水中H2O2(质量分数30%)投加量18 mL时,废水的COD去除率达到72.9%。