Search

Refereed/Peer-reviewed While laccase oxidation is a novel and promising method for treating arsenite-containing wastewater, the high cost and unsustainability of commercially available enzymes indicate a need to investigate more cost-effective viable alternatives. Here, a microorganism sustained secrete laccase-straw oxidation system (MLOS) was established and subsequently evaluated for the removal of As(III). MLOS showed efficient biological As(III) oxidation, with an As(III) removal efficiency reaching 99.9% at an initial As(III) concentration of 1.0 mg·L−1. IC-AFS and XPS analysis showed that As(III) was partially oxidized to As(V), and partially As(III) adsorbed on the surface of rice straw. FTIR analysis revealed that hydroxyl, amine and amide groups were all involved in the As(III) removal process. SEM-EDS demonstrated that the surface structure of rice straw was destroyed following Comamonas testosteroni FJ17 (C. testosteroni FJ17) treatment, and the metal ions binding sites of rice straw were increased resulting in elemental arsenic being detected on the material surface. Molecular docking revealed the interaction between key residues of laccase and As(III). Laccase activity was negatively correlated with Cu(II) concentration in the As(III) oxidation. EEM showed that humic-like acids were also involved in the interaction with As(III). Overall, a MLOS derived from biomass waste has a significant potential to be developed as a green and sustainable technology for the treatment of wastewater containing As(III).

Common Effluent Treatment Plants (CETP) are intended for effective treatment of effluent discharged from industrial clusters aiming to support the small/medium scale industries that are deprived of enough resources and technological ability to treat their effluent individually. The present review discusses various processing steps in a typical CETP and their design considerations. The various drawbacks of existing CETPs have been discussed with the need for requirement of novel treatment techniques for their reformation. The different novel approaches discussed include improved coagulation-flocculation, advanced oxidation processes like electrochemical oxidation, cavitation, Fenton, ozonation and photocatalysis. Additionally, possible improvements in the biological treatment methods have also been discussed. Possible applications of bioremediation methods like phytoremediation, constructed wetlands, microbial fuel cells, use of fungi and algae have been highlighted. Membrane technologies and physicochemical treatments coupling with biological oxidation have also been described. For each method, mechanism involved, recent advances and possible recommendations for operating conditions have been provided. The economic aspects of the effluent treatment have also been discussed to aid the transformation of existing CETPs. Overall, the review clearly brings out the important novel techniques having potential to be applied in the existing CETPs and modifications in the existing approaches for their performance enhancement.

The chemical processes occurring in the animal body under pathological conditions are of interest to researchers. The objective of the research was to study the indicators of lipid peroxidation and antioxidant activity in horses infested with helminthiases and treated with anthelmintic paste with an antioxidant. The study has proved the role of parasitic infestation in accelerating the processes of free radical oxidation, which is manifested by a decrease in the light sum of radicals (36.62-39.21), the maximum luminous intensity (6.13-6.98) and antioxidant activity (5.65-6.2) at the start of the research. Chronic invasion increases the concentration of under-oxidized products up to 38.59, and the rate of initiating free radical oxidation – up to 6.95, the values of antioxidant activity being stably low (5.51-5.91). An important role in the regulation of lipid peroxidation in horses during helminthiases, as well as in the process of deworming, is played by the antioxidants contained in anthelmintic preparations. The antioxidant santohin included as a compound in the «Alezan» preparation suppresses enhanced peroxidation and activates the antioxidant protection of the body, which is reflected in a decrease in the light sum of the radicals to as low as 26.73, a maximum luminous intensity to – 3.76, and an increase in antioxidant activity – up to 7.16.

Various studies concerning sanitary landfill leachate (SLL) characteristics and toxicity identified the presence of endocrine disrupting chemicals (EDCs). A review of the detected EDCs in SLL was performed, in which the 12 most frequent EDCs identified in sanitary landfill sites over the world were ranked: BPA, DBP, DEHP, DEP, NP, BBP, DOP, DMP, 4OP, DiBP, DTBP and nicotine. The presence of these compounds is related to the activities on the dumping site, especially by the presence of plastic and personal care products, insecticides and cleaning agents in the waste bulk. Many diseases in human and animals have been associated with exposure to EDCs, as examples can be cited: disorder in metabolic processes that might end in diaseases, reduction of fertility, bioaccumulation and a high cancer potential. Among the treatment strategies applied to SLL degradation, processes based on Fenton reaction have received increasing attention due to its non-selective oxidation performed by hydroxyl radicals (•OH). Thus, they are able to oxidize/mineralize compounds which are not removed in conventional wastewater treatments. Degradation pathways and byproducts produced after the oxidative process may provide important information around the applicability of these techniques. Integrated treatments are also studied to obtain biosafety of treated wastewater samples. For the SLL treatment, the most employed strategy coupled to Fenton-based processes is the biological oxidation. The integration strategy relies on the SLL characteristics, being two modalities allowed: Fenton-based processes followed by biological systems or the opposite one. Future researches are needed to advance our understanding of the behavior of EDCs in human and animals bodies, as well as its critic concentrations. Also, there still is a lack of research regarding the degradation pathway of EDCs by OH in a SLL matrix, the ecofriendly disposal of iron sludge, the handle of the chemical solution wastes and the economic aspects of these treatments in order to meet a large scale application of this technology. Therefore, these topics have been discussed in this review article.

Dissolved methane in the effluent of anaerobic wastewater treatment processes is unrecovered and released into the atmosphere as methane, a greenhouse gas. To prevent methane emissions from effluent, a post-treatment system consisting of two closed downflow hanging sponge (DHS) reactors for the recovery and biological oxidation of dissolved methane was developed. More than 99% of the dissolved methane was completely eliminated using this system under ambient temperatures for 1year. In this study, the methanotrophic community composition of the two closed DHS reactors was investigated. The performance of the closed DHS reactor was evaluated at different heights of the reactor in summer and winter. The clone libraries and T-RFLP analyses based on the pmoA gene revealed that type I and type II methanotrophs were present in the closed DHS reactors. Furthermore, type I methanotrophs showed wide diversity and contained uncultured phylogenetic clusters of methanotrophs (FWs and LWs), while type II methanotrophs were dominated by Methylocystis- and Methylosarcina-related clusters. The relative abundance of type II methanotrophs increased during winter. The type I methanotroph population dynamically changed with height of the reactor. These results demonstrate the important role of methanotrophs in removal of dissolved methane from upflow anaerobic sludge blanket effluent treating sewage. © 2017 Elsevier B.V., Embargo Period 12 months

Microbial action is the main pathway removing steroid estrogens (SEs) from both aerobic and anaerobic natural waters. The rate is influenced by other active substances present, particularly dissolved organic matter (DOM). DOM in natural surface waters has unstable components which undergo spontaneous photochemical oxidation, biological oxidation, chemical oxidation changes. How these changes influence the biosorption and bio-removal of SEs was the subject of this research. Photo oxidation-induced DOM increased the proportion of the fluorescence in area V, but biological oxidation and chemical oxidation caused fluorescence area V to decrease. All three oxidation processes can reduce the proportions of molecular weight (MW) > 5 kg·mol−1 and increase the proportions of MW 0.8, p ≤ 0.01) and SUVA254 (R > 0.8, p ≤ 0.01) by correlation matrix. Besides, fresh river fulvic acids (RFA) and aged RFA had the bigger mediating effect on E2 bio-removal under anaerobic conditions, and this imply that changes in aged DOM affected by other electron transfer groups in an anaerobic water environment. In anaerobic conditions, biosorption of E2 and binding action could cluster together with SUVA254, p(v), and 1 kg·mol−1 5 kg·mol−1.

Hydrocarbon substrates can be upgraded to high-value products through biological oxidation processes, whereby an oxygen moiety is inserted into the hydrocarbon backbone by microbes in a suitable bioreactor system such as a bubble column reactor (BCR). However, there is a need to understand the behaviour of the Sauter bubble diameter (D32) and gas hold-up ( Ɛ G ) in a simulated four-phase (air, water, hydrocarbon and microbes) system in the BCR. This study has investigated the impact of operational conditions, such as hydrocarbon concentration (HC), superficial gas velocity (UG) and yeast loading (SL) (using deactivated S. cerevisiae as test microorganism) on D32 and Ɛ G . It was found that D32 and Ɛ G were mainly affected by UG and SL, whereas HC had an insignificant impact on both D32 and Ɛ G . Any increase in UG (1–3 cm/sec) resulted in a significant increase in D32 and Ɛ G , due to the increase in the number of bubbles in the system. On the other hand, an increase in SL was found to result in D32 linearly increasing, which thereafter caused a decrease of Ɛ G in the system. This influence can be attributed to the yeast cells in the system affecting the fluid properties and the system hydrodynamics. The outcome of this work provides fundamental understanding of the impact of operating conditions (HC, UG and SL) on D32 and Ɛ G , which underpins the system hydrodynamics in a simulated four-phase hydrocarbon-based bioprocess.

Great progresses have been made to carry out Fenton oxidation under neutral or alkaline pH in which, nevertheless, organic acids and other acidic intermediates usually result in acidic Fenton effluent. To eliminate the classical neutralization step prior to biological treatment, acid-tolerant microbes were here screened and used for purification of acidic Fenton effluent to achieve pH increase and further COD (chemical oxygen demand) removal. The bacterial and fungal community diversity was analyzed before and after screening for acid-tolerant microbes. After screening the bacterial diversity sharply decreased while the fungal diversity at the genus level became richer, mainly including Phialemoniopsis (relative abundance 38.69%), Vanrija (20.08%), Hypocreaceae (18.44%) and Candida (14.74%). Acidic pH and residual H2O2 are the features of Fenton effluent; hence, effects of pH and H2O2 on the screened acid-tolerant microbes were investigated in the aspects of growth rate and oxygen uptake rate. The kinetic parameters, including YH–biomass yield coefficient; Kd–biomass decay coefficient; μm–specific maximum COD removal rate; Ks–half saturation constant for COD removal, of the acid-tolerant microbes using 1/5 YM (yeast extract and malt extract culture medium) as substrate at 25 °C were measured by respirometric methodology. In BAC (biological activated carbon) inoculated with acid-tolerant microbes to treat actual Fenton effluent, the average COD removal efficiency was 72% at HRT (hydraulic retention time) of 3 h and the effluent pH was above 6 after removing the dissolved CO2 by air stripping. This study will provide a basis for developing a new combined process including Fenton and biological oxidation without pH adjustment.

Energy consumption represents a significant part of the operative costs of a wastewater treatment plant but, with a correct design and a careful management model, there are important possibilities for its limitation. The proposed research presents a multi-step methodology for the evaluation of the energetic aspects of wastewater treatment, which was implemented on the largest facility in Italy (2.7 M population equivalents as organic load), managed by Societa Metropolitana Acque Torino (SMAT). The study initially took into account each phase of the process scheme, in order to obtain specific electricity consumption values for all the electro-mechanic devices. Data from tele-control system and direct measurements in field have both been acquired. The total electric energy demand of the plant was evaluated (66.78 GW h/y, about 50% from aeration in oxidation tanks). In account of large contribution the energy efficiency of the blowers was verified with positive results. Four specific energy consumption indexes were considered to carry out a critical analysis of SMAT wastewater treatment plant with other facilities performing biological oxidation processes and of a different order of magnitude about design capacity, and congruent values were obtained. The considered indexes related the electric energy demand to the equivalent population, to the volume of treated water and to the amount of removed COD and total Nitrogen. Furthermore the thermal energy demand of the plant was estimated (49.15 GW h/y, more than 93% from sludge line). An energy balance for the whole plant was finally evaluated, and some energy optimization solutions to decrease the corresponding costs were suggested.

Almost all present biological processes for treating municipal wastewater have been developed based on the philosophy of biological oxidation with high energy consumption and generation of waste sludge. Given such a situation, the fundamental question of what are the possible ways towards energy self-sufficient biological reclamation of municipal wastewater needs to be addressed urgently. Therefore, this review aims to offer a critical view and a holistic analysis of biological treatment processes with the focus on energy self-sufficiency which indeed is a game changer in the future technology development. The way towards energy self-sufficient operation of biological processes is to maximize energy recovery, while to minimize energy consumption. The examples of such process configurations known as A-B processes are thus discussed. Consequently, this review may offer in-depth insights into the possible directions towards the next-generation biological processes for municipal wastewater reclamation which should be designed as a water-energy-resource factory.

Anaerobik Amonyum Oksidasyon (Anammox) prosesi, 1995 yılında keşfedilen anaerobik ortamda Planctomycete bacteri grubunun aracılığı ile, NO2- elektron alıcısı olarak kullanıp amonyumu okside edip N2 gazına dönüştüren bir litoototrofik prosestir. Nitrit'i elektron alıcısı olarak kullanımı, Anammox uygulamalarından önce bir ön-kısmi nitrasyon prosesi gerektirir. Bugüne kadar, Anammox öncesi kısmı nitritasyon prosesi laboratuvar ölçeğinde ve gerçek büyüklükteki çalışmalarda çürütücü süzüntü sularının ekonomik olarak arıtılmasında başarı ile uygulanmış ve optimize edilmiştir. Ancak, evsel atıksu arıtmasında, Anammox uygulanması tüm dünyada hala sınırlıdır. Pek çok ülkede yerel Anammox aşı çamurunun eksikliği, Anammox bakterilerinin aşırı yavaş büyüme oranına sahip olması ve Anammox prosesi öncesinde Kısmi nitrifikasyonun gerekli olması, Anammox uygulamalarını sınırlamaktadır. Bu çalışma, esas olarak Türkiyede gerçek tesis işletme koşullarında atıksuyun kısmi nitrifikasyonunun incelenmesi ve Anammox türlerinin evsel nitelikli gerçek atıksudan kaynaklı aktif çamur kullanarak lokal olarak üretilmesi üzerine odaklanmıştır. Bu amaçla, iki (2) adet pilot ölçekli reaktörler, kısmı nitrifikasyon (KN) ve Anammox (AN) reaktörleri, Bursa Doğu Biyolojik Azot Giderim Atıksu Arıtma Tesisinde (AAT) kurulmuş ve Bursa Doğu AAT deki karışık aktif çamur ile aşılanmıştır. PN ve AN reaktörleri sırası ile 360 ve 425 gün boyunca işletilmiştir.Atıksuyun kısmi nitritasyonu pilot çalışması, çözünmüş oksijen, sıcaklık, pH, FA ve çamur yaş faktörlerinin PN verimliliğine olan etkisini göstermiştir. Atıksuyun kismı nitritasyonu stabil değildir. Tesis giriş suyu karakteriksiğinde olan değişikliklere bağlı olarak, geniş aralıklarda çıkış suyu kalitesinde dalgalanmalar olmuştur. Tüm çalışmaya göre, max. 1.2 civarında NO2--N:NH4+-N oranı, 1.1-1.2 mg/L DO, 20-24°C sıcaklık, 0.7-1.1 mg/L FA ve 4-5 gün SRT koşullarında elde edilebilir. Anammox için uygun olmayan, pek çok faz, düşük NO2--N:NH4+-N oranı ile sonuçlanmıştır. PN, evsel atıksuda Anammox uygulamaları için ana sınırlayıcı faktör olarak tanımlanmıştır. Evsel atıksuda iki aşamalı kısmi Nitritasyon-Anammox sistemlerinin kullanılması, gerçek uygulamaları için uygun bulunmamıştır.Türkiye'de ilk kez, gerçek tesis işletme koşullarında yerel aktif çamurdan anammox üretimi, başarılı bir şekilde gerçekleştirilmiştir. Anammox populasyonu DNA kopya numarası, başlangıçta karışık aktif çamurda 10^3 ng/ml iken 10^7 ng/ml seviyesine çıktı. Toplam azot giderim oranı, 96 mg N /gün Azot yükünde 89 mg N/gün seviyesine ulaştı, 425 gün işletme sonunda, giderim oranı %93 oldu. Anaerobic Ammonium Oxidation (Anammox) process, which was discovered in 1995 is a lithoautotrophic process mediated by a group of Planctomycete bacteria which oxidize ammonium to N2 gas using NO2- as electron acceptor under anaerobic conditions. The use of nitrite as an electron acceptor requires a preliminary partial nitritation process prior to Anammox applications. To date, partial nitritation followed by Anammox process has been successfully implemented and optimized for sidestream digester supernatant treatment in a cost-effective way both in laboratory-scale and full-scale studies. However, application of Anammox process for mainstrem sewage treatment is still limited in all over the world. The lack of local Anammox seed in most of the countries, extremely slow growth rate of Anammox bacteria and partial nitritation requirement of the process limit Anammox applications. This study mainly focused on to evaluate the partial nitritation of sewage under real plant conditions and to assess enrichment of Anammox species locally under real sewage treatment conditions. For this purpose, two (2) pilot scale reactors, partial nitritation (PN) and Anammox (AN) reactors, were installed in Bursa Doğu Biological Nutrient Removal STP in Turkey and inocculated with mixed activated sludge of Bursa Doğu STP. The PN and AN reactors were operated with sewage for 360 days and 425 days, respectively. Partial nitritation of sewage pilot study demonstrated the effect of dissolved oxygen, temperature, pH, FA and sludge age factors on PN efficiency. PN of sewage was not steady. The wide fluctuations occurred in effluent quality depending on the changes in plant influent characteristics. In the whole study, the NO2--N:NH4+-N effluent ratio could be obtained maximum around 1.2 under DO: 1.1-1.2 mg/L, temperature: 20-24°C, FA: 0.7-1.1 mg/L and SRT: 4-5 days. There were many periods resulted very low NO2--N:NH4+-N effluent ratio which is not proper for Anammox. PN was identified as the major limiting factor for mainstream sewage Anammox applications. The use of two-stage partial Nitritation-Anammox systems for mainstream was found unfeasible for real case applications. Anammox enrichment from local activated sludge was successfully achieved first time in Turkey under real plant conditions. Anammox population DNA copy number, which was initially 10^3 ng/ml in mixed activated sludge reached to the levels of 10^7 ng/ml. The total N removal rate reached to the level of 89 mg N/d for total N loading of 96 mg N /d with about 93% removal efficiency at the end of 425 days enrichment period. 108

The occurrence of discolored drinking water at customers’ taps, which is mainly caused by the deposition and release of iron (Fe) and manganese (Mn) in water distribution networks (WDNs), is a major worry for both customers and water companies. In this paper, two hierarchical fuzzy inference systems (FISs) to predict Fe and Mn accumulation potential in WDNs were developed. They were also able to indicate the causes of Fe and Mn accumulation potential failures. The FISs could be of great benefit to water resource engineers and drinking water supply companies in managing water discoloration.

Three different chemical oxidation processes were investigated in terms of their capability to degrade organic chemical components of real mature landfill-leachate in combination with biological treatment run in a Sequencing Batch Biofilter Granular Reactor (SBBGR). H2O2, H2O2 + UV and O3 were integrated with SBBGR and respective effluents were analyzed and compared with the effluent obtained from biological SBBGR treatment alone. In agreement with their respective oxidative power, conventional bulk parameters (residual COD, TOC, Ntot, TSS) determined from the resulting effluents evidenced the following efficacy ranking for degradation: SBBGR/O3 > SBBGR/UV + H2O2 > SBBGR/H2O2 > SBBGR. A more detailed characterization of the organic compounds was subsequently carried out for the four treated streams. For this, effluents were first subjected to a sample preparation step, allowing for a classification in terms of acidic, basic, strongly acidic and strongly basic compounds, and finally to analysis by liquid chromatography/high resolution mass spectrometry (LC/HR-MS). This classification, combined with further data post-processing (non-target screening, Venn Diagram, tri-dimensional plot and Principal Component Analysis), evidenced that the SBBGR/H2O2 process is comparable to the pure biological oxidation. In contrast, SBBGR/O3 and SBBGR/UV + H2O2 not only resulted in a very different residual composition as compared to SBBGR and SBBGR/H2O2, but also differ significantly from each other. In fact, and despite of the SBBGR/O3 being the most efficient process, this treatment remained chemically more similar to SBBGR/H2O2 than to SBBGR/UV + H2O2. This finding may be attributable to different mechanism of degradation involved with the use of UV radiation. Apart from these treatment differences, a series of recalcitrant compounds was determined in all of the four treatments and partly identified as hetero-poly-aromatic species (humic acids-like species). ? 2018 Elsevier B.V.

This study focussed on evaluating the effect of hydrogen sulfide (H 2 S) on biological oxidation of waste methane (CH 4 ) gas in compost biofilters, Batch experiments were conducted to determine the dependency of maximum methane oxidation rate (V max ) on two main factors; pH and moisture content, as well as their interaction effects. The maximum V max was observed at a pH of 7.2 with decreasing V max values observed with decreasing pH, irrespective of moisture content. Flow-through columns operated at a pH of 4.5 oxidized CH 4 at a flux rate of 53 g/m 2 /d compared to 146 g/m 2 /d in columns operated at neutral pH. No oxidation activity was observed for columns operated at pH 2.5, and DNA sequencing analysis of samples led to the conclusion that highly acidic conditions were responsible for inhibiting the ability of methanotrophs to oxidize CH 4 . Biofilter columns operated at pH 2.5 contained only 2% methanotrophs (type I) out of the total microbial population, compared to 55% in columns operated at pH 7.5. Overall, changes in the population of methanotrophs with acidification within the biofilters compromised its capacity to oxidize CH 4 which demonstrated that a compost biofilter could not operate efficiently in the presence of high levels of H 2 S.

In order to improve the biological oxidation and phosphorous removal in BAF, compound inoculation method was introduced to start two stage biological filters by alternative aeration. The two stage biological filters were connected by serial way, and three phases "batch aeration phase, the phase of small flow water for gradually increasing in the load, the alternative aeration phase" were adopted as the start up procedure. The experimental results showed that: COD removal rate was 83.3% after the former two stages; Ammonia nitrogen removal rate was stable at 81.5% while the TP removal efficiency was 68.9% and COD removal rate reached above 80% at the end of the third phase. Totally, 25 days were necessary for the biofilm formation in two stages BAF.

The presence of arsenic in groundwater comprises a worldwide problem and is recognized as a human health threat. The present work summarizes the arsenic contamination in Europe, where many countries are affected by elevated arsenic concentrations (i.e. Greece, Hungary, Romania, Croatia, Serbia, Turkey, and Spain). In particular, in Greece, several groundwater resources contain arsenic at increased concentrations, which render these water sources as non-potable. Arsenic-affected regions in Greece are classified mainly in three categories, namely, the geothermal-affected waters, the alluvial deposits of rivers and aquifers, and those influenced by mineralization and are typically close to mining activities. In Greece, arsenic concentrations in geothermal waters vary from 30 to 4,500 μg/L, in the regions close to alluvial deposits from 15 to 100 μg/L and in areas affected by mining activities from 20 to 60 μg/L. Arsenic-removal plants have been installed in several towns in Greece. The applied removal technologies are mainly based on chemical precipitation with FeClSO4 or adsorption onto iron oxide materials, such as Bayoxide, granular ferric hydroxide or AquAsZero. In the cases where As(III) is present, biological oxidation or ozonation is applied to convert As(III) to the less mobile forms of As(V). Specific arsenic removal capacity at an equilibrium concentration equal to the regulation limit of 10 μg/L was between 1.7 and 4.2 mg As/g of adsorbent for adsorption processes and between 18 and 59 mg As/g Fe for chemical precipitation.

Methane (CH4) is a potent greenhouse gas often emitted in low concentrations from waste sector activities. Biological oxidation techniques have the potential to offer effective methods for the remediation of such emissions. In this paper, methods of improving the CH4 oxidation performance of a horizontal flow biofilm reactor (HFBR) technology, operated at low temperatures, are investigated.Three pilot scale HFBRs were operated over three studies (Study 1,2 & 3) lasting 310 days in total. The reactors were loaded with 13.2 g CH4/m(3)/h during each study and operated at an average temperature of 10 degrees C.In Study 1, nutrients were added to the biofilm via a liquid nutrient feed (LNF) comprising water and nutrient mineral salts. Average removals were 4.2, 3.1 and 2.3 g CH4/m(3)/h for HFBRs 1, 2 and 3 respectively.In Study 2 silicone oil was added to the LNF of all three HFBRs. Average removals increased, when compared to Study 1, by 31%, 79% and 78% for HFBRs 1, 2 and 3 respectively.In Study 3 a non ionic surfactant (Brij 35) was added to the LNF and silicone oil liquid phase of HFBRs 1 and 2. The operating conditions of HFBR 3 were not changed and it was used as a control. A concentration of 1.0 g Brij 35/L proved most effective in improving reactor performance; with removal rates increasing by 105% and 171% for HFBRs 1 and 2 respectively when compared to Study 1.These results indicate the potential of liquid phase optimisation for improving mass transfer rates and removal performances in biological reactors treating CH4. (C) 2014 Elsevier B.V. All rights reserved. The authors would like to gratefully acknowledge financial support from Science Foundation Ireland (SFI) and Enterprise Ireland. peer-reviewed

The occurrence of discoloured water at the customers’ tap is a great worry for water companies throughout the world. Customers’ express their dissatisfaction when their tap water discolour. This greatly undermines their confidence in water companies. This discolouration is mainly caused by increased levels of Fe and Mn accumulation. This paper presents analysis of a six-year dataset comprising of 36 water quality parameters and customer complaints data covering 176 different district metered areas (DMAs) to identify relevant parameters that influence Iron (Fe) and Manganese (Mn) accumulation potential. Customer complaints data were also investigated for seasonal trends. From the analysis of the data, it was observed that of the 36 parameters only few parameters such as those related to bio-chemical oxidation and sorption significantly influenced the accumulation of Fe and Mn. Majority of the DMAs showed significantly high peaks of customer complaints during summer. These spikes may be attributed to increased water consumption and warmer water temperatures during this period.

A two-stage bioreactor system using sulfur-oxidizing bacteria was studied to abate high strength hydrogen sulfide () from biogas. The two-stage bioreactor consisted of a absorption column (0.5 L) and a microbial oxidation column (1 L) in series, and the liquid medium was continuously recirculated through the columns. The objectives of this study were to determine the feasibility of the bioreactor for biogas desulfurization and to investigate the effect of the medium circulation rate on the system performance. An averaged concentration of introduced to the bioreactor was 530 ppm, corresponding to an overall loading rate of . During the initial 20 days period at the medium recirculation rate of 8 reactor volumes per hour (12 L/hr), the dissolved oxygen (DO) concentration in the oxidation column was 6 mg/L, while the DO in the absorption column was 0.5 mg/L showing that the oxygen contents of the biogas stream was not altered. Because of the biological oxidation of in the oxidation column, the sulfate concentration increased from 200 mg/L to 5,600 mg/L in the liquid medium. The removal efficiency of was greater than 99% in the initial operation period. After the initial period, the medium recirculation rate between the two columns was stepwise changed eight times from 1.0 to 40 vol/hr (1.5~60 L/hr). At the recirculation rate of faster than 4 vol/hr, the removal efficiencies were found to be high, but the efficiency declined at the lower recirculation rates than the threshold.

Biological oxidation of arsenite (As(III)) in synthetic groundwater was examined by using arsenite oxidising bacteria (AOB) isolated from an activated sludge. The phylogenetic analysis indicated that the isolated AOB was closely related to Ensifer adhaerens. Batch experiments showed that for an As(III) oxidation with the isolated AOB the optimum ratio of nitrogen source (NH₄-N) concentration to As(III) concentration was 0.5 (52 mg/L-110 mg/L) and the isolated AOB preferred pH values ranging from 6 to 8, and water temperatures greater than 20 °C. Further continuous experiments were conducted using a bioreactor with immobilised AOB. With an initial As(III) concentration of 1 mg/L at a hydraulic retention time (HRT) of 1 h, an As(III) oxidation rate was around 1 × 10⁻⁹ μg/cell/min and an As(III) oxidation efficiency of 92% was achieved. Although the maximum oxidation rate measured at an HRT of 0.5 h was 2.1 × 10⁻⁹ μg/cell/min, the oxidation efficiency decreased to 87%. These results advocate that a biological process involving immobilised AOB may be useful as an economical and environmentally friendly pre-treatment step for As removal from groundwater.

To understand wastewater quality transformations in the sewer system, a full-scale study focused on the characteristics of the influent wastewater in a middle-sized wastewater-treatment plant receiving only municipal sewage. The objective was to identify conditions in which prefermentation prior to the biological nutrient removal (BNR) process would be useful. Prefermentation aims at increasing the fraction of readily biodegradable organic matter in the wastewater. A correlation between weather conditions and the presence of readily biodegradable organic matter in the feed wastewater was found, but contrary to the expectations, wet weather periods deteriorated the quality of the feed water more than the cold period. Moreover, influent load showed seasonal variation which changes in discharged wastewater could not explain. During the warm water period, significant biological oxidation and nitrogen removal took place in the sewer system, but the plant influent water contained readily biodegradable organic m...

By using parallel process of photocatalysis-biological contact oxidation, a research on the pretreatment effect of micro-polluted raw water was conducted. The result indicates that the changes of HRT and the initial concentration take significant impact on the removal of NH3-N. 60min is the best residence time for the pretreatment. Once the thickness of composite media is 120mm, the removal efficiency of CODMn may reach as much as 15.55%, while the average removal efficiency of turbidity is 20%. Since the nitration reaction consumes certain amount of alkalinity, the pH value of outlet water is lower than inlet water. When employing parallel process, biological oxidation and photocatalysis are performed and finished in the same reactor simultaneously, conducing to maintaining a moderate level of the removal of CODMn and NH3-N. All these are of reference value for its application in practical engineering projects.

Biological Aerated Filter (BAF) has been global applied in secondary and tertiary wastewater treatment process in the past decades. As the increasing application of BAF, it was required to get deeper understanding of the operational discipline, parameter optimization and structural characteristics of BAF to improve the treatment efficiency and to operate stability constantly. In this paper, a physical filtration equation of clean filter bed was established firstly based on an average porosity ratio equation and Kozeny-Carman filtration equation. And then the influence of biological oxidation and biofilm development were introduced, of which the Eckenfelder mode and oxygen transfer were considered, to induce a hybrid physical- biologically equation to describe the headloss development in the BAF.

Aged refuse from waste landfills closed for eight years was examined and found to contain rich methanotrophs capable of biooxidation for methane. Specially, community structure and methane oxidation capability of methanotrophs in the aged refuse were studied. The amount of methanotrophs ranged 61.97 × 10 3 −632.91 × 10 3 cells/g (in dry basis) in aged refuse from Shanghai Laogang Landfill. Type I and II methanotrophs were found in the aged refuse in the presence of sterilized sewage sludge and only Type I methanotrophs were detected in the presence of nitrate minimal salt medium (NMS). The clone sequences of the pmoA gene obtained from the aged refuse were similar to the pmoA gene of Methylobacter, Methylocaldum , and Methylocystis, and two clones were distinct with known genera of Type I methanotrophs according to phylogenetic analysis. Aged refuse enriched with NMS was used for methane biological oxidation and over 93% conversions were obtained.

Formation of disinfection by-products (DBPs) can be controlled by removal of disinfection by-product precursors before disinfection. Variable success has been reported, depending on the treatment used and water tested. Chemical and biological oxidations are candidate technologies to control DBP formation. Given the uncertainty over the identity of DBP precursors, the use of surrogates of natural organic matter (NOM) allows fundamental probing of the links between compound character, removal and DBP formation. Nine compounds were chosen to represent NOM and their removal by two advanced oxidation processes (AOPs), UV-C irradiation and biological treatment compared while haloacetic acid (HAA) formation before and after treatment was measured. Although AOPs were able to fully remove all compounds, incomplete mineralisation led to increased HAA levels, dramatically in the case of two amino acids. Biological treatment was effective in removing amino acids but also moderately increased the HAA formation potential (HAAFP) of hydrophilic compounds. These findings indicate waters with high amino acid concentrations will be susceptible to raised HAA levels following AOP treatment and careful process selection for HAA control is required in such cases.

Hydrogen Sulfide (H2S) is an odourous, highly toxic gas commonly encountered in various commercial and municipal sectors. Three novel, laboratory-scale, Horizontal-Flow Biofilm Reactors (HFBRs) were tested for the removal of H2S gas from air streams over a 178-day trial at 10 degrees C. Removal rates of up to 15.1 g [H2S] m(-3) h(-1) were achieved, demonstrating the HFBRs as a feasible technology for the treatment of H2S-contaminated airstreams at low temperatures. Bio-oxidation of H2S in the reactors led to the production of H+ and sulfate (SO42-) ions, resulting in the acidification of the liquid phase. Reduced removal efficiency was observed at loading rates of 15.1 g [H2S] m(-3) h(-1). NaHCO3 addition to the liquid nutrient feed (synthetic wastewater (SWW)) resulted in improved H2S removal. Bacterial diversity, which was investigated by sequencing and fingerprinting 16S rRNA genes, was low, likely due to the harsh conditions prevailing in the systems. The HFBRs were dominated by two species from the genus Acidithiobacillus and Thiobacillus. Nonetheless, there were significant differences in microbial community structure between distinct HFBR zones due to the influence of alkalinity, pH and SO4 concentrations. Despite the low temperature, this study indicates HFBRs have an excellent potential to biologically treat H2S-contaminated airstreams. This work was supported by Science Foundation Ireland [grant number 08/RFP/ENM1762] and a European Research Council Starting Grant (3C-BIOTECH; no. 261330). peer-reviewed

Water resources in Chinese rural areas were becoming precious because of the polluted water environment. In this paper, the status of rural areas in China has been reviewed. The typical pollutants in rural raw water bodies were different from urban raw water bodies. In rural water environment, organic matters and ammonia nitrogen concentration were high, heavy metal and other toxic pollutants were low. Enhanced coagulation, enhanced filtration, adsorption, biological oxidation and membranes were the main treating methods. The biological oxidation and membranes technology combination was prospected in future rural slightly polluted raw water treatment.

Irradiation with ultrasound (US) and use of an enzyme (E) as pretreatment techniques were carried out to treat a complex effluent (distillery wastewater). These two techniques have been used alone as well as in combination and the efficacy of these techniques was tested by subjecting the effluent to subsequent aerobic biological oxidation (AO). When used alone, US exposure for 30 min and 2 h yielded the best COD reduction during the aerobic oxidation step (US+AO). For the enzyme when used alone, a pH value of 4.8 (corresponding to the optimum pH of the enzyme), a dose of 50 U and a pretreatment time of 24 h yielded better COD removal efficiency as compared to untreated effluent (aerobic oxidation alone). When used in combination, ultrasound followed by enzymatic pretreatment (US+E+AO) yielded the best COD removal efficiencies during aerobic oxidation as compared to the other combinations tested for the treatment of the distillery wastewater. A 4-fold increase in the initial oxidation rate was observed over the untreated batch for the integrated technique (US+E+AO). On the basis of the variation in the values of the biokinetic parameters it can be concluded that the type of pretreatment scheme affects the subsequent rate of the aerobic oxidation significantly.

Optimization of UV/H 2 O 2 process for integration with biological waste treatment unit was done by Taguchi's orthogonal design. Four factors were considered for optimization: Dosage of H 2 O 2 , pH, circulation rate and number of doses of oxidant. For each of the four factors, experiments were run at four levels. For reduction in TOC, single dosage of hydrogen peroxide was observed to be more effective than dosing the same quantity in 2, 4 or 6 equal parts. The effect of circulation rate was found to be insignificant. If AOP were to be designed as a pretreatment step before biological oxidation, 1 mole H 2 O 2 /mole TOC is the optimum level of dosage. This level of addition increased biodegradability. If AOP were to be designed as a post-treatment step after biological oxidation, then 4 mole H 2 O 2 /mole TOC would be the optimum level of dosage. At this level, decrease in TOC was high. Higher pH of the waste liquor generally favoured reduction in TOC.

Iron is generally removed from groundwater by the process of aeration or chemical oxidation followed by rapid sand filtration. Different mechanisms (physicochemical and biological) may contribute to iron removal in filters but the dominant mechanism depends on the physical and chemical characteristics of the water and process conditions applied. Nowadays, there are increasing numbers of publications on methods of biological iron removal which are reported to be much more efficient and cost effective than conventional physicochemical iron removal. However, the biological iron removal mechanism is not fully understood and there are still controversies about whether the mechanism of iron removal in filters could be solely biological or whether the presence of iron oxidising bacteria supplements the physicochemical iron removal mechanisms under certain specific conditions. This paper reviews the theoretical background of biologically mediated iron removal, the process conditions required, the advantages and limitations of the method and a few case studies. A literature review revealed that biological iron removal is not suitable when pH and oxygen concentrations are high and/or NH 4 + , H 2 S and Zn are present. Physicochemical removal mechanisms can achieve the same removal efficiency under the conditions that are reported to be favourable for biological iron removal. Biological iron removal is likely to be supplementary to conventional physicochemical iron removal.

The kinetics of aerobic biological oxidation of a PTA (terephthalic acid) plant waste was investigated for plant effluent (initial COD: 7000–8000 ppm) and anaerobically treated plant effluent (initial COD: 1500–2500 ppm). Experiments were performed at three different Dissolved oxygen (DO) levels viz . low (0.05–0.1 ppm), intermediate (1.00–3.00 ppm) and high (>6.00 ppm). For each DO level at least three mixed liquor suspended solids (MLSS) loadings were studied in the range of 2000–10 000 ppm. Care was taken to eliminate mass transfer resistance for oxygen transfer at gas–liquid and liquid–solid interfaces. An attempt has been made to propose the kinetics of reaction. In order to confirm the rate equation, experiments were also performed in continuous mode of operation over a wide range of MLSS and dissolved oxygen level. A comparison between batch and continuous mode results has been presented.

The passive treatment system designed to treat the mine water discharge of the abandoned Wheal Jane tin mine in Cornwall consisted of a sequence of artificial wetland cells, an anaerobic cell and a final series of rock filters. Three systems were operated which differed only in the pre-treatment of the mine water before discharge to the aerobic wetland cells. The aerobic cells were designed to promote aerobic oxidation and precipitation of iron which could exceed a concentration of 100 mg/l in the raw mine water discharge. The largest investment of land area was to the artificial wetland cells and it was important to understand the processes of oxidation and precipitation of iron so that the performance of this aspect the pilot passive treatment plant (PPTP) could be managed as efficiently as possible. The generally low pH of the influent mine water and inevitable trend of decreasing pH due to hydrolysis of Fe(III) meant that distinguishing between biotic and abiotic mechanisms was fundamental for further design planning of passive treatment systems. This paper describes these observations.

Oxidation of ferrous (Fe2+) ion to ferric (Fe3+) ion under acidic conditions can be achieved by iron oxidizing bacteria. In this research study, oxidation of Fe2+ ions by iron oxidizing bacteria was studied using a bench-scale rotating biological contactor (RBC). Experiments were conducted to investigate the effects of parameters such as hydraulic loading rate (HLR), temperature and Fe2+ concentration at pH 2.0 on Fe2+ oxidation. Oxidation of Fe2+ was observed to decrease with temperature (in the range of 5 to 23 °C). The Fe2+ oxidation rates of 35.3 g Fe2+/(m2·d) and 52.6 g Fe2+/(m2·d) were observed at 5 °C and 21 °C, respectively, at HLR of 0.014 m3/(m2·d). The Fe2+ oxidation rates increased with increase in HLR from 0.014 m3/(m2·d) to 0.055 m3/(m2·d) for a Fe2+ concentration of approximately 3200 mg/L in the RBC feed. The maximum Fe2+ oxidation rate observed in this study was 165 g Fe2+/(m2·d). Iron solids were deposited on the RBC disks and were identified as jarosite. The RBC was able to achieve 50% Fe2+ oxidation efficiency after 24 h of a process upset. Key words: rotating biological contactor, ferrous, ferric, oxidation, acidic mine drainage, hydraulic retention time, hydraulic loading rate.

Ozonation of industrial and sewage sludge is a suitable process for minimizing the sludge production of activated sludge processes. The ozonation has the advantage for complete oxidation of volatile suspended solids (VSS) of combining partial sludge oxidation with subsequent biological oxidation. This paper describes the evaluation of two full-scale sewage sludge ozonation investigations for subsequent aerobic stabilisation as well as for subsequent anaerobic stabilisation compared to different sludge treatment processes. For both the anaerobic and aerobic application, sludge liquefying by release of 110 and 160 mg COD per g total suspended solids (TSS) has been reached at specific ozone consumption of 0.03 and 0.06 kg O3 per kg TSS, respectively. The subsequent biological treatment has reached a mass reduction of 20-35% for the aerobic and 19% for the anaerobic stabilisation. For both applications the specific ozone consumption was about 0.05 kg O3 per kg TSS to be treated. A comparison with mechanical and thermo-chemical sludge mass reduction methods shows that the mass reduction potential of ozonation is presently higher. Even though costs for sludge ozonation are higher compared to other methods, the optimisation potential for cost reduction of sludge ozonation is obvious from the results presented in this paper.

In this article, all relevant biological oxidation processes for the treatment of wastewaters, based on both suspended and attached cultures, have been treated. Moreover, biological processes for the natural treatment (such as lagoons and constructed wetlands) have been taken into account. Particularly, an overview of the various processes, traditional and innovative, is offered by both citing a summary of their main features and highlighting all technological and process advances currently available in the literature.

An analysis is made of the literature on the mechanism of biosorption-bioregeneration of organic substances mainly on activated carbon (AC). There have advanced two hypotheses on the biosorption mechanism: the Rodman exoenzymatic hypothesis and the bioregeneration approach of Andrews and Chi Tien. In addition, it was shown that the principal mechanism responsible for the removal of both biodegradable and bioresistant compounds is biological oxidation, but only in combination with adsorption on activated carbon. The authors examine the role of the filter medium in biosorption, factors affecting efficiency of biosorption and bioregeneration of AC and technological aspects of the application of biosorptive processes.

The aim of our work was to evaluate the effects of NaOH addition to aerated mine lake sediment on the production of sulphate and to discriminate between the spontaneous chemical oxidation and microbially mediated oxidation of sulphurous compounds. From the viewpoint of practical applicability, we asked ourselves the following key questions: (1) does NaOH addition control the chemical and biological oxidation of sulphate in aerated sediment? and (2) can NaOH be used in practice to control sulphate production? From our experimental results, we can conclude that (1) NaOH amendment controls the rate of both chemical (enhancement) and biological (suppression) processes and (2) NaOH amendment under practical conditions can not be applied to reduce the total amount of produced sulphate from aerated sediment.

Experimental examples of sequential chemical and biological oxidation treatment have been previously reviewed by Scott and Ollis, and economic estimates proposed by Esplugas and Ollis. Despite the prevalence of examples evident in these reviews and in recent conferences, very little use of kinetic models to codify and rationalize results on complex or simulated wastewaters has appeared. In consequence, models are not widely available nor have they yet received widespread acceptance as a method of analysis and reporting. To ameliorate this situation we here report a summary of important kinetic behaviors characteristic of individual chemical and biological kinetics, and provide experimental examples from recent works which illustrate the utility of such simple kinetic forms to construct two step treatment engineering models for complex wastewater and waters.

The combined TiO 2 -assisted photocatalytic reduction of TNT in series with fungal mineralization by Phanerochaete chrysosporium was investigated. Previously unreported byproducts from the photocatalytic reduction of TNT (at pH 3.1 to 6.6 under a nitrogen atmosphere) were observed: 4-amino-2,6-dinitrotoluene, 2,4-diamino-6-nitrotoluene, 4-hydroxylamino-2,6-dinitrotoluene, 2,4-dihydroxylamino-6-nitrotoluene, and 2-hydroxylamino-4-amino-6-nitrotoluene. The extent of TNT mineralization was approximately 14% by biological transformation alone and improved to approximately 32% using the combined photocatalytic and fungal treatment. No significant mineralization was seen during photocatalytic reduction of TNT. Six hours of photocatalytic pretreatment resulted in the greatest extent of biological mineralization in the combined process. In addition, solubility and polarity of transformation products was increased in the combined treatment over that of fungal or photocatalytic transformation alone. HPLC, mass spectrometry and 14 C-radiotracer analyses of the TNT transformations were conducted to show both qualitative and quantitative aspects of the photocatalytic reduction and biological oxidation sequences. This experimentation demonstrated that a combined photochemical and biological sequence of treatment may be a viable method of treating aqueous TNT wastes.

Large-scale ozone generation for municipal and industrial purposes has been entirely based on the creation of microplasmas or microdischarges which are a type of non-thermal or cold plasma created using a reactor known as a dielectric barrier discharge (DBD). Even though microplasma generated ozone has been in continuous use for over a hundred years especially in water treatment, recent shifts in environmental awareness and sustainability have lead to a surge of ozone generating facilities throughout the world. Along with the global expansion of this environmental cleaning application various new discoveries have emerged in the science and technology of ozone generation. This chapter will briefly describe some of the historical and recent developments of this plasma application. A more comprehensive overview of the discharge physics, plasma chemistry, and the biological oxidation capabilities of ozone will be addressed along with a review of some of the most recent breakthrough developments and challenges in large-scale ozone generation technology.

A trickling filter for iron removal from potable water has been constructed and tested. Iron removal was found to be caused by both biological and physico-chemical iron oxidation. The extent of each oxidation type was assessed. In addition, iron concentration profiles were taken along the filter depth, for both biological and physico-chemical iron oxidation, under the same operating conditions. Significant quantities of iron precipitated, mandating a periodic filter backwash. The possible duration of the filter operating cycles was studied as a function of the inlet iron concentration and the volumetric flow-rate. The limits of feed iron concentration and hydraulic loadings on the filter were determined and appropriate operating diagrams were constructed.

Semicontinuous activated-sludge (SCAS) units inoculated with activated sludge from a plant treating predominantly domestic wastewater were used to study EDTA removal from wastewater at different pH values. Almost complete removal of EDTA was found in units maintained at pH > 8·0, but high EDTA removal was obtained only in SCAS units run with sludge retention times ≥ 12 days. A maximum EDTA removal rate of 0·2 kg EDTA/m 3 /day was achieved in the SCAS units. A full-scale activated-sludge system operating under alkaline conditions provided high removal percentages, confirming the removal of EDTA in activated-sludge systems as established in the SCAS tests. The results in both laboratory and full-scale activated-sludge units showed that a reduction of more than 90% of the incoming EDTA was attainable. Ratios of biological oxygen demand to theoretical oxygen demand of > 0·6 in closed-bottle tests, inoculated with either sludge from a full-scale treatment plant or an SCAS unit, proved that EDTA was removed by biodegradation. These results clearly demonstrated that EDTA-containing wastewater is amenable to activated-sludge treatment in conventional plants operated under alkaline conditions.

There are growing concerns about the increasing trends of emerging micropollutants in the environment due to their potential negative impacts on natural ecosystems and humans. This has attracted attention from both governmental and non-governmental organisations worldwide. Pharmaceuticals, personal care products, and endocrine disruptors are continuously being released consciously or unconsciously into water sources due to poor regulatory frameworks especially in the developing countries. The effects of these contaminants are poorly known. They are not easily biodegradable and have become an environmental nuisance and public health issue. This has heightened the risk of exposure to their deleterious effects in such countries where the majority of the population are still struggling to have access to good quality drinking water supplies and better sanitation. With the rising fear of short- and long-term impacts of the ever-increasing number of persistent recalcitrant organic compounds accumulating in the environment, their removal is gradually becoming an issue to the water treatment industry. Hence, there is a need to develop functional techniques for the management of water contaminated by these emerging contaminants so as to increase the availability and access to safe and good-quality drinking water. We conducted a narrative review on these emerging micropollutants and examined their various documented sources, effects, as well as recent techniques for their effective removal. This becomes necessary due to the increasing occurrence of these pollutants in the aquatic and terrestrial environment. These levels are expected to further increase in the coming years as a consequence of the ever-increasing population density which undoubtedly characterizes developing economies. Our findings show that the present reported treatment techniques in the literature such as biological oxidation/biodegradation, coagulation/flocculation, ozonation, electrodialysis, reverse osmosis, sedimentation, filtration, and activated carbon were not designed for removal of these newly identified contaminants, and as such, the techniques are not sufficient and unable to completely degrade the compounds. We therefore recommended the need for concerted efforts to develop better techniques, especially combined advanced oxidative methods to address the shortcomings of and growing challenge to current practices.

The oxygen balance in wastewater collection systems is important in respect to the degree of biological oxidation that occurs within the stream and in respect to the control of septicity and its effects. In this paper, a simple mathematical model is presented, in order to predict dissolved oxygen concentration profiles along sanitary sewers. The mathematical model was developed based on an analytical solution of the simple differential equation of dissolved oxygen balance in sewers, and includes an empirical expression for prediction of dissolved oxygen transfer to the slime layer on the pipe walls. Because the factors controlling dissolved oxygen balance in sewers are so complex, it would be unrealistic to expect, that with this rather simple model, dissolved oxygen concentrations can be accurately predicted. Nevertheless, it is reasonable to suppose that the predictions may be adequate for some design and operation purposes.

Chlorendic acid, a fire retardant, was subjected to sequential chemical/biological oxidation. Degradation of chlorendic acid was achieved by ozonation with chlorinated and non-chlorinated by-product production. The destruction of chlorendic acid and by-product distribution was a function of ozone contact time. After 450 min of ozonation, chlorendic acid and TOC removal percentages equaled 98% and 62.5%, respectively. When subject to 210 min of UV oxidation, chlorendic acid and TOC removal equaled 70 and 31%, respectively. With combined ozone/UV, near complete removal of chlorendic acid and TOC was achieved in 90 and 120 min, respectively. In biodegradation testing, chlorendic acid was not degradable. Biodegradation efficiency (DOC removal) of chlorendic acid ozonation by-products was a function of ozone contact time and approached 80%. Chlorendic acid UV oxidation products (210 min contact time) were poorly biodegraded. Ozone/UV oxidation products (40 min contact time) from chlorendic acid achieved 89% biodegradation. Biodegradation rates of chlorendic acid chemical oxidation by-products also were assessed. Based on the computed biokinetic values of biodegradation rates for the chemical oxidation products of chlorendic acid are sufficiently high to enable use of existing biological process infrastructure for treatment of chemical oxidation products.

This study aimed at the identification of microorganisms present in the scum layer of the settler compartment of upflow anaerobic sludge blanket (UASB) reactors, and to evaluate their role in the biological oxidation of sulphides. The experiments were conducted using scum samples taken from two pilot-scale UASB reactors, both treating domestic wastewater. Microorganisms similar to Beggiatoa sp., Thiotrix sp. and species of cyanobacteria were identified based on their morphology, and most of them have been shown to be capable of carrying out sulphur oxidation. Tests of biological oxidation of sulphides using scum and cultures of the cyanobacteria Phormidium and Pseudoanabaena showed a significant decrease in the concentrations of the sulphides, suggesting that the microorganisms present in the scum layer can play a role in the minimization of odour emissions.

As the incidence of respiratory and allergic symptoms has been reported to be increased in children attending schools in close proximity to busy roads, it was hypothesised that PM from roadside schools would display enhanced oxidative potential (OP). Two consecutive one-week air quality monitoring campaigns were conducted at seven school sampling sites, reflecting roadside and urban background in London. Chemical characteristics of size fractionated particulate matter (PM) samples were related to the capacity to drive biological oxidation reactions in a synthetic respiratory tract lining fluid. Contrary to hypothesised contrasts in particulate OP between school site types, no robust size-fractionated differences in OP were identified due high temporal variability in concentrations of PM components over the one-week sampling campaigns. For OP assessed both by ascorbate (OP(AA) m(-3)) and glutathione (OP(GSH) m(-3)) depletion, the highest OP per cubic metre of air was in the largest size fraction, PM(1.9-10.2). However, when expressed per unit mass of particles OP(AA) µg(-1) showed no significant dependence upon particle size, while OP(GSH) µg(-1) had a tendency to increase with increasing particle size, paralleling increased concentrations of Fe, Ba and Cu. The two OP metrics were not significantly correlated with one another, suggesting that the glutathione and ascorbate depletion assays respond to different components of the particles. Ascorbate depletion per unit mass did not show the same dependence as for GSH and it is possible that other trace metals (Zn, Ni, V) or organic components which are enriched in the finer particle fractions, or the greater surface area of smaller particles, counter-balance the redox activity of Fe, Ba and Cu in the coarse particles. Further work with longer-term sampling and a larger suite of analytes is advised in order to better elucidate the determinants of oxidative potential, and to fuller explore the contrasts between site types.

An experimental bio-column composed of aged refuse was installed around the exhaust pipe as a new way to mitigate methane in refuse landfill. One of the objectives of this work was to assess the effect of aged refuse thickness in bio-column on reducing CH 4 emissions. Over the study period, methane oxidation was observed at various thicknesses, 5 cm (small size), 10 cm (middle size) and 15 cm (large size), representing one to three times of pipeline diameters. The middle and large size both showed over 90% methane conversion, and the highest methane conversion rate of above 95% occurred in the middle-size column cell. Michaelis-Menten equation addressed the methanotrophs diffusion in different layers of the bio-columns. Maximum methanotrophic activity ( V max ) measured at the three thicknesses ranged from 6.4 × 10 −3 to 15.6 × 10 3 units, and the half-saturation value ( K M ) ranged from 0.85% to 1.67%. Both the highest V max and K M were observed at the middle-size of the bio-column, as well as the largest methanotrophs population, suggesting a significant efficiency of methane mitigation happened in the optimum zone with greatest affinity and methanotrophic bacteria activities. Therefore, bio-column is a potential style for methane abatement in landfill, and the aged refuse both naturally formed and artificially placed in the column plays a critical role in CH 4 emission.

In order to optimise methane oxidation in landfill cover soils, it is important to be able to accurately quantify the amount of methane oxidised. This research considers the gas push-pull test (GPPT) as a possible method to quantify oxidation rates in situ. During a GPPT, a gas mixture consisting of one or more reactive gases (e.g., CH(4), O(2)) and one or more conservative tracers (e.g., argon), is injected into the soil. Following this, the mixture of injected gas and soil air is extracted from the same location and periodically sampled. The kinetic parameters for the biological oxidation taking place in the soil can be derived from the differences in the breakthrough curves. The original method of Urmann et al. (2005) was optimised for application in landfill cover soils and modified to reduce the analytical effort required. Optimised parameters included the flow rate during the injection phase and the duration of the experiment. 50 GPPTs have been conducted at different landfills in Germany during different seasons. Generally, methane oxidation rates ranged between 0 and 150 g m(soil air)(-3)h(-1). At one location, rates up to 440 g m(soil air)(-3)h(-1) were measured under particularly favourable conditions. The method is simple in operation and does not require expensive equipment besides standard laboratory gas chromatographs.

Characteristics of degradation of cyanobacteria, Microcystis aeruginosa, by Masugophota-Monas guttula were examined. Monoxenic M.guttula was isolated from sewage in the biological oxidation facility equipped in Kasumigaura Water Works. M.guttula was able to efficiently degrade viable cells of M.aeruginosain a short time. The removal of cells by M.guttula was 90% at 48 hr cultivation. The specific growth rate (µ) and generation time (tg) of M.guftuia were 4. l day−1 and 4.0 hr, respectively. The maximum specific growth rate(µmax) and saturation coefficient (Ks) of the microbe were 4.4day−1 and 2.4 mg/l with Lineweaver-Burke equation. Effects of physical factors on the removal of M.aeruginosa by M.guttula, pH and temperature were examined. Greater than 80% of removal was obtained at pH 7.0. At 30°C, the maximum removal was over 90% as compared with 20% at 5°C. It was clarified that M.guttula could effectively utilize M.aeruginosa as food, and it was found that pH and temperature were important physical factors to remove the Cyanobacterium M. aeruginosaby microflagellate M.guttula.