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In this study, an anaerobic baffled reactor (ABR) with four compartments was employed to treat alkalidecrement wastewater of polyester fabrics under different organic loading rates. The stable operation of this reactor was achieved in 70 days at a hydraulic retention time of 36 h and mesophilic temperature of 35°1 °C. It is found that the chemical oxygen demand removal and decolorization of this system can be as high as 79.0% and 87.7%, respectively. The different acidogenesis and methanogenesis in four compartmentswas acclimated by the variation of pH, oxidation reduction potential values and operational conditions in the spatial distribution of the first to fourth compartments of the ABR system. In addition, the dehydrogenase activity (DHA) and coenzyme F420 concentrations along the four compartments ranged from 67.8 to 185.21 μgTF/(gVSS·h) (TF: triphenyl formazan; VSS: volatile suspended solids) and 0.123 to 0.411 μmol/g, respectively. These results indicated that the ABR could separate acidogenesis and methanogenesis in longitudinal distribution and treat well the alkali-decrement wastewater. [ABSTRACT FROM AUTHOR]

The phosphoric acid production obtained by attacking phosphate rock by sulphuric acid cogenerates considerable quantities of phosphogypsum. The world cogeneration is estimated about 100-280 Mt per year. In another context of sustainable development, the phosphate chemical industry develops different ways of phosphogypsumvalorization,whichmakes its storage stack in a suitableway for its potential use as an industrial by-product. Although, this storage can cause an environmental impact largely due to the transfer of trace elements (TEs) to groundwater by leaching. It is therefore important to evaluate the impact linked to the storage in order to limit this transfer. The evaluation is usually performed through leaching tests in columns or reactor. In this work, leaching tests were performed in columns by infiltration-percolation on two filter mediums: phosphogypsum and synthetic sandy soils. The results showed that the phosphogypsum is acting as a filter, which retains and releases the TEs. Most of these TEs (Pb, Se, Ag, Zn and Cu) were highly retained in the synthetic soils surfaces and their contents in waters were considerably lower than the maximum contaminant levels (MCLs). Although As, Cd, Cr and Ni were strongly transferred to groundwater, their respective contents were higher than the MCLs. [ABSTRACT FROM AUTHOR]

The performance of two bench scale activated sludge reactors with two feeding regimes, continuous fed (an up-flow aerobic/anoxic sludge fixed film (UAASFF) bioreactor) and batch fed (sequencing batch reactor (SBR)) with intermittent aeration, were evaluated for simultaneous nutrients (N, P) removal. Three significant variables (retention/reaction time, chemical oxygen demand (COD): N (nitrogen): P (phosphorus) ratio and aeration time) were selected for modeling, analyzing, and optimizing the process. At high retention time (≥6 h), two bioreactors showed comparable removal efficiencies, but at lower hydraulic retention time, the UAASFF bioreactor showed a better performance with higher nutrient removal efficiency than the SBR. The experimental results indicated that the total Kjeldahl nitrogen removal efficiency in the UAASFF increased from 70.84% to 79.2% when compared to SBR. It was also found that the COD removal efficiencies of both processes were over 87%, and total nitrogen and total phosphorus removal efficiencies were 79.2% and 72.98% in UAASFF, and 71.2% and 68.9% in SBR, respectively. [ABSTRACT FROM AUTHOR]

The accuracy of a biofilm reactor model depends on the extent to which physical system conditions particularly bulk-liquid hydrodynamics and their influence on biofilm dynamics) deviate from the ideal conditions upon which the model is based. It follows that an improved capacity to model a biofilm reactor does not necessarily rely on an improved biofilm model, but does rely on an improved mathematical description of the biofilm reactor and its components. Existing biofilm reactor models typically include a one-dimensional biofilm model, a process (biokinetic and stoichiometric) model, and a continuous flow stirred tank reactor (CFSTR) mass balance that [when organizing CFSTRs in series] creates a pseudo two-dimensional (2-D) model of bulk-liquid hydrodynamics approaching plug flow. In such a biofilm reactor model, the user-defined biofilm area is specified for each CFSTR; thereby, Xcarrier does not exit the boundaries of the CFSTR to which they are assigned or exchange boundaries with other CFSTRs in the series. The error introduced by this pseudo 2-D biofilm reactor modeling approach may adversely affect model results and limit model-user capacity to accurately calibrate a model. This paper presents a new sub-model that describes the migration of Xcarrier and associated biofilms, and evaluates the impact that Xcarrier migration and axial dispersion has on simulated system performance. Relevance of the new biofilm reactor model to engineering situations is discussed by applying it to known biofilm reactor types and operational conditions. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the organic removal efficiency and microbial population dynamics in activated sludge with pressurized aeration. The activated sludge was fed with synthetic wastewater composed of simple carbon source to avoid the effect of complex components on microbial communities. The pressurized acclimation process was conducted in a bench-scale sequencing batch reactor (SBR) under 0.3 MPa gage pressure. Another SBR was running in atmospheric environment as a control reactor, with the same operation parameters except for the pressure. Bacterial diversity was investigated by Illumina sequencing technology. The results showed that the total organic carbon removal efficiency of the pressurized reactor was significantly higher, while the mixed liquor suspended solids concentrations were much lower than those of the control reactor. Moderate pressure of 0.3 MPa had little effect on Alpha-diversity of bacterial communities due to the similar running conditions, e.g., feed water, solids retention time (SRT) and the cyclic change of dissolved oxygen (DO) concentrations. Although the relative percentage of the bacterial community changed among samples, there was no major change of predominant bacterial populations between the pressurized group and the control group. Pressurized aeration would have a far-reaching impact on microbial community in activated sludge when treating wastewaters being unfavorable to the dissolution of oxygen. [ABSTRACT FROM AUTHOR]

Sulphides are present in many wastewater streams; their removal is important due to corrosiveness, toxicity and unpleasant odour, and can be carried out by anaerobic biological treatment. This study focuses on the temperature effect (25-10 °C) on an expanded granular sludge bed (EGSB) reactor for sulphide removal using nitrate as electron acceptor. The reactor was run at a NO3-/HS- molar ratio of 0.35 and pH of 8.5-9.0. Samples were analysed by ion chromatography (NO3-, SO42- and S2O32-), spectrophotometry (S2-) and by scanning electron microscopy (SEM). S2- and NO3- removal was 99.74±0.04 and 99.5±2.9%, respectively. Sulphur (S0) was found on the outer granule surface and struvite inside the granule, by SEM. Sulphide conversion to sulphur was up to 76%. Temperature transitions and levels influenced S2O32- and SO42- concentrations. [ABSTRACT FROM AUTHOR]

Moving bed biofilm reactor (MBBR) system has a successful operation in the treatment of different types of wastewater. Since the media, i.e. the place of growth and formation of biofilm, play the main role in the treatment in this system, MBBR systems were operated in the present research with modified Bee-cell media. Activated carbon granules of almond or walnut shells were placed in media pores to improve the treatment of refinery oil wastewater and their operation with MBBR system was compared with the conventional Bee-cell media. In these experiments, the effects of organic loading rate, hydraulic retention time (HRT), media filling ratio (MFR), and activated carbon concentration (ACC) used in the media were investigated on the operation of MBBR systems. The analysis of results estimated the optimal values of HRT, MFR, and ACC used in the media between the studied levels, being equal to 22 h, 50%, and 7.5 g/L, respectively. Under these conditions, total petroleum hydrocarbons removal efficiencies for MBBR systems using Bee-cell media with carbon of almond, carbon of walnut shells, and a carbon-free system were 95± 1.17%, 91±1.11%, and 57±1.7%, respectively, which confirms the adsorption ability of systems with the media containing activated carbon in the removal of petroleum compounds from wastewater. [ABSTRACT FROM AUTHOR]

A flux-step method was used for monitoring the pressure variation in a solids separation membrane at different operating conditions. A submerged membrane bioreactor pilot plant, used during the short-term tests, was used to purify actual restaurant wastewater. The influence of membrane backwash and relaxation on the variation of pressure variation was also evaluated. In order to reduce the deposition of irreversible fouling, the authors modified the literature-supported filtration to backwash cycling with filtration and relaxation cycling. The trials maintained a constant filtration to relaxation ratio that was in line with optimal filtration to backwashing ratios found in the literature. The relaxation cycling between two constant flux-steps effectively counteracted membrane fouling and the excessive decrease in average pressure, and it results in a lower waste of energy and water than a backwashing strategy. [ABSTRACT FROM AUTHOR]

A new principle for mainstream nitrogen removal through nitritation followed by anammox was studied in a two-stage moving bed biofilm reactor (MBBR) configuration. The first stage was optimized for nitritation by using thin biofilms and a feed alternating between synthetic mainstream wastewater at 15 °C and, for shorter periods, synthetic reject water at 30 °C. The exposure of the biofilm to reject water conditions aimed to improve the growth conditions for ammonia oxidizing bacteria, while inhibiting nitrite oxidizing bacteria. The biofilm thickness was maintained below 200 µm to ensure high exposure of the total biomass to the bulk reactor conditions. Nitritation was successfully achieved in the configuration, with a nitrite accumulation ratio above 75% during the majority of the study, and ammonia removal rates between 0.25 and 0.50 g NH4-N/L,d. The anoxic second stage, optimized for anammox, was fed with the effluent from the nitritation reactor, reaching nitrogen removal rates above 0.20 g TN/L,d. [ABSTRACT FROM AUTHOR]

A simplified fixed biofilm model was developed to formulate the relationship between the substrate concentrations at both the entry and exit, at the biofilm–liquid interface and at the biofilm attached surface along with average substrate flux in the biofilm, substrate flux at the biofilm–liquid interface and effective biofilm thickness. The model considered the substrate mass transport external to the biofilm and into the biofilm as per Fick's law and the steady state substrate as well as biomass balance for attached growth microorganisms. Monod's growth kinetics has been adopted in substrate utilization, incorporating relevant boundary conditions. The numerical solution of model equations was accomplished for calculating average flux and exit substrate concentration and thereafter the Runge–Kutta method was employed for determining effective biofilm thickness. Consequently, two computer programs were developed for the purpose of rapid solution. The model was satisfactorily applied to data available from the literature for checking its accuracy and was validated with the experimental results. The model was found to be an easy, accurate and fast method that can be used for process design of a fixed biofilm reactor. [ABSTRACT FROM AUTHOR]

In a co-digestion system running with rapeseed oil and sewage sludge, an extremely fast increase in the organic loading rate was studied to develop a procedure to allow for flexible and demand-driven energy production. The over-acidification of the digestate was successfully prevented by calcium oxide dosage, which resulted in granule formation. Mineralogical analyses revealed that the granules were composed of insoluble salts of long chain fatty acids and calcium and had a porous structure. Long chain fatty acids and calcium formed the outer cover of granules and offered interfaces on the inside thereby enhancing the growth of biofilms. With granule size and age, the pore size increased and indicated degradation of granular interfaces. A stable biogas production up to the organic loading rate of 10.4 kg volatile solids m–3 d–1 was achieved although the hydrogen concentration was not favorable for propionic acid degradation. However, at higher organic loading rates, unbalanced granule formation and degradation were observed. Obviously, the adaption time for biofilm growth was too short to maintain the balance, thereby resulting in a low methane yield. [ABSTRACT FROM AUTHOR]

This present study aimed to characterize the bacterial community in a well-established nitrifying reactor by high-throughput sequencing of 16S rRNA amplicons. The laboratory-scale continuous stirred tank reactor has been supplied with ammonium (NH4+) as sole energy source for over 5 years, while no organic carbon has been added, assembling thus a unique planktonic community with a mean NH4+ removal rate of 86±1.4 mg NH4+-N/(L d). Results showed a nitrifying community composed of bacteria belonging to Nitrosomonas (relative abundance 11.0%) as the sole ammonia oxidizers (AOB) and Nitrobacter (9.3%) as the sole nitrite oxidizers (NOB). The Alphaproteobacteria (42.3% including Nitrobacter) were the most abundant class within the Proteobacteria (62.8%) followed by the Gammaproteobacteria (9.4%). However, the Betaproteobacteria (excluding AOB) contributed only 0.08%, confirming that Alpha- and Gammaproteobacteria thrived in low-organic-load environments while heterotrophic Betaproteobacteria are not well adapted to these conditions. Bacteroidetes, known to metabolize extracellular polymeric substances produced by nitrifying bacteria and secondary metabolites of the decayed biomass, was the second most abundant phylum (30.8%). It was found that Nitrosomonas and Nitrobacter sustained a broad population of heterotrophs in the reactor dominated by Alpha- and Gammaproteobacteria and Bacteroidetes, in a 1:4 ratio of total nitrifiers to all heterotrophs. [ABSTRACT FROM AUTHOR]

This research was carried out on a full-scale pure oxygen thermophilic plant, operated and monitored throughout a period of 11 years. The plant treats 60,000 t y-1 (year 2013) of high-strength industrial wastewaters deriving mainly from pharmaceuticals and detergents production and landfill leachate. Three different plant configurations were consecutively adopted: (1) biological reactor + final clarifier and sludge recirculation (2002-2005); (2) biological reactor + ultrafiltration: membrane biological reactor (MBR) (2006); and (3) MBR + nanofiltration (since 2007). Progressive plant upgrading yielded a performance improvement chemical oxygen demand (COD) removal efficiency was enhanced by 17% and 12% after the first and second plant modification, respectively. Moreover, COD abatement efficiency exhibited a greater stability, notwithstanding high variability of the influent load. In addition, the following relevant outcomes appeared from the plant monitoring (present configuration): up to 96% removal of nitrate and nitrite, due to denitrification; low-specific biomass production (0.092 kgVSS kgCODremoved-1 ), and biological treatability of residual COD under mesophilic conditions (BOD5/COD ratio = 0.25-0.50), thus showing the complementarity of the two biological processes. [ABSTRACT FROM AUTHOR]

The reduction of biological excess sludge production using ozone is a well-known technology and is applied in several full-scale plants around the world. Nevertheless, optimisation of the process is not yet adequately documented in the literature. Operational parameters are usually chosen by assuming a direct proportionality between ozone dose and excess sludge reduction. This paper investigates the role of ozone concentration on process efficiency and demonstrates the (non-linear) inverse relationship between ozone dose and specific particulate chemical oxygen demand solubilisation in plug-flow contact reactors. The influence of total suspended solids concentration is also studied and described. No short-term lethal effects on heterotrophic biomass have been observed. [ABSTRACT FROM AUTHOR]

In wastewater treatment plants (WWTPs), activated sludge is thickened in secondary settling tanks and recycled into the biological reactor to maintain enough biomass for wastewater treatment. Accurately estimating the activated sludge concentration in the lower portion of the secondary clarifiers is of great importance for evaluating and controlling the sludge recycled ratio, ensuring smooth and efficient operation of the WWTP. By dividing the overall activated sludge-thickening curve into a hindered zone and a compression zone, an empirical model describing activated sludge thickening in the compression zone was obtained by empirical regression. This empirical model was developed through experiments conducted using sludge from five WWTPs, and validated by the measured data from a sixth WWTP, which fit the model well (R2 = 0.98, p <0.001). The model requires application of only one parameter, the sludge volume index (SVI), which is readily incorporated into routine analysis. By combining this model with the conservation of mass equation, an empirical model for compression settling was also developed. Finally, the effects of denitrification and addition of a polymer were also analysed because of their effect on sludge thickening, which can be useful for WWTP operation, e.g., improving wastewater treatment or the proper use of the polymer. [ABSTRACT FROM AUTHOR]

Sludge bulking caused by loss of stability is a major problem in aerobic granular sludge systems. This study investigated the feasibility of preventing sludge bulking and enhancing the stability of aerobic granular sludge in a sequencing batch reactor by optimizing operation conditions. Five operation parameters have been studied with the aim to understand their impact on sludge bulking. Increasing dissolved oxygen (DO) by raising aeration rates contributed to granule stability due to the competition advantage of non-filamentous bacteria and permeation of oxygen at high DO concentration. The ratio of polysaccharides to proteins was observed to increase as the hydraulic shear force increased. When provided with high/low organic loading rate (OLR) alternately, large and fluffy granules disintegrated, while denser round-shape granules formed. An increase of biomass concentration followed a decrease at the beginning, and stability of granules was improved. This indicated that aerobic granular sludge had the resistance of OLR. Synthetic wastewater combined highly and slowly biodegradable substrates, creating a high gradient, which inhibited the growth of filamentous bacteria and prevented granular sludge bulking. A lower chemical oxygen demand/N favored the hydrophobicity of granular sludge, which promoted with granule stability because of the lower diffusion rate of ammonia. The influence of temperature indicated a relatively low temperature was more suitable. [ABSTRACT FROM AUTHOR]

In Japan, membrane bioreactor (MBRs) have been installed in 17 small-scale municipal wastewater treatment plants (WWTPs) in the past 8 years, together with two recently installed MBRs for largerscale WWTPs. In this study, design and operating data were collected from 17 of them as part of a follow-up survey, and aspects including system design, biological treatment, membrane operation, problems and costs were overviewed. Because most of the MBRs were designed according to standardized guidance, system configuration of the plants was similar; pre-denitrification using the Modified Ludzack-Ettinger (MLE) process with membrane units submerged in aerobic tanks, following a fine screen and flow equalization tank. This led to effluent quality with biochemical oxygen demand and T-N of less than 3.5 and 7.4 mg/L, respectively, for nine plants on an annual average basis. It was a common practice in extremely under-loaded plants to operate the membrane systems intermittently. Frequency of recovery cleaning events was plant-specific, mostly ranging from 1 to 5 times/year. Cost evaluation revealed that specific construction costs for the small-scale MBRs were no more than for oxidation ditch plants. Although specific energy consumption values tended to be high in the underloaded plants, the demonstration MBR, where several energy reducing measures had been incorporated, attained specific energy consumption of 0.39 kWh/m3 under full-capacity operation. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) techniques are ideally suited for the study of biofilms and for probing their microenvironments because these techniques allow for noninvasive interrogation and in situ monitoring with high resolution. By combining NMR with simultaneous electrochemical techniques, it is possible to sustain and study live biofilms respiring on electrodes. Here, we describe a biofilm microreactor system, including a reusable and a disposable reactor, that allows for simultaneous electrochemical and NMR techniques (EC-NMR) at the microscale. Microreactors were designed with custom radio frequency resonator coils, which allowed for NMR measurements of biofilms growing on polarized gold electrodes. For an example application of this system we grew Geobacter sulfurreducens biofilms on electrodes. EC-NMR was used to investigate growth medium flow velocities and depth-resolved acetate concentration inside the biofilm. As a novel contribution we used Monte Carlo error analysis to estimate the standard deviations of the acetate concentration measurements. Overall, we found that the disposable EC-NMR microreactor provided a 9.7 times better signal-to-noise ratio over the reusable reactor. The EC-NMR biofilm microreactor system can ultimately be used to correlate extracellular electron transfer rates with metabolic reactions and explore extracellular electron transfer mechanisms. [ABSTRACT FROM AUTHOR]

This work aims to evaluate the efficiency of ammonium removal from piggery wastewater by an intermittent aeration (IA) sequencing batch reactor (SBR) with immobilized NH4+-reducing bacteria under mesophilic conditions. When a 20-L bench-scale SBR with 11% (v/v) of alginate beads containing NH4+-reducing bacteria was used, removal efficiency of NH4+ was 63% after 240 h. When a full-scale SBR system (available volume=83 m3) with 0.1% (v/v) of alginate-coated light-expanded clay aggregates beads containing NH4+-reducing bacteria was used, removal efficiency of NH4+ by the full-scale intermittent aeration SBR (IA-SBR) was significantly different from both traditional intermittent aeration SBR (T-SBR) and the continuous aeration SBR with AL beads containing NH4+-reducing bacteria (P<0.05). In summary, the IA-SBR with AL beads can significantly promote removal efficiency of NH4+ on farm. [ABSTRACT FROM AUTHOR]

Aerobic granulation from floccular sludge is difficult to detect in first stages with the naked eye. This work proposes a combination of multi-way principal components and case-based reasoning to predict the granulation state of a sequencing batch reactor, based solely on the on-line registered profiles of common sensors (i.e. pH, dissolved oxygen and oxidation-reduction potential). The methodology is able to discriminate between two active sludge granularities (floccular and granular). Two different scenarios are presented: one in which both granularities are present, and another scenario for which the granular state is not initially available. Analysis reported pH as the key variable in the transition between both states according to its variation, and that, in general, the granularity of the process can be correctly predicted at the end of the anaerobic phase. This methodology improves process monitoring capabilities during granulation and is an on-line alternative to a microscope analysis before the batch release. [ABSTRACT FROM AUTHOR]

Denitrifying activities and nitrous oxide (N2O) emission during denitrification can be affected by copper concentrations. Different denitrifiers were acclimated in sequencing batch reactors with acetate or methanol as the electron donor and nitrate as the electron acceptor. The effect of copper concentrations on the denitrifying activity and N2O emission for the acclimated denitrifiers was examined in batch experiments. Denitrifying activities of the acclimated denitrifiers declined with increasing copper concentrations, and the copper concentration exhibited a higher effect on denitrifiers acclimated with acetate than those acclimated with methanol. Compared with the control without the addition of copper, at the copper concentration of 1 mg/L, the acetate utilization rate reduced by 89% for acetate-acclimated denitrifiers, while the methanol utilization rate only reduced by 15% for methanol-acclimated denitrifiers. Copper also had different effects on N2O emission during denitrification carried out by various types of denitrifiers. For the acetate-acclimated denitrifiers, N2O emission initially increased and then decreased with increasing copper concentrations, while for the methanol-acclimated denitrifiers, N2O emission decreased with increasing copper concentrations. [ABSTRACT FROM AUTHOR]

An anaerobic membrane bioreactor and aerobic granulation technologies were tested at laboratory scale to treat winery wastewater, which is characterised by a high and variable biodegradable organic load. Both technologies have already been tested for alcohol fermentation wastewaters, but there is a lack of data relating to their application to winery wastewater treatment. The anaerobic membrane bioreactor, with an external microfiltration module, was started up for 230 days, achieving a biogas production of up to 0.35 L CH4 L-1 d-1 when 1.5 kg COD m-3 d-1 was applied. Average flux was 10.5 L m-2 h-1 (LMH), obtaining a treated effluent free of suspended solids and a chemical oxygen demand (COD) concentration lower than 100 mg COD L-1. In contrast, the aerobic granular sequencing batch reactor coped with 15 kg COD m-3 d-1, but effluent quality was slightly worse. Aerobic granulation was identified as a suitable technique to treat this kind of wastewater due to excellent settleability, high biomass retention and a good ability to handle high organic loads and seasonal fluctuations. However, energy generation from anaerobic digestion plays an important role, favouring anaerobic membrane bioreactor application, although it was observed to be sensitive to sudden load fluctuations, which led to a thorough pH control and alkali addition. [ABSTRACT FROM AUTHOR]

Membrane fouling needs to be mitigated for widespread use of membrane bioreactors (MBRs). It has been pointed out that particles with small sizes found in supernatants (sub-micron particles) of mixed liquor suspensions of MBRs are important in the evolution of membrane fouling of this technology. However, information on characteristics of sub-micron particles in MBRs is still insufficient. In this study, a pilot-scale MBR treating municipal wastewater was used to investigate and characterize sub-micron particles in an MBR and to identify the size fraction(s) responsible for irreversible fouling in an MBR. It was clearly shown that characteristics of sub-micron particles in the MBR varied considerably depending on their sizes. Results of Fourier transform infrared (FTIR) analysis and monosaccharide analysis suggested that irreversible fouling in this study was mainly caused by the specific size fraction of 0.1-0.45 μm, which was close to the size of micropores of the membrane used. Pore plugging might explain this to some extent. [ABSTRACT FROM AUTHOR]

This study developed a simple numerical model for nitrogen removal in biofilters, which was designed to enhance simultaneous nitritation and anaerobic ammonium oxidation (anammox). It is the first attempt to simulate anammox together with two-step nitrification in natural treatment systems, which may have different kinetic parameters and temperature effects from conventional bioreactors. Prediction accuracy was improved by adjusting kinetic coefficients over the startup period of the biofilters. The maximum rates of nitritation and nitrite oxidation increased linearly over time during the startup period. Simulations confirmed successful enhancement of simultaneous nitritation and anammox (SNA) in the biofilters, with anammox contributing 35% of ammonium removal. Effluent ammonium concentration was affected by influent ammoriium concentration and the maximum nitritation rate, and was insensitive to the maximum nitrite oxidation rate and anammox substrate factor. Ammonium removal via SNA was likely limited by biomass of aerobic ammonia oxidizing bacteria in the biofilters. The developed model is a promising tool for studying the dynamics of nitrogen removal processes including SNA in natural treatment systems. [ABSTRACT FROM AUTHOR]

In this study the anaerobic treatability of amoxycillin (AMX) was investigated in a laboratory-scale anaerobic multi-chamber bed reactor (AMCBR)/aerobic continuously stirred tank reactor (CSTR) system. The chemical oxygen demand (COD) and AMX removal efficiencies were around 94% in the AMCBR reactor at hydraulic retention times (HRTs) between 2.25 and 5.5 days. Decreasing the HRT appeared not to have a significant effect on the performance of the AMCBR up to a HRT of 1.13 days. The maximum methane production rate and methane percentage were around 1,100-1,200 mL/day and 55%, respectively, at HRTs between 2.25 and 5.5 days. The decrease in HRT to 1.5 days decreased slightly the gas productions (1,000 mLlday and 500 mL for total and methane gases) and methane percentage (45%). The AMCBR recovered back to its baseline performance within a couple of days. The acute toxicity of 150 mg/L AMX was monitored with Daplinia magna, Lepistes sp., and Vibrio fischeri acute toxicity tests. The acute toxicity removals were 98, 96 and 96% for V. fischeri, D. magna and Lepistes sp. in the effluent of the sequential system treating 150 mg/L AMX at HRTs of 2.25-5.5 days. Among the trophic organisms used in the acute toxicity tests the most sensitive organism was found to be bacteria (V. fischeri) while the most resistant organism was found to be fish (Lepistes sp.). [ABSTRACT FROM AUTHOR]

Composting is one of the technologies recommended for pre-treating industrial eggshells (ES) before its application in soils, for calcium recycling. However, due to the high inorganic content of ES, a mixture of biodegradable materials is required to assure a successful procedure. In this study, an adequate organic blend composition containing potato peel (PP), grass clippings (GC) and wheat straw (WS) was determined by applying the simplex-centroid mixture design method to achieve a desired moisture content, carbon: nitrogen ratio and free air space for effective composting of ES. A blend of 56% PP, 37% GC and 7% WS was selected and tested in a self heating reactor, where 10% (w/w) of ES was incorporated. After 29 days of reactor operation, a dry matter reduction of 46% was achieved and thermophilic temperatures were maintained during 15 days, indicating that the blend selected by statistical approach was adequate for composting of ES. [ABSTRACT FROM AUTHOR]

Completely autotrophic nitrogen removal over nitrite (CANON) is a cost-effective nitrogen removal process. Implementation of the CANON process relies on the cooperation of ammonium-oxidizing and Anammox bacteria, as well as the inhibition of nitrite-oxidizing bacteria. Strict limitations on dissolved oxygen (DO) concentration in the reactor, and the addition of sufficient inorganic carbon in the influent, were adopted as the main operational strategies. The reactor was fed with synthetic inorganic wastewater composed mainly of NH4+-N, and operated for 106 days. Stable nitrogen removal rates (NRR) of around 1.4 kg N m-3 d-1 were obtained at ambient temperature. Morphological characteristics and analysis of bacterial community confirmed the formation of functional outer aerobic and inner anaerobic granular sludge, providing evidence of stable nitrogen removal. [ABSTRACT FROM AUTHOR]

Mixed culture fermentation is an alternative to pure culture fermentation for production of biofuels and valuable products. A glucose-fed, continuous reactor was operated cyclically to a central pH of 5.5 from a number of precedent pHs, from 4.5 to 7.5. At each pH, stable chemical production was reached after 2 retention times and was held for least 2 further retention times prior to the next change. Bacterial groups were identified by phylogenetic analysis of 16S rRNA gene clones. Bacterial community dynamics were monitored by terminal-restriction fragment length polymorphism. More ethanol was produced at high pH, and more butyrate at lower pH. At pH 5.5, the product spectrum was not measurably influenced by precedent pH but showed seemingly random changes. The impact of precedent pH on community structure was more systematic, with clear indications that when the pH was returned to 5.5, the bacterial group that was dominant at the precedent pH remained at high abundance. This result is important, since it indicates a decoupling between microbial function (as indicated by product spectrum), and community structure. More work is needed to determine the longevity of this hysteresis effect. There was evidence that groups retained their ability to re-emerge even after times of low abundance. [ABSTRACT FROM AUTHOR]

Sulfide-oxidizing autotrophic denitrification is an advantageous alternative over heterotrophic denitrification, and may have potential for nitrogen removal of low-strength wastewaters, such as anaerobically pre-treated domestic sewage. This study evaluated the fundamentals and kinetics of this process in batch reactors containing suspended and immobilized cells. Batch tests were performed for different NOx -/S2- ratios and using nitrate and nitrite as electron acceptors. Autotrophic denitrification was observed for both electron acceptors, and NOx -/S2- ratios defined whether sulfide oxidation was complete or not. Kinetic parameter values obtained for nitrate were higher than for nitrite as electron acceptor. Zero-order models were better adjusted to profiles obtained for suspended cell reactors, whereas first-order models were more adequate for immobilized cell reactors. However, in the latter, mass transfer physical phenomena had a significant effect on kinetics based on biochemical reactions. Results showed that sulfide-oxidizing autotrophic denitrification can be successfully established for low-strength wastewaters and have potential for nitrogen removal from anaerobically pre-treated domestic sewage. [ABSTRACT FROM AUTHOR]

The treatment of grey water in two upflow anaerobic sludge blanket (UASB) reactors, operated at different hydraulic retention times (HRTs) and temperatures, was investigated. The first reactor (UASB-A) was operated at ambient temperature (14-25 °C) and HRT of 20, 12 and 8 h, while the second reactor (UASB-30) was operated at controlled temperature of 30 °C and HRT of 16, 10 and 6 h. The two reactors were fed with grey water from 'Flintenbreite' settlement in Luebeck, Germany. When the grey water was treated in the UASB reactor at 30 °C, total chemical oxygen demand (CODt) removal of 52-64% was achieved at HRT between 6 and 16 h, while at lower temperature lower removal (31-41%) was obtained at HRT between 8 and 20 h. Total nitrogen and phosphorous removal in the UASB reactors were limited (22-36 and 10-24%, respectively) at all operational conditions. The results showed that at increasing temperature or decreasing HRT of the reactors, maximum specific methanogenic activity of the sludge in the reactors improved. As the UASB reactor showed a significantly higher COD removal (31-64%) than the septic tank (11-14%) even at low temperature, it is recommended to use UASB reactor instead of septic tank (the most common system) for grey water pre-treatment. Based on the achieved results and due to high peak flow factor, a HRT between 8 and 12 h can be considered the suitable HRT for the UASB reactor treating grey water at temperature 20-30 °C, while a HRT of 12-24 h can be applied at temperature lower than 20 °C. [ABSTRACT FROM AUTHOR]

The characteristics of self-forming dynamic membrane (DM) in sequencing bioreactors under different sludge retention times (SRT) (SRT = 5, 10, 20, 40, 60 days) were studied using a scanning electron microscope, particle sizing distribution and others. The results indicated that the SRT has an evident effect on the characteristics of DM. The content of extracellular polymeric substances and protein decreased with the increase of SRT. The change of polysaccharide was small regardless of SRT. The filtration resistance of the DM was divided into two stages: an initial slowly-rising stage and a fast-rising later stage which were both irrespective of SRT. With the increase of SRT, the filtration resistance increase extent reduced and the running cycle became longer. Compared to the lower SRT, the particle size distribution of mixed liquor and DM has a decreasing trend at higher SRT. The average particle size of DM was larger than that of the mixed liquor irrespective of SRT. The amounts and types of microorganisms on the surface of DM were more abundant as SRT increased. Low SRT produced the DM surface with some Cocci while the high SRT gave the DM dominated with Cocci, Filamentous and Bacillus. [ABSTRACT FROM AUTHOR]

This article evaluates the performance of 10 large scale upflow anaerobic sludge blanket (UASB) sewage treatment plants (STP) located in semi-tropical areas, 7 plants were located in Brazil, 2 in India and 1 in the Middle East. In addition to the UASB, essential functional units of the STP which potentially impact on the UASB are also evaluated. Most grit removal systems were performing adequately, however in one plant very little grit was being removed. This could have serious implications for the performance of the plant as in a relatively short period of time the reactors could become full of grit. The performance results obtained in this study (COD, BOD and TSS removal efficiencies) are compared to the results of recent literature publications and also to the results of some early pilot and full scale studies. The results found here are broadly similar to those result reported in the recent literature but show a lower performance in comparison with the early pilot scale plants. Factors such as improper design, poor operating procedures, insufficient maintenance and the presence of high sulphate concentrations have been identified as the main reasons for the lower performance. [ABSTRACT FROM AUTHOR]

Laboratory-scale experiments were conducted to investigate the removal and fate of estrogens 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) in an anaerobic-anoxic-oxic (AAO) activated sludge system. Estrogen concentrations in the aqueous and solid phases in each reactor of AAO system were analyzed separately. E2 was not detected in the final effluent. The anaerobic, anoxic and oxic reactors accounted for 71%, 7% and 22% of the overall E2 removal, respectively. The overall EE2 removal efficiency was about 80%, and the anaerobic, anoxic and oxic reactors were responsible for 44%, 8% and 48% of the overall EE2 removal, respectively. In anaerobic unit, sorption was the dominant mechanism for the removal of E2 and EE2. While E2 was degraded in all the three units of the AAO system, EE2 was only degraded in the anoxic and aerobic units. Biodegradation is important for the fate of E2 compared to sorption. Of the total influent E2 in the AAO system, 99.99% was biodegraded and 0.01% remained in the waste sludge. Nevertheless, both sorption and biodegradation play important roles in the removal of EE2. Of the total influent EE2, 79.1% was degraded by activated sludge, 19.9% was discharged in the effluent and 1% remained in the waste sludge. [ABSTRACT FROM AUTHOR]

Twelve years after the first full scale municipal application in Europe of membrane bioreactor (MBR) technology, the process is now accepted as a technology of choice for wastewater treatment, and the market is showing sustained growth. However early misconceptions about the technology are persistent and false statements are commonly encountered in articles and conferences, generating unnecessary research efforts or even fuelling either fascination or scepticism with regards to the technology, which is ultimately detrimental to the perception of the process by water professionals. We try to provide some factual and rational clarifications on ten issues which are often wrongly reported about MBR technology. [ABSTRACT FROM AUTHOR]

The goal of this study was to determine whether ozone can be used to suppress bacterial growth in operating a white rot fungi reactor system. The effects of ozone dose on the activity of manganese peroxidase (MnP) and on the death rate of Escherichia coli were investigated. The results showed that at ozone dose of 0.98 mg/L the MnP activity was not affected after 40 mm continuous treatment while the Escherichia coli inactivation rate can reach 99.9% after 30 mm; In addition, the MnP that exposed to ozone dose of 1.56 mg/L for 40 mm maintained their activity for decolourization of Methyl Orange. After 16 h, the decolorization rate of Methyl Orange was about 41%. These results showed that MnP have the ability to resist to some extent the attack of ozonization, which suggest that ozone might have its potential in suppressing the bacteria contamination in operating the white rot fungi reactor. [ABSTRACT FROM AUTHOR]

This study investigated the effect of organic carbon source on ammonia oxidizing community in single sludge laboratory scale sequencing batch reactors (SBR). Two sequencing batch reactors performing simultaneous carbon oxidation and nitrification were operated. Operationally and functionally, these two reactors were identical, except that one reactor was fed peptone and sodium acetate, and the other was fed glucose and sodium acetate as external organic carbon sources. The peptone-fed reactor had 98.1±1.84% COD removal and 97.3±6.69% NH3-N oxidation. The glucose-fed reactor had 99.1±1.29% COD removal and 99.4±0.76% NH3-N oxidation. The reactor fed with peptone, a complex organic carbon source comprised of enzymatic digests of animal proteins, had greater diversity in both the heterotrophic bacterial community and the ammonia oxidizing bacteria community than in the reactor fed with glucose, a simple sugar as evidenced by automated ribosomal intergenic spacer analysis (ARISA) and terminal restriction fragment length polymorphism (TRFLP) experiments respectively. [ABSTRACT FROM AUTHOR]

Sludge characteristics associated with filterability as well as the removal of a natural estrogen 17β-estradiol (E2) and a synthetic estrogen 17α-ethyinylestradiol (EE2) were investigated in submerged membrane bioreactors (MBR) with and without the addition of powdered activated carbon (PAC) under the same experimental conditions. Positive impacts of PAC dosing on membrane fouling and the removal of E2 and EE2 were demonstrated over a six months stable operational period. Experimental results showed that PAC dosing resulted in lower concentrations of soluble extracellular polymeric substances (EPS) and colloidal total organic carbon (TOC) in the PAC-MBR sludge. The average soluble EPS and colloidal TOC concentrations in the PAC-MBR sludge was 60.1% and 61.8% lower than the control MBR sludge, respectively. Regardless of PAC dosing, concentrations of colloidal TOC were strongly related to concentrations of soluble EPS and soluble carbohydrates in the sludge. In addition, the mean flocs size of the sludge with PAC dosing was shifted from 49.4μm to 60.3μm. PAC dosing in the MBR increased the removal rates of E2 and EE2 by 3.4% and 15.8%, respectively. [ABSTRACT FROM AUTHOR]

A novel photocatalyst based on TiO2 nanoparticles was developed for application in fluidised bed photocatalytic reactors for water treatment. The mechanically robust photocatalyst consists of composite spheres made of TiO2 nanoparticles and TiO2 commercial powder. X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area analysis (BET) were used to characterise the catalyst. The photocatalytic activity was evaluated using model pesticide micro-pollutant. A complete model comprised of radiation, kinetic, and reactor bed models was also developed, allowing for detailed analysis of the photoreactor. [ABSTRACT FROM AUTHOR]

The main objective of this work was to investigate the filterability of MBR sludge and its mixture with conventional activated sludge (CAS). In addition, the impacts of type and dose of various polyelectrolytes, filter type and sludge properties on the filterability of both MBR and Mixed sludges were determined. Specific cake resistance (SCR) measured by the Buchner funnel filtration test apparatus and the solids content of the resulting sludge cake were used to assess the dewaterability of tested sludges. The type of filter paper used in Buchner tests affected the results of filterability for MBR, CAS and Mixed sludges. SCR values and optimum polyelectrolyte doses increased with increasing MLSS concentrations in the MBR, which suggested that increase in MLSS concentrations accompanied by increases in EPS and SMP concentrations and a shift toward smaller particles caused poorer dewaterability of the MBR sludge. The significant differences observed among the filterability of CAS and MBR sludges suggested that MLSS alone is not a good predictor of sludge dewaterability. Combining CAS and MBR sludges at different proportions generally improved their dewaterability. Combining MBR sludges having typically high MLSS and EPS concentrations with CAS having much lower MLSS concentrations may be an option for full-scale treatment plants experiencing sludge dewaterability problems. Better filterability and higher cake dry solids were achieved with cationic polyelectrolytes compared to anionic and non-ionic ones for all sludge types tested. [ABSTRACT FROM AUTHOR]

The State of Washington has found that the Spokane River is DO impaired, and is requiring dischargers to reduce phosphorus inputs to the river. Spokane County elected to build a new water recovery facility with a target effluent total phosphorus level of 50μg/L on a seasonal average basis. Spokane County elected to use a private company to design/build and operate their facility. The very low nutrient requirements, and lack of historical operating information, necessitated an integrated approach to the nutrient removal design while considering the risks and benefits of the various treatment options. The process selection evaluated membrane bioreactors and tertiary membranes for the primary liquids process in combination with chemical and/or biological phosphorus removal. The final process selection included chemically enhanced primary treatment, membrane bioreactor with metal salts, and dewatering liquor treatment with an innovative post aerobic digestion step. [ABSTRACT FROM AUTHOR]

The performance of a mesophilic UASB reactor was studied for the treatment of sugar cane mill wastewater previously pre-treated for solid separation. The experimental work was carried out in a reactor with 80 L total volume. Four organic loads were applied and the process performance was evaluated during two months for each experimental stage. Removal efficiencies higher than 90% were obtained with organic loads up to 16 kgCODm-3 d-1. Stable process performance and high biogas production were obtained. The COD removal rate increased substantially with the load increase to 24 kg CODm-3 d-1. However, the obtained removal was of only 78-82%, which can be attributed to the accumulation of volatile organic acids. The kinetic coefficients were obtained using first order model for the substrate removal rate and Monod's equation for bacteria specific growth rate. The UASB reactor is a good option for the biological treatment of pre-treated sugar cane mill wastewaters. The discharge requirements for COD concentration can be accomplished if the reactor is operated at a low organic load of 4 kgCODm-3 d-1. At higher loads, an additional biological treatment stage is needed. [ABSTRACT FROM AUTHOR]

The goal of this study was to assess the effect of different modes of operation and configurations of Anaerobic Sequencing Batch Reactors (ASBRs) treating phenolic wastewater. Several lab-scale reactors were used in the mesophilic range. The reactors were fed with synthetic wastewater with a COD of 5 g/L using phenol as a carbon source (variable concentration) and glucose as a co-substrate. One and two-phase (hydrolytic/acidogenic-methanogenic) systems in batch and fed-batch operation were evaluated. The one-stage reactor operated by the fed batch (which was the only configuration using phenol as a sole carbon source), presented better results for the removal of phenol, reaching 100% removal in 10 days at a concentration of 210 mg/L. The two-stage configuration had removal percentages near 100%, but the methanogenic reactor presented greater degradation of the remaining phenol not removed in the hydrolytic/acidogenic reactor. ASBRs might be a feasible alternative to treat this type of effluent due to their operational flexibility. [ABSTRACT FROM AUTHOR]

In our experimental work the pilot plant and full scale anaerobic bioreactors of a communal sewage treatment plant were tested by applying usual control parameters (pH, volatile acid content, alkalinity, gas composition), and enzyme activity (dehydrogenase, protease, lipase) measurements. Influence of temperature change was examined in pilot plant scale, while the effect of alteration in specific organic matter load both in pilot and full scale. Among the control parameters only the change of the volatile acid concentration reflected the occurred influences. During the temperature varying experimental phase the dehydrogenase enzyme activity excellently indicated the influence of the different conditions. The effect of altering substrate load onto the gas production was also well followed by the enzyme activity data (mainly protease, lipase), and more rapidly than by measuring volatile acid concentration. In practice it is expedient to use enzyme activity measurements in those cases, when changes in the substrate composition and load are frequent. Another advantage of these tests is that they can be carried out quickly and at a relative low cost. [ABSTRACT FROM AUTHOR]

Municipal wastewater was amended with organic garbage leachates at a concentration around 700mgCODsoluble/L and fed to three different anaerobic systems to compare their performance: a down flow fluidized bed (DFFB), an expanded granular sludge bed (EGSB) and a zeolite-packed anaerobic filter reactor (ZPF). The DFFB and EGSB reactors were operated at HRT of 6 and 4 h and the ZPF reactor at 12 and 36 h. Organic loads rate for the DFFB reactor were 2.3 ± 0.9 and 4.8 ± 1.8 gCOD/L·d, with removal efficiencies around 40% and a methane productivity of 0.2 ± 0.03 L/Lreactor·d. For the EGSB reactor, organic loads tested were 2.1 ± 0.9 and 4.3 ± 1.3 gCOD/L·d, removal efficiencies attained were of 77.6 ± 12.7% and 84.4 ± 4.9%, respectively at both conditions and total suspended solids were removed in 54.6 ± 19.3%, while methane productivity at 4 h HRT was of 1.29 ± 0.4 L/Lreactor·d. The ZPF reactor was operated at lower organic loading rates, 1.4 ± 0.27 and 0.42 ± 0.13 gCOD/L·d and attained removal efficiencies of 48 ± 18% and 83 ± 8%, respectively, reaching a methane productivity of 0.21 ± 0.09 and 0.12 ± 0.04 L/Lreactor·d, 83 ± 8.0% of total suspended solids were retained in the reactor and as HRT was increased ammonium concentrations increased in 39%. Specific methanogenic activity in all systems was around 0.2 gCOD-CH4/gVSS d. [ABSTRACT FROM AUTHOR]

Models currently used have been developed to describe the storage response in the activated sludge process. In these models the distribution of the substrate flux between growth and storage is an empirical function. rRNA-structured biomass models are proposed to describe the metabolic status of cells in view of predicting the growth response (dμ/dt) of cells in activated sludge process. The autocatalytic reaction rate of the synthesis of the PSS component (rRNA) can provide a mechanistic explanation for the growth response and the growth lag phase. The proposed models were able to describe and predict properly the growth response of the biomass in various types of reactor. Such models could be more widely applicable by using intrinsic model parameters. This would be a key improvement for as it would lead to improved models for design. [ABSTRACT FROM AUTHOR]

The present study addresses potential of water hyacinth for treating small-scale dairy wastewater to satisfy effluent standards for disposal into public sewers. The batch experiments were conducted on dairy wastewater using reactor with water hyacinth and without water hyacinth. The Chemical Oxygen Demand (COD) was varied from 507 mg/L to 4,672 mg/L and the maximum Hydraulic Retention Time (HRT) adopted was 8 days. The loss of water due to evapo-transpiration and evaporation was also measured. The water hyacinth system performed better when initial COD concentration was maintained less than 1,672 mg/L for six days HRT. The performance of water hyacinth system was more effective than reference by 30% to 45% for COD removal. However, water hyacinth had no significant impact in reducing Total Dissolved Solids (TDS). The evapo-transpiration loss was almost double than the evaporation loss. The first order reaction kinetics was applicable and reaction rate parameters were estimated for various organic strengths of wastewater. The reaction rate parameters for water hyacinth system were three times higher than a system without water hyacinth and also found to vary with initial COD values. Water hyacinth can be adopted to treat dairy wastewater from small-scale dairy effectively for disposal into public sewers. [ABSTRACT FROM AUTHOR]

The ADM1 is applied to simulate the behaviour of an Upflow Anaerobic Sludge Blanket Reactor (UASB) treating blood powder (spray dried blood meal) wastewater. Considering a completely mixed liquid phase, the model is defined by a set of differential equations which can be numerically solved. Experimental data allows validating the output of the model which is then used for performing numerous simulations. A single reactor is compared to a series of two identical reactors of half the volume each. For the same total hydraulic retention time, the series reaches an outlet concentration 74% inferior to that of the single reactor. Furthermore, for the same total conversion the volume required by the series is 43% of that of the single reactor. [ABSTRACT FROM AUTHOR]

A Moving Bed Bioreactor (MBBR) was operated during 333 days. Two different effluents were fed in six different phases. Phases I and II were fed with effluent where Pinus radiata was used as raw material, while phases III to VI were fed with effluent where Eucalyptus globulus was used as raw material. The HRT was reduced from 85 to 4 h, and the BOD5:N:P ratio (100:5:1, 100:3:1 and 100:1:1) was also simultaneously evaluated as an operation strategy. When MBBR was operated with Pinus radiata influent, the performance presents a high BOD5 removal level (above 95%), although COD removal is below 60%. Most of the recalcitrant COD contained in the effluent has a molecular weight higher than 10,000 Da. When MBBR was operated with Eucalyptus globulus influent, the performance is around 97.9-97.6% and 68.6-65.1% for BOD5 and COD, respectively (with HRT up to 17 h). In the Pinus radiata and Eucalyptus globus effluents, the color was mainly found in the molecular weight fraction up to 10,000 Daltons. [ABSTRACT FROM AUTHOR]

Fouling is still one of the main issues in the operation of membrane bioreactors (MBRs). While most attention has been paid to extracellular polymeric substances (EPS) and soluble microbial products (SMP) in the bulk solution, changes in membrane filterability may be more adequately described by the structural characteristic of the fouling layer or biofilm. This study shows that membrane filterability and the rise in TMP is associated to the changes in the biofiom structure, and polysaccharides may be the most significant fraction that affects fouling. [ABSTRACT FROM AUTHOR]

Two 6-L submerged anaerobic membrane bioreactors (SAMBR) with SRT of 30 and 60 d (denoted as R30 and R60, respectively) were set up and operated for five months, with a mixture of glucose as substrate. Feasibility of SAMBR was studied for treatment of low-strength wastewater. First two months were identified as acclimation stage. A COD removal efficiency was achieved stably at around 99% and biogas productions were maintained at 0.023 and 0.028 L CH4/gMLVSSzd for R30 and R60, respectively. Even though R60 contained higher MLVSS concentration, no significant difference of treatment performances between both reactors was found due to the low organic loading rate and high purification function of membrane. In the investigation of membrane fouling, less irreversible fouling was observed for R30 compared to R60. High non-flocculent concentration of R60 would be responsible for membrane internal pore blocking and deteriorated effluent quality. [ABSTRACT FROM AUTHOR]