Anaerobic treatment of domestic wastewater using an anaerobic fixed-bed loop reactor

Incorporation of anaerobic processes into wastewater treatment trains minimizes amount and enhances stability of excess sludge, but lowers energy consumption. Objectives of this study were to develop a pilot-scale anaerobic fixed-bed loop (AFBL) reactor, to select critical parameters and to investigate feasibility and performance when treating municipal wastewater under real field conditions. Hydraulic residence tirnes (HRTs) of 0.23, 0.28 and 0.36 days were implemented at temperatures of 25 degrees C, 30 degrees C and 35 degrees C, respectively. The AFBL reactor was fed with raw wastewater and operated for 165 days. Results clearly show that the proposed pilot-scale AFBL reactor removes particulate COD (CODp), soluble COD (CODs), total suspended solids (TSS), volatile suspended solids (VSS) and total Kjedahl nitrogen (TKN), and produces biogas under real field conditions, which means that its application is feasible. Average COD and TSS removal was about 52% and 57%, respectively, whereas biogas production increased with temperature increase and HRT decrease. The higher biogas production was recorded at HRT of 0.23 days and temperature of 35 degrees C. Application of the AFBL reactor is suggested as a pre-treatment step to the conventional municipal wastewater treatment, especially in decentralized areas experiencing population fluctuations, such as Greek islands during the warm, high tourist season. At this time, heating would not be necessary and more energy would be saved

Effect of the Oxidative Phosphorylation Uncoupler Para-Nitrophenol on the Activated Sludge Community Structure and Performance of a Submerged Membrane Bioreactor

In this work, the metabolic uncoupler para-nitrophenol (pNP) was applied to suppress excess sludge production and to investigate its effects on the system’s performance and activated sludge community structure. The COD removal efficiency decreased from 99.0% to 89.5% prior to and after pNP addition, respectively. Application of pNP transiently reduced NH4+-N, NO3−-N and NO2−-N removal efficiencies, suggesting partial inhibition of both nitrifying and denitrifying activity. However, no changes in the relative abundance of the nitrifying bacteria occurred. Phosphorus removal efficiency was sharply reduced after pNP addition, as the consequence of hydrolysis of stored cell reserves. Tetrasphaera, a key polyphosphate accumulating organism, was also affected by the addition of pNP, a fact that highly influenced system’s ability to remove phosphorus. A drastic drop in Soluble Microbial Products (SMP) and Extracellular Polymeric Substances (EPS) was also detected shortly after the introduction of the uncoupler. On the other hand, MBR’s physicochemical parameters were restored to initial values a week after the addition of pNP. Moreover, remarkable changes in beta-diversity were noted after pNP addition. An increase of Bacteroidetes, Gammaproteobacteria and Firmicutes over Actinobacteria and Alphaproteobacteria was also observed after pNP addition

Membrane Fouling Monitoring in a Submerged Membrane Bioreactor

Use of Membrane Bioreactor (MBR) technology for municipal wastewater treatment has been increased in recent years, as it successfully overcomes the disadvantages of the conventional activated sludge process. Membrane fouling is the major disadvantage of MBRs and leads to decreased membrane performance and expanded operational expenses. In this study, fouling was monitored in a pilot-scale submerged MBR system fed with municipal wastewater. TMP was directly measured on the membrane module during the operation. To control TMP increase owing to biosolids accumulation on membrane surface, successive backwashes and air-cross flow velocity increase were applied. These measures lowered TMP and improved flux

The effect of activated carbon addition on membrane bioreactor processes for wastewater treatment and reclamation - a critical review

This review concentrates on the effect of activated carbon (AC) addition to membrane bioreactors (MBRs) treating wastewaters. Use of AC-assisted MBRs combines adsorption, biodegradation and membrane filtration. This can lead to advanced removal of recalcitrant pollutants and mitigation of membrane fouling. The relative contribution of adsorption and biodegradation to overall removal achieved by an AC-assisted MBR process can vary, and biological AC may not fully develop due to competition of target pollutants with bulk organics in wastewater. Thus periodic replenishment of spent AC is necessary. Sludge retention time (SRT) governs the frequency of spent AC withdrawal and addition of fresh AC, and is an important parameter that significantly influences the performance of AC-assisted MBRs. Of utmost importance is AC dosage because AC overdose may aggravate membrane fouling, increase sludge viscosity, impair mass transfer and reduce sludge dewaterability

Biodegradation Potential and Diversity of Diclofenac-degrading Microbiota in an Immobilized Cell Biofilter

Despite that diclofenac has been embodied to the European watch list of priority substances of concern, studies on diclofenac biodegradation are limited and the diversity of diclofenac-degrading microbiota remains unknown. In this work, an immobilized cell biofilter was constructed and operated to evaluate its effectiveness to depurate high strength diclofenac wastewater and to identify the diclofenac-degrading community accommodated in activated sludge by employing high-throughput sequencing techniques. After a two-month adaptation period, biofilter removal efficiencies reached values as high as 97.63 ± 0.62%, whereas utilization of diclofenac in the immobilized cell biofilter led to a drastic pH decrease. Based on Illumina sequencing, the major bacterial taxa identified in the immobilized cell biofilter were members of the species Granulicella pectinivorans and Rhodanobacter terrae, followed by members of the species Castellaniella denitrificans, Parvibaculum lavamentivorans, Bordetella petrii, Bryocella elongata and Rhodopseudomonas palustris. The ability of such taxa to utilize a wide range of carbon sources and to effectively adapt under acidic conditions seemed to be the main parameters, which favored their prevalence in the immobilized cell biofilter. In addition, Wickerhamiella was the predominant fungal taxon in the immobilized cell biofilter, which appears to be actively involved in diclofenac degradation in activated sludge systems

A Critical Review on the Microbial Ecology of Landfill Leachate Treatment Systems

Sanitary landfilling is still considered worldwide as one of the most common methods applied for the management of the municipal solid waste. As a consequence, vast amounts of landfill leachate are generated annually, which are characterized by variability in physicochemical composition, owing to the stabilization process that occurs over the years. However, sustainable management of landfill leachate is a challenging issue, due to diverse chemical composition and high concentration in heavy metals and xenobiotics. Despite the fact that several studies have been reported on the biotreatment of landfill leachate, only in recent years has the microbial composition in such systems have been examined. In the present review, the key role of the microbial ecology involved in depurification and detoxification of landfill leachate in activated sludge and anaerobic systems is interpreted and ecological considerations influencing landfill leachate treatment are stated. Apart from the assessment of landfill toxicity on certain model organisms, this work provides an extensive overview on microbial communities performing key biological processes during landfill leachate treatment, including nitrification-denitrification, anammox and anaerobic digestion. Moreover, microbial aspects affecting nutrient removal efficiency in such biosystems are discussed

Protozoan indicators and extracellular polymeric substances alterations in an intermittently aerated membrane bioreactor treating mature landfill leachate

<p>A membrane bioreactor was operated under intermittent aeration and various organic loading rates (OLR: 0.070, 0.159 and 0.291 g COD L⁻¹ d⁻¹) to remove carbon and nitrogen from mature landfill leachate, where external carbon source (glycerol) addition resulted in effective nitrate removal. A relative increase in soluble microbial product (SMP) over extracellular polymeric substances (EPS) was observed at the highest OLR and glycerol addition, whereas no membrane biofouling occurred. SMP (proteins and carbohydrates) and carbohydrate EPS correlated positively and negatively, respectively, with suspended solids and transmembrane pressure (TMP). Moreover, proteinous SMP significantly correlated with carbon and nitrogen load. Principal component analysis also revealed the influence of leachate organic and nitrogen content on biomass production, TMP and sessile ciliate densities. Although filamentous index (FI) was sustained at high levels (3–4), with <i>Haliscomenobacter hydrossis</i> being the main filamentous bacterium identified, no bulking phenomena occurred. High glycerol addition resulted in a rapid increase in sessile ciliate population. Increased <i>Epistylis</i> and <i>Vorticella microstoma</i> population was detected by microscopic examination during high glycerol addition, while a remarkable <i>Rhogostoma</i> population (supergroup Rhizaria) was identified by molecular techniques. The contribution of Rhizaria in nitrogen processes may lead to the dominance of <i>Rhogostoma</i> during landfill leachate treatment.</p

Water footprint and water pinch analysis techniques for sustainable water management in the brick-manufacturing industry

Brick-manufacturing is an intensive water-consuming industry that requires a sustainable and integrated water management strategy to reduce reliance on freshwater consumption. This study aims to develop a rigorous analytical tool based on water footprint principles and water pinch analysis techniques that can be used to manage and optimise water consumption. By performing thorough water audits, the water consumption footprint (the sum of blue and green water footprints) and the theoretical water pollution footprint (grey water footprint) were quantified. The total water consumption footprint of a brick is determined as 2.02 L, of which blue water is identified as 1.71 L (84.8%) and green water as 0.31 L (15.2%). The theoretical grey water footprint of a brick was found to be 1.3 L, a value that would have been higher if in-situ wastewater treatment had not been operated before effluent discharge. In order to reduce the water footprint of a brick, water pinch analysis techniques were applied for the brick-manufacturing processes. Two water recovery schemes were explored, i.e. direct re-use/recycle and water regeneration. For the former, water targeting was first carried out using the material recovery pinch diagram. Next, an algebraic technique was utilised for the targeting of water regeneration, where an interception unit is used to partially purify the water sources for further re-use/recycle. The network that fulfils the water flow rate targets was then designed using the nearest neighbour algorithm. The calculation indicates that direct re-use/recycle scheme reduces with the standard water consumption footprint reduced only by 15.6%. Water regeneration scheme, on the other hand improved the current value (which relies on an unsystematic water regeneration scheme) by 56.4%. The analysis clearly shows that the water consumption footprint of a brick is improved when the brick-manufacturing industry operates sustainable water management strategies. This study, a first of its kind, demonstrates that integration of water pinch analysis coupled with water footprint concepts, provides a robust and effective tool for the manufacturing industries that aim for sustainable water consumption