Osmotic membrane bioreactor (OMBR) is an emerging technology integrating a forward osmosis (FO) process into a membrane bioreactor (MBR). This technology has been gaining increasing popularity in ...wastewater treatment and reclamation due to its excellent product water quality, low fouling tendency and high fouling reversibility over conventional MBRs. In the past decade especially the last 3 years, novel insights and significant advancements have been achieved in many aspects of OMBR accompanied with greatly increased number of published papers. This paper attempts to critically review the recent developments in OMBRs and to present a clear outline for further studies. Firstly, OMBR fundamentals including its configuration and FO process are presented. Subsequently, performance of OMBRs is summarized and compared to conventional MBRs. Additionally, mechanisms, impacts and mitigations of salt accumulation and membrane fouling related to the core challenge of low water flux in OMBRs are addressed. Finally, future research prospects are discussed in order to further improve OMBR technology and drive it from laboratory research to real practical applications.
•OMBR has emerged as one of the highly efficient wastewater treatment technologies.•OMBR fundamentals including its configuration and FO process are presented.•Performance of OMBRs is summarized and compared to conventional MBRs.•Salt accumulation and membrane fouling as the main challenges of OMBRs are discussed.•Future research prospects for further improving OMBR technology are outlined.
In this study, potential of neural-signal electroencephalogram (EEG)-based methods for enhancing human-building interaction under various indoor temperatures were explored. Correlations between EEG ...and subjective perceptions/tasks performance were experimentally investigated. Machine learning-based EEG pattern recognition was further studied. Results showed that the EEG frontal asymmetrical activity related well to the subjective questionnaire and objective tasks performance, which can be used as a more objective metric to corroborate traditional subjective questionnaire-based methods and task-based methods. Machine learning-based EEG pattern recognition with linear discriminant analysis (LDA) classifiers can well classify the different mental states under different thermal conditions. Utilization of the EEG frontal asymmetrical activities and the machine learning-based EEG pattern recognition method as a feedback mechanism of occupants, which can be implemented on a routine basis, has a great potential to enhance the human-building interaction in a more objective and holistic way.
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•EEG-based methods as a feedback mechanism of occupants.•EEG-based methods for enhancing human-building interaction.•EEG relates well to subjective questionnaire and objective tasks performance.•EEG pattern recognition well classify different mental states.
Thermal processing of sewage sludge (SS) has received increasing attention in recent years. Thermal processes valorise the carbon rich organic fraction of SS, while effectively reducing SS volume. ...However, the fate and distribution of heavy metals (HMs) during thermal processing of SS is an important issue to address because it has impact on the generation of secondary pollutants and the environmental acceptability of the residues for reuse and reclamation. The refractory metals (thermally stable, i.e. Cr, Mn and Ni) are less volatile at typical temperature ranges (200–1100 °C) of thermal processes, and they are enriched in the residues. On the contrary, HMs with lower thermal stability (i.e. Hg, Cd, As and Pb) are prone to volatilisation. However, volatilisations and enrichments of HMs in the residues strongly depend on the characteristics of SS and nature of the thermal process. This review article discusses the volatilisation, enrichment and speciation (or stabilisation) of HMs in the residues formed during thermal processing of SS (incineration, pyrolysis, gasification and hydrothermal treatment). First, it summarises the fundamental aspect of SS in each thermal process. The influencing factors on the fate and distribution of HMs are discussed in terms of process principles, reactor types, operating conditions, pre-treatment of SS, use of additives and co-processing with secondary feedstocks. The use of advanced analytical techniques and modelling tools to analyse the complexity of HMs redistribution during thermal processing is described. Practical and economic challenges associated with HMs in SS during operation of full-scale thermal processing facilities are also addressed. Finally, a brief comparison of HMs redistribution and stabilisation during SS incineration, gasification, pyrolysis and hydrothermal treatment is provided.
The microbial safety of swimming pool waters (SPWs) becomes increasingly important with the popularity of swimming activities. Disinfection aiming at killing microbes in SPWs produces disinfection ...by-products (DBPs), which has attracted considerable public attentions due to their high frequency of occurrence, considerable concentrations and potent toxicity. We reviewed the latest research progress within the last four decades on the regulation, formation, exposure, and treatment of DBPs in the context of SPWs. This paper specifically discussed DBP regulations in different regions, formation mechanisms related with disinfectants, precursors and other various conditions, human exposure assessment reflected by biomarkers or epidemiological evidence, and the control and treatment of DBPs. Compared to drinking water with natural organic matter as the main organic precursor of DBPs, the additional human inputs (i.e., body fluids and personal care products) to SPWs make the water matrix more complicated and lead to the formation of more types and greater concentrations of DBPs. Dermal absorption and inhalation are two main exposure pathways for trihalomethanes while ingestion for haloacetic acids, reflected by DBP occurrence in human matrices including exhaled air, urine, blood, and plasma. Studies show that membrane filtration, advanced oxidation processes, biodegradation, thermal degradation, chemical reduction, and some hybrid processes are the potential DBP treatment technologies. The removal efficiency, possible mechanisms and future challenges of these DBP treatment methods are summarized in this review, which may facilitate their full-scale applications and provide potential directions for further research extension.
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•Body fluid and personal care products are important precursors to DBPs in pool water.•Human exposure to DBPs in swimming pool waters is assessed.•Trihalomethanes are exposed by dermal absorption and inhalation and haloacetic acids by ingestion.•DBP treatment methods, mechanisms and efficiency, and challenges are summarized.
The non-condensable pyrolysis gas from plastic pyrolysis is a suitable fuel and precursor for chemical synthesis. Depending on downstream applications, the selective removal of unsaturated ...hydrocarbons and HCl released from polyvinyl chloride (PVC) is required. This study investigated the selective decomposition of unsaturated hydrocarbons with simultaneous dechlorination of non-condensable pyrolysis gas using a catalytic sorbent containing 5% NiO loaded on CaCO3 support (Ni-Ca) and pristine CaCO3 (Ca) at different temperatures, doses of catalytic sorbent and HCl contents. As a result, Ca removed 98.8% of HCl and decomposed 89% of alkynes and 23% of dienes at 700°C. When applying Ni-Ca, the HCl removal was above 99% at all studied temperatures, while 90% decomposition of alkenes, dienes and alkynes was achieved, depending on temperature, Ni-Ca dose and HCl content. The higher HCl content in gas (43mg against 13mg) negatively influenced the catalytic activity of Ni-Ca, while increasing the selectivity towards the decomposition of alkenes, dienes and alkynes compared to alkanes. At 700°C, 99.6% removal of unsaturated hydrocarbons by Ni-Ca was attained at only 10.1% conversion of alkanes. Thus, depending on the applied catalytic sorbent, either selective decomposition of alkynes and dienes (over Ca) or a mixture of unsaturated hydrocarbons (over Ni-Ca) was achieved with the simultaneous HCl removal from non-condensable pyrolysis gas.
•Upgrading of non-condensable pyrolysis gas from mixed plastics was investigated.•HCl removal and hydrocarbon decomposition over Ni-Ca catalytic sorbent•Higher HCl content in gas decreased catalytic activity of Ni-Ca.•Higher HCl content increased selective decomposition of unsaturated hydrocarbons.•Product gas was similar to some reformate fuels utilized in solid oxide fuel cells.
•Seawater and brine enable struvite formation from source-separated hydrolyzed urine.•Modified chemical equilibrium model agrees with experimental results.•Struvite from synthetic and real urine have ...feather and coffin shape, respectively.•Co-precipitates magnesium-calcite and calcite compromise induced struvite purity.
Struvite (MgNH4PO4·6H2O) precipitation is widely used for nutrient recovery from source-separated urine in view of limited natural resources. Spontaneous struvite formation depletes the magnesium in hydrolyzed urine so that additional magnesium source is required to produce induced struvite for P-recovery. The present study investigated the morphology and purity of induced struvite crystals obtained from hydrolyzed urine by using seawater and desalination brine as low cost magnesium sources. The results demonstrated that both seawater and brine were effective magnesium sources to recover phosphorus from hydrolyzed urine. Crystals obtained from synthetic and real urine were revealed that the morphology was feather and coffin shape, respectively. Structural characterization of the precipitates confirmed that crystallized struvite was the main product. However, co-precipitates magnesium calcite and calcite were observed when seawater was added into synthetic and real urine, respectively. It was found that the presence of calcium in the magnesium sources could compromise struvite purity. Higher struvite purity could be obtained with higher Mg/Ca ratio in the magnesium source. Comparative analysis indicated that seawater and brine had similar effect on the crystallized struvite purity.
Municipal solid waste incineration (MSWI) bottom ash has gained increasing attentions for its friendly application worldwide, due to promotion of waste recycling. One of the biggest concerns for ...incineration bottom ash (IBA) utilization lies in its elevated metal concentrations and leaching potential. While challenges faced by the user are miscellaneous based on several aspects—regulations and rules, the heterogeneity of IBA sources, specific risks arisen from individual applications and/or mixed public views, etc. Extensive knowledge on IBA characterization, existing treatment and application contributes to optimize life cycle of the bottom ash, herein enhancing the IBA management practices. On the understanding that both feedstock and the process for incineration are various, properties, treatments and applications of the IBA are accordingly different. Nevertheless, literature reviewed data indicate evidently that IBA, varying in its original resources and treatment facilities though, shares common geotechnical and chemical properties. As the technology development on the IBA is dominated by these common properties, through which the proper treatment and application could be well determined. In this review three perspectives were concentrated. First, general properties of IBA e.g. heavy metals and their leaching potential, bulk components, particle size distribution and pH were investigated, whereby the general trends were indicated with collective plots. Secondly, the existing status quo on IBA treatment methods and applications were investigated, suggesting a highest potential as low-strength aggregates. Thirdly, toxicity studies and LCA on IBA as emerging research topics were also investigated, to further justify its application feasibility.
•Carbon nanomaterials were synthesized at 500 and 800°C.•Pyrolysis gas decomposed to intermediates prior to catalytic deposition at 800°C.•Carbon properties were influenced by feedstock at lower ...synthesis temperature.•PET in plastic mixture suppressed catalytic activity at 500°C.
The conversion of non-condensable pyrolysis gases from plastic feedstock into carbon nanomaterials through catalytic chemical vapor deposition was investigated. Three samples, namely low density polyethylene (LDPE), polypropylene (PP) and a mixture of four plastics (MP), containing LDPE (40%), PP (40%), polystyrene (PS) (10%) and polyethylene terephthalate (PET) (10%), were used as raw materials in the pyrolysis process. The plastics were initially pyrolyzed at 600°C producing condensable oils and non-condensable gases. The non-condensable gases were further heated in the second reactor either at 500 or 800°C. Heating at 800°C caused decomposition of the gases to intermediate products (methane, ethylene and condensable oils), which were converted over a nickel-based catalyst into multi-walled carbon nanotubes with similar yields and properties regardless of the plastic feedstock. Heating at 500°C had no effect on the composition of non-condensable pyrolysis gases. However, the carbon materials produced over the catalyst had different yields and structures implying the influence of plastic feedstock on the properties of materials was more pronounced at lower synthesis temperature. At 500°C, the MP non-condensable pyrolysis gases were converted into a mixture of carbon nanocages and multi-walled carbon nanotubes with higher graphitization degree compared to carbon materials from PP and LDPE, which were mainly multi-walled carbon nanotubes. Furthermore, the carbon yield was the highest using PP followed by LDPE and MP samples (32%, 21% and 3%, respectively). The lower carbon yield using LDPE compared to PP was attributed to the lower concentration of unsaturated hydrocarbons in the pyrolysis gas, while the low yield using MP was caused by the presence of PET in the plastic mixture, decreasing the reactivity of hydrocarbon gases over the catalyst.
A novel anaerobic osmotic membrane bioreactor (AnOMBR) was developed for treating low-strength wastewater. The AnOMBR utilizes a forward osmosis (FO) membrane to retain influent organic waste, which ...facilitates anaerobic wastewater treatment and energy recovery in the form of methane gas. The feasibility of AnOMBR for treating low-strength wastewater at mesophilic temperature was evaluated and membrane fouling was investigated. Permeate flux declined under the combined effects of both salt accumulation and membrane fouling. Although flux reduction was dominated by the effect of salt accumulation in the reactor, the presence of organic fouling and inorganic scaling could be clearly identified. Bulk pH could be maintained within neutral to slightly alkaline due to the retention of alkalinity by the FO membrane. The AnOMBR shows good and stable removal of soluble chemical oxygen demand (sCOD) and nearly complete removal of total phosphorous. However, only partial removal of total nitrogen and ammonia was observed. The elevated salt environment appeared to have little effect on bioactivity of methanogens, and stable methane production of 0.3L/g sCOD digested was obtained.
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•A mesophilic anaerobic osmosis membrane bioreactor (AnOMBR) was developed.•The AnOMBR remained biologically active at high salinity level.•Stable and high methane production rate was achieved.•AnOMBR can potentially recover both water and energy from dilute wastewater.
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