Moistube irrigation fouling due to anaerobic filtered effluent (AF) and horizontal flow constructed wetland (HFCW) effluent.
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ABSTRACT: The study assessed the suitability of two effluent types, namely anaerobic filtered (AF) and horizontal flow constructed wetland (HFCW) effluent for Moistube irrigation (MTI). Secondary to this, the study determined the plugging coefficients (α) on MTI for the respective effluents. The feed water was supplied from a raised tank (3.5 m), and mass-flow rates were recorded at 15 min intervals using an electronic balance. The effluent feed water concentrations and experimental room temperature (25 °C ± 1 °C) were continuously monitored and kept constant. Hermia's models based on the [Formula: see text] coefficient was used to select the best fitting fouling mechanism model and, consequently, the plugging coefficients. In addition, microbial colony analysis and scanning electron microscopy (SEM) analysis was carried out to assess the composition of the deposited sediment (DS) and adhered bacterial film (ABF) onto the MTI lateral. The study revealed that MTI pore blocking was a complex phenomenon described by complete pore-blocking model ([Formula: see text] ≥ 0.50). Discharge followed an exponential decay with early fouling observed on AF effluent because of a high concentration of total suspended solids (TSS) and dissolved organic matter (DOM). Discharge declined by 50% after 20 and 10 h of intermittent operation for AF and HFCW effluent, respectively. The α for each effluent (foulant) were [Formula: see text] = 0.07 and [Formula: see text] = 0.05, respectively, for AF and HFCW. The microbial analysis revealed bacterial aggregation structures that contributed to pore blocking. SEM imaging revealed complete surface coverage by deposited sediment. It is concluded that water quality determines the operation life span of MTI, and the two effluents promote accelerated MTI pore fouling or blocking. Continuous use without flushing the MTI will promote membrane degradation and reduced discharge efficiency. Additional filtration can potentially mitigate the membrane degradation process.
Project description:Data-driven approaches that make timely predictions about pollutant concentrations in the effluent of constructed wetlands are essential for improving the treatment performance of constructed wetlands. However, the effect of the meteorological condition and flow changes in a real scenario are generally neglected in water quality prediction. To address this problem, in this study, we propose an approach based on multi-source data fusion that considers the following indicators: water quality indicators, water quantity indicators, and meteorological indicators. In this study, we establish four representative methods to simultaneously predict the concentrations of three representative pollutants in the effluent of a practical large-scale constructed wetland: (1) multiple linear regression; (2) backpropagation neural network (BPNN); (3) genetic algorithm combined with the BPNN to solve the local minima problem; and (4) long short-term memory (LSTM) neural network to consider the influence of past results on the present. The results suggest that the LSTM-predicting model performed considerably better than the other deep neural network-based model or linear method, with a satisfactory R2. Additionally, given the huge fluctuation of different pollutant concentrations in the effluent, we used a moving average method to smooth the original data, which successfully improved the accuracy of traditional neural networks and hybrid neural networks. The results of this study indicate that the hybrid modeling concept that combines intelligent and scientific data preprocessing methods with deep learning algorithms is a feasible approach for forecasting water quality in the effluent of actual engineering. Graphical abstract Image 1 Highlights • Four prediction models are successfully established through multisource data fusion.• The LSTM shows a satisfactory forecast accuracy.• The moving average method can obviously improve the accuracy of the GA-BPNN.
Project description:Constructed wetlands have been recognized as a removal treatment option for high concentrations of contaminants in agricultural waste before land application. The goal of this study was to characterize microbial composition in two constructed wetlands designed to remove contaminants from dairy washwater. Water samples were collected weekly for 11 months from two wetlands to determine the efficiency of the treatment system in removal of chemical contaminants and total and fecal coliforms. The reduction by the treatment was greatest for biological oxygen demand, suspended solids, chemical oxygen demand, nitrate, and coliforms. There was only moderate removal of total nitrogen and phosphorus. Changes in the total bacterial community and ammonia-oxidizing bacterial composition were examined by using denaturing gradient gel electrophoresis (DGGE) and sequencing of PCR-amplified fragments of the gene carrying the alpha subunit of the ammonia monooxygenase gene (amoA) recovered from soil samples and DGGE bands. DGGE analysis of wetlands and manure samples revealed that the total bacterial community composition was dominated by bacteria from phylogenetic clusters related to Bacillus, Clostridium, Mycoplasma, Eubacterium, and Proteobacteria originally retrieved from the gastrointestinal tracts of mammals. The population of ammonia-oxidizing bacteria showed a higher percentage of Nitrosospira-like sequences from the wetland samples, while a higher percentage of Nitrosomonas-like sequences from manure, feces, raw washwater, and facultative pond was found. These results show that the wetland system is a natural process dependent upon the development of healthy microbial communities for optimal wastewater treatment.
Project description:In the coming years, water stress is destined to worsen considering that the consumption of water is expected to increase significantly, and climate change is expected to become more evident. Greywater (GW) has been studied as an alternative water source in arid and semiarid zones. Although there is no single optimal solution in order to treat GW, constructed wetlands proved to be effective. In this paper, the results of the treatment of a real GW by a horizontal flow constructed wetland (HFCW) for more than four months are shown. In the preliminary laboratory-scale plant, Phragmites australis, Carex oshimensis and Cyperus papyrus were tested separately and showed very similar results. In the second phase, pilot-scale tests were conducted to confirm the performance at a larger scale and evaluate the influence of hydraulic retention time, obtaining very high removal yields on turbidity (>92%), total suspended solids (TSS) (>85%), chemical oxygen demand (COD) (>89%), and five-day biological oxygen demand (BOD5) (>88%). Based on the results of the pilot-scale HFCW, a comparison with international recommendations by World Health Organization and European Union is discussed.
Project description:Previously, Planted Fixed-Bed Reactors (PFRs) have been used to investigate microbial toluene removal in the rhizosphere of constructed wetlands. Aerobic toluene degradation was predominant in these model systems although bulk redox conditions were hypoxic to anoxic. However, culture-independent approaches indicated also that microbes capable of anaerobic toluene degradation were abundant. Therefore, we aimed at isolating anaerobic-toluene degraders from one of these PFRs. From the obtained colonies which consisted of spirilli-shaped bacteria, a strain designated 15-1 was selected for further investigations. Analysis of its 16S rRNA gene revealed greatest similarity (99%) with toluene-degrading Magnetospirillum sp. TS-6. Isolate 15-1 grew with up to 0.5 mM of toluene under nitrate-reducing conditions. Cells reacted to higher concentrations of toluene by an increase in the degree of saturation of their membrane fatty acids. Strain 15-1 contained key genes for the anaerobic degradation of toluene via benzylsuccinate and subsequently the benzoyl-CoA pathway, namely bssA, encoding for the alpha subunit of benzylsuccinate synthase, bcrC for subunit C of benzoyl-CoA reductase and bamA for 6-oxocyclohex-1-ene-1-carbonyl-CoA hydrolase. Finally, most members of a clone library of bssA generated from the PFR had highest similarity to bssA from strain 15-1. Our study provides insights about the physiological capacities of a strain of Magnetospirillum isolated from a planted system where active rhizoremediation of toluene is taking place.
Project description:Membrane fouling is a considerable challenge for the stable operation of anaerobic membrane-based bioreactors. Membrane used as a cathode is a common measure to retard fouling growth in anaerobic electrochemical membrane bioreactors (AnEMBR), which; however, cannot avoid the fouling growth. Here we report a strategy using the membrane as an anode to resist membrane fouling in an AnEMBR. Although aggravating in the initial stage, the fouling on the anode membrane is gradually alleviated by the anode oxidation with enriching exoelectrogens to finally achieve a dynamic equilibrium between fouling growth and decomposition to maintain the operation stable. A mesh-like biofilter layer composed of cells with less extracellular polymeric substance (EPS) is formed on the membrane surface to lower the trans-membrane pressure and promote the interception of the anode membrane. The membrane has high electron storage and transfer capacities to accelerate the oxidation of the intercepted fouling materials, especially, the redundant EPSs of the biofilter layer.
Project description:Wetlands have been used to treat anthropogenic effluents for decades due to their intense biogeochemical processes that transform and uptake nutrients, organic matter, and toxins. Despite these known functions, we lack generalizable knowledge of effluent-derived dissolved organic matter (DOM) cycling in wetlands. Here, we quantify the cycling of DOM in one of Canada's more economically important wetland complexes (Frank Lake, Alberta), restored to hydrologic permanence in the 1980s using urban and agro-industrial effluents. Optical analyses and PARAFAC (parallel factor analysis) modelling showed a clear compositional change from more bioavailable and protein-like DOM at effluent input sites to more aromatic and humic-like at the wetland outflow, likely due to DOM processing and inputs from marsh plants and wetland soils. Microbial incubations showed that effluent DOM was rapidly consumed, with the half-life of DOM increasing from as low as 35 days for effluent, to 462 days at the outflow, as a function of compositional shifts toward aromatic, humic-like material. Long-term averaged dissolved organic carbon (DOC) export was low compared to many wetlands (10.3 ± 2.0 g C m-2 yr-1). Consistent with predictions based on water residence time, our mass balance showed Frank Lake was a net source of DOM across all measured years, but shifted from a source to sink among wet and drought years that respectively shortened or lengthened the water residence and DOM processing times. Overall, Frank Lake processes and transforms effluent DOM, despite being a longer-term net source of DOM to downstream environments.Supplementary informationThe online version contains supplementary material available at 10.1007/s10533-022-01002-x.
Project description:Anaerobic ammonium-oxidizing (anammox) bacteria, aerobic ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB) are three groups of ammonium/ammonia-oxidizing prokaryotes (AOPs) that are involved in the nitrogen cycle. This research compared the AOP communities in a constructed freshwater wetland with a natural coastal marine wetland in the subtropical Hong Kong. Both vegetated/rhizosphere and nonvegetated sediments were investigated to identify the effects of different macrophytes on the AOP communities. The polymerase chain reaction (PCR)-amplified gene fragments of 16S rRNA and archaeal and bacterial amoA (encoding the ammonia monooxygenase alpha subunit) were applied as molecular biomarkers to analyze the AOPs' phylogeny and diversity. Quantitative PCR was used to determine the abundances of AOPs in the sediments. The results showed that the relatively more heterogeneous freshwater wetland contained a broader range of phylotypes, higher diversity, more complex community structures, and more unevenly distributed abundances of AOPs than the coastal wetland. The effects of vegetation on the community structures of AOPs were plant-specific. The exotic Typha angustifolia affected the community structures of all AOPs and enhanced their abundances in the rhizosphere region. Both Phragmites australis and Cyperus malaccensis showed some effects on the community structures of AOB, but minimal effects on those of anammox bacteria or AOA. Kandelia obovata had almost no detectable effect on all AOPs due to their smaller size. This study suggested that the freshwater and coastal marine wetlands may have different contributions to the inorganic N removal due to the variations in AOP communities and plant types.
Project description:Removal of nitrogen (N) is a critical aspect in the functioning of constructed wetlands (CWs), and the N treatment in CWs depends largely on the presence and activity of macrophytes and microorganisms. However, the effects of plants on microorganisms responsible for N removal are poorly understood. In this study, a three-stage surface flow CW was constructed in a pilot-scale within monospecies stands of Myriophyllum aquaticum to treat swine wastewater. Steady-state conditions were achieved throughout the 600-day operating period, and a high (98.3%) average ammonia removal efficiency under a N loading rate of 9 kg ha-1 d-1 was observed. To determine whether this high efficiency was associated with the performance of active microbes, the abundance, structure, and interactions of microbial community were compared in the unvegetated and vegetated samples. Real-time quantitative polymerase chain reactions showed the abundances of nitrifying genes (archaeal and bacterial amoA) and denitrifying genes (nirS, nirK, and nosZ) were increased significantly by M. aquaticum in the sediments, and the strongest effects were observed for the archaeal amoA (218-fold) and nirS genes (4620-fold). High-throughput sequencing of microbial 16S rRNA gene amplicons showed that M. aquaticum greatly changed the microbial community, and ammonium oxidizers (Nitrosospira and Nitrososphaera), nitrite-oxidizing bacteria (Nitrospira), and abundant denitrifiers including Rhodoplanes, Bradyrhizobium, and Hyphomicrobium, were enriched significantly in the sediments. The results of a canonical correspondence analysis and Mantle tests indicated that M. aquaticum may shift the sediment microbial community by changing the sediment chemical properties. The enriched nitrifiers and denitrifiers were distributed widely in the vegetated sediments, showing positive ecological associations among themselves and other bacteria based on phylogenetic molecular ecological networks.