A linear matrix inequality (LMI) approach to robust H2 sampled-data control for linear uncertain systems

In this paper, we consider the H2 sampled-data control for uncertain linear systems by the impulse response interpretation of the H2 norm. Two H2 measures for sampled-data systems are considered. The robust optimal control procedures subject to these two H2 criteria are proposed. The development is primarily concerned with a multirate treatment in which a periodic time-varying robust optimal control for uncertain linear systems is presented. To facilitate multirate control design, a new result of stability of hybrid system is established. Moreover, the single-rate case is also obtained as a special case. The sampling period is explicitly involved in the result which is superior to traditional methods. The solution procedures proposed in this paper are formulated as an optimization problem subject to linear matrix inequalities. Finally, we present a numerical example to demonstrate the proposed techniques.published_or_final_versio

Dynamic membrane bioreactor performance enhancement by powdered activated carbon addition: Evaluation of sludge morphological, aggregative and microbial properties

© 2018 The effects of powdered activated carbon (PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor (DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane (DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes (protists and metazoans) and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC (BPAC), which promoted the enrichment of Acinetobacter (13.9%), Comamonas (2.9%), Flavobacterium (0.31%) and Pseudomonas (0.62%), all contributing to sludge flocs formation and several (such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance

Dynamic membrane-assisted fermentation of food wastes for enhancing lactic acid production

© 2017 Elsevier Ltd A dynamic membrane (DM) module was inserted into a fermentation reactor to separate soluble products from the fermented mixture to increase lactic acid (LA) production from food wastes under acidogenic conditions (uncontrolled pH, pH 4 and 5). With a high total suspended solid content (20–40 g/L) in the fermenter, a stable DM could be maintained through regular backwashing. By effectively intercepting suspended solids and lactic acid bacteria (LAB), the fermenter was able to increase microbial activity and largely promote LA yield. Hydrolysis and acidogenesis rates increased with pH, and the highest LA yield (as high as 0.57 g/g-TS) was obtained at pH 4. The microbial community analysis showed that the relative abundance of Lactobacillus increased to 96.4% at pH 4, but decreased to 43.3% at pH 5. In addition, the DM could be easily recovered by intercepting larger particles in less than 2 h after each cycle of periodic backwashing

Roles of sponge sizes and membrane types in a single stage sponge-submerged membrane bioreactor for improving nutrient removal from wastewater for reuse

Sponge not only can reduce membrane fouling by means of mechanical cleaning and maintain a balance of suspended-attached microorganisms in submerged membrane bioreactor (SMBR), but also can enhance dissolved organic matter and nutrient removal. This study investigated the performance of three different sizes of sponge (S28-30/45R, S28-30/60R and S28-30/90R) associated with continuous aerated SMBR. A laboratory-scale single stage sponge-SMBR (SSMBR) showed high performance for removing dissolved organic matter (>96%) and PO4-P (>98.8), while coarse sponges such as S28-30/45R, S28-30/60R could achieve more than 99% removal of NH4-N. When three-size sponges (S28-30/45R, S28-30/60R and S28-30/90R) were mixed at a ratio of 1:1:1 and in conjunction with two kinds of membranes (0.1 μm hollow fiber and 2 μm nonwoven), the SSMBR system has proved its generic merits of superior treated effluent quality and less membrane fouling. The NH4-N and PO4-P removal were found excellent, which were more than 99.8% and over 99% respectively. Molecular weight distribution also indicated that major fractions of organic matter could be successfully removed by SSMBR. © 2009 Elsevier B.V. All rights reserved

Applying fermentation liquid of food waste as carbon source to a pilot-scale anoxic/oxic-membrane bioreactor for enhancing nitrogen removal: Microbial communities and membrane fouling behaviour

© 2017 Elsevier Ltd Fermentation liquid of food waste (FLFW) was applied as an external carbon source in a pilot-scale anoxic/oxic-membrane bioreactor (A/O-MBR) system to enhance nitrogen removal for treating low COD/TN ratio domestic wastewater. Results showed that, with the FLFW addition, total nitrogen removal increased from lower than 20% to 44–67% during the 150 days of operation. The bacterial metabolic activities were obviously enhanced, and the significant change in microbial community structure promoted pollutants removal and favored membrane fouling mitigation. By monitoring transmembrane pressure and characterizing typical membrane foulants, such as extracellular polymeric substances (EPS), dissolved organic matter (DOM), and inorganics and biopolymers in the cake layer, it was confirmed that FLFW addition did not bring about any additional accumulation of membrane foulants, acceleration of fouling rate, or obvious irreversible membrane fouling in the whole operation period. Therefore, FLFW is a promising alternative carbon source to enhance nitrogen removal for the A/O-MBR system

Use of magnetic powder to effectively improve the performance of sequencing batch reactors (SBRs) in municipal wastewater treatment

© 2017 Elsevier Ltd This study aims to investigate the effect of adding magnetic powder in the sequencing batch reactor (SBR) on the reactor performance and microbial community. Results indicated that, the magnetic activated sludge sequencing batch reactor (MAS-SBR) had 7.76% and 4.76% higher ammonia nitrogen (NH4+-N) and chemical oxygen demand (COD) removal efficiencies than that of the conventional SBR (C-SBR). The MAS-SBR also achieved 6.86% sludge reduction compared with the C-SBR. High-throughput sequencing demonstrated that the dominant phyla of both SBRs (present as ≥1% of the sequence reads) were Protebacteria, Bacteroidetes, Chloroflexi, Saccharibacteria, Chlorobi, Firmicutes, Actinobactoria, Acidobacteria, Planctomycetes and unclassified_Bacteria. The relative abundance of Protebacteria and Bacteroidetes simultaneously declined whereas the other 8 phyla increased following the addition of magnetic powder. Adding magnetic powder in the SBR significantly affected the microbial diversity and richness of activated sludge, consequently affecting the reactor performance

A high sensitivity iron-dependent bioreporter used to measure iron bioavailability in freshwaters

A Nostoc sp. PCC 7120 iron bioreporter containing iron-regulated schizokinen transporter gene alr0397 promoter fused to the luxAB genes was examined to optimize its response to bioavailable iron. Doseresponse relationships between luciferase activity and free ferric ion (Fe3+) concentrations pFe (-lg [Fe3+]) were generated by measuring luciferase activities of the bioreporter in trace metalbuffered Fraquil medium with various incubation times. The results were best demonstrated by sigmoidal curves (pFe 18.821.7, Fe3+ = 10-18.810-21.7 M) with the linear range extending from pFe 19.621.5 (Fe3+ = 10-19.610-21.5 M) after a 12-h incubation time. Optimal conditions for the use of this bioreporter to sense the iron bioavailability were determined to be: a 12-h exposure time, initial cell density of OD730 nm = 0.06, high nitrate (100 mu M), high phosphate (10 mu M), moderate Co2+ (0.122.5 nM), Zn2+ (0.1612 nM), Cu2+ (0.0450 nM), and wide range of Mn2+ concentration (0.922300 nM). The applicability of using this iron bioreporter to assess iron availability in the natural environment has been tested using water samples from eutrophic Taihu, Donghu, and Chaohu lakes. It is indicated that the bioreporter is a useful tool to assess bioavailable iron in various water quality samples, especially in eutrophic lakes with high bioavailable iron.A Nostoc sp. PCC 7120 iron bioreporter containing iron-regulated schizokinen transporter gene alr0397 promoter fused to the luxAB genes was examined to optimize its response to bioavailable iron. Doseresponse relationships between luciferase activity and free ferric ion (Fe3+) concentrations pFe (-lg [Fe3+]) were generated by measuring luciferase activities of the bioreporter in trace metalbuffered Fraquil medium with various incubation times. The results were best demonstrated by sigmoidal curves (pFe 18.821.7, Fe3+ = 10-18.810-21.7 M) with the linear range extending from pFe 19.621.5 (Fe3+ = 10-19.610-21.5 M) after a 12-h incubation time. Optimal conditions for the use of this bioreporter to sense the iron bioavailability were determined to be: a 12-h exposure time, initial cell density of OD730 nm = 0.06, high nitrate (100 mu M), high phosphate (10 mu M), moderate Co2+ (0.122.5 nM), Zn2+ (0.1612 nM), Cu2+ (0.0450 nM), and wide range of Mn2+ concentration (0.922300 nM). The applicability of using this iron bioreporter to assess iron availability in the natural environment has been tested using water samples from eutrophic Taihu, Donghu, and Chaohu lakes. It is indicated that the bioreporter is a useful tool to assess bioavailable iron in various water quality samples, especially in eutrophic lakes with high bioavailable iron

Optimization of organics and nitrogen removal in intermittently aerated vertical flow constructed wetlands: Effects of aeration time and aeration rate

© 2016 Elsevier Ltd In this study, to optimize aeration for the enhancement of organics and nitrogen removal in intermittently aerated vertical flow constructed wetlands (VF CWs) for treating domestic wastewater, the experimental VF CWs were operated at different aeration time (1 h d−1, 2 h d−1, 4 h d−1, 6 h d−1, 8 h d−1 and 10 h d−1) and aeration rate (0.1 L min−1, 0.2 L min−1, 0.5 L min−1, 1.0 L min−1 and 2.0 L min−1) to investigate the effect of artificial aeration on the removal efficiency of organics and nitrogen. The results showed that the optimal aeration time and aeration rate were 4 h d−1 and 1.0 L min−1, which could create the appropriate aerobic and anoxic regions in CWs with the greater removal of COD (97.2%), NH4+-N (98.4%) and TN (90.6%) achieved simultaneously during the experiment. The results demonstrate that the optimized intermittent aeration is reliable option to enhance the treatment performance of organics and nitrogen at a lower operating cost

Characterization of a hybrid powdered activated carbon-dynamic membrane bioreactor (PAC-DMBR) process with high flux by gravity flow: Operational performance and sludge properties

© 2016 Elsevier Ltd Three PAC-DMBRs were developed for wastewater treatment under different PAC dosages with biomass concentrations averaged at 2.5, 3.5 and 5.0 g/L. The DMBRs could be continuously operated at 40–100 L/m2 h, while higher fluxes were obtained within the PAC-DMBRs with hydraulic retention times varying in 4–10 h. A dose of 1 g/L PAC brought about obvious improvement in the sludge particle size distribution, settling, flocculating and dewatering properties due to the formation of biological PAC, and the sludge properties were further improved at a higher PAC dose (3 g/L). The addition of PAC notably shortened the DM formation time after air backwashing and enhanced pollutant removal. Moreover, under a long solid retention time (approximately 150 d), the concentrations of both soluble and bound extracellular polymeric substances (EPS) decreased substantially because of the adsorption and biodegradation effects of the biological PAC. No obvious impact on biomass activity was observed with PAC addition

Simultaneous improvement of waste gas purification and nitrogen removal using a novel aerated vertical flow constructed wetland

© 2017 Elsevier Ltd Insufficient oxygen supply is identified as one of the major factors limiting organic pollutant and nitrogen (N) removal in constructed wetlands (CWs). This study designed a novel aerated vertical flow constructed wetland (VFCW) using waste gas from biological wastewater treatment systems to improve pollutant removal in CWs, its potential in purifying waste gas was also identified. Compared with unaerated VFCW, the introduction of waste gas significantly improved NH4+-N and TN removal efficiencies by 128.48 ± 3.13% and 59.09 ± 2.26%, respectively. Furthermore, the waste gas ingredients, including H2S, NH3, greenhouse gas (N2O) and microbial aerosols, were remarkably reduced after passing through the VFCW. The removal efficiencies of H2S, NH3 and N2O were 77.78 ± 3.46%, 52.17 ± 2.53%, and 87.40 ± 3.89%, respectively. In addition, the bacterial and fungal aerosols in waste gas were effectively removed with removal efficiencies of 42.72 ± 3.21% and 47.89 ± 2.82%, respectively. Microbial analysis results revealed that the high microbial community abundance in the VFCW, caused by the introduction of waste gas from the sequencing batch reactor (SBR), led to its optimized nitrogen transformation processes. These results suggested that the VFCW intermittently aerated with waste gas may have potential application for purifying wastewater treatment plant effluent and waste gas, simultaneously