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With the rapid development and application of consumer products containing nanoparticles (NPs), especially titanium dioxide (TiO2) NPs, the potential effects of suspended NPs on wastewater treatment has been a concern over the recent years. This study investigated the potential effects of suspended TiO2 NPs on activated sludge flocculation properties in a membrane bioreactor (MBR). Results showed that suspended TiO2 NPs inhibited the viability of activated sludge flocs, and led to bacterial protein secretion for bacterial protection, causing an overall protein increase of soluble microbial products. Suspended TiO2 NPs also destabilized the activated sludge floc structure and reduced flocculation capacity of flocs, causing an over production of organic matter and resulting in a floc size decrease of over 50%. Suspended TiO2 NPs also caused a change in the phylogenetic distribution of bacterial community. Whereby, the dominant species in activated sludge was replaced from Comamonadaceae to Thiotrichaceae in 50 mg/L suspended TiO2 NPs.

The response of microbial communities to continual and prolonged water exposure provides useful insight when facing global climate changes that cause increased and uneven precipitation and extreme rainfall events. In this study, we investigated an in situ manipulative experiment with four levels of water exposure (ambient precipitation +0%, +25%, +50%, and +100% of local annual mean precipitation) in a desert ecosystem of China. After 9 years of water addition, Illumina sequencing was used to analyze taxonomic compositions of the soil bacterial, archaeal, and fungal communities. The results showed significant increases in microbial biomass carbon (MBC) at higher amended precipitation levels, with the highest values reported at 100% precipitation. Furthermore, an increase in the bacterial species richness was observed along the water addition gradient. In addition, the relative abundance of several bacterial phyla, such as Proteobacteria, significantly increased, whereas that of some drought-tolerant taxa, including Actinobacteria, Firmicutes, and Bacteroidetes, decreased. In addition, the phyla Planctomycetes and Nitrospirae, associated with nitrification, positively responded to increased precipitation. Archaeal diversity significantly reduced under 100% treatment, with changes in the relative abundance of Thaumarchaeota and Euryarchaeota being the main contributors to shifts in the archaeal community. The fungal community composition was stable in response to water addition. Results from the Mantel test and structural equation models suggested that bacterial and archaeal communities reacted contrastingly to water addition. Bacterial community composition was directly affected by changing soil moisture and temperature, while archaeal community composition was indirectly affected by changing nitrogen availability. These findings highlight the importance of soil moisture and nitrogen in driving microbial responses to long-term precipitation changes in the desert ecosystem.

Radio frequency identification (RFID) technology has been widely used in various industries due to its object identification and monitoring capability. In recent years, low-frequency (LF) RFID has been increasingly used in hydraulic studies for sediment transport studies and the detection of underground utilities. Nevertheless, prior studies have indicated that the use of LF RFID technology is limited due to its short detection range and high sensitivity of orientation relative to the antenna place. Ultra-high frequency (UHF) RFID (865-928 MHz) technology has much longer reading ranges compared to the LF RFID. However, up to date, the application of UHF RFID technology in aquatic environments is still rare because of its high sensitivity to water. This study aims to investigate the reading range behaviors of passive UHF RFID tags for surface applications in aquatic environments. This research used circular and linear polarization antennae, which have a gain of 8 dBic, 9 dBic, and 12.5 dBi, respectively, to examine six pre-selected UHF RFID tags behaviors. The results of this study showed that a decrease in the performance of maximum reading distances when the tags are placed in a vertical orientation at the center of the antenna compared with the horizontal orientation. The maximum reading ranges varied between 1 to 35% when using the 8 dBic antenna, between 0% to 48% with the 9 dBic antenna, and between 14 to 82% with the 12.5 dBi antenna. Based on key findings and observations from this study, we demonstrated design requirements of tags to overcome sensitivity limitations to design for future surface-water velocity monitoring applications in the natural open water and built water transport environments.

Anaerobic ammonium oxidation (anammox)-based nitrogen removal saves aeration energy and organic carbon costs, attributed to its anaerobic and autotrophic nature. However, due to the slow growth of anaerobic ammonium oxidation bacteria (AnAOB), drawbacks including long startup time and sensitivity to toxins still hamper the application of anammox-based processes. To cope with the slow growth of AnAOB, various bioreactor configurations have been investigated for the capability of retaining anammox biomass, among which, the expanded granular sludge bed (EGSB) reactor is a promising option. In this study, two laboratory-scale EGSB reactors were used to gain insights of microbial population and their response to amending biofilm-carriers, aiming to enhance the biomass retention of AnAOB. The respective ammonium and nitrite removal efficiencies were up to over 90%, and the overall nitrogen removal efficiency (NRE) was stable at over 70%, in the EGSB reactor amended with carriers (CEGSB). Compared to the control EGSB, CEGSB's observed performance was more stable during the 236-day operational period. The abundance of AnAOB reached 22% in the EGSB and 49% in the CEGSB. It was also observed that Ca. Brocadia (14.25%) and Asahi BRW2 (33.19%) coexisted in the CEGSB. The dynamics of major metabolisms and functional genes involved in nitrogen conversion were further observed by FAPROTAX based on the taxonomic data, providing more insights into the functions of the microbial communities.

In situ and short-time anaerobic digestion coupled with alkalization and mechanical stirring was studied to enhance sludge (especially high-inorganic sludge) disintegration for phosphate recovery. Anaerobic digestion batch experiments with varying conditions were carried out. It was observed that high initial pH values (e.g. 9, 10, 12 and 13) in conjunction with mechanical stirring resulted in effective sludge disintegration. Results showed that mechanical stirring mainly worked as the role of uniform mixing for better material exchange and bacteria contact, but without the function of vortex shear force for cell wall breaking. Bacterial effects contributed less and less to phosphate recovery from sludge as alkalization increased, indicating that chemical effects have a more significant role during operation. Meanwhile, almost all insoluble non-apatite inorganic phosphorus was dissolved back into the supernatant with alkalization and mechanical stirring. Therefore, compared with other sludge disintegration methods, in situ and short-time anaerobic digestion coupled with alkalization and mechanical stirring is economical and practical, requiring only 7 days for sludge disintegration, especially with optimum alkalinity (pH 9 & 10).

Inorganic characteristics of cake layer in an anoxic/oxic membrane bioreactor (A/O MBR) for anaerobically digested leachate from a municipal solid waste incineration plant with MAP (magnesium ammonium phosphate precipitation) pretreatment was reported. During 90 days of operation, the A/O-MBR had formed a thick cake layer, causing severe fouling. BCR (European Community Bureau of Reference) results showed that Fe, Al, Ca, Mg, Si were the dominant inorganic components (especially residual Si and Al) in the cake layer. X-ray diffraction (XRD) analysis further presented that the cake layer contained complex inorganic substances with FeSiO 3 , CaAl 2 O 3 , Ca 5 (PO 4 ) 3 OH, CaCO 3 , CaPO 3 OH, Mg 2 (PO 4 )OH, etc., while Si-Al crystal was the major inorganic component in the cake layer. Additionally, SEM-EDX showed a consistent distribution of inorganics along the front cross-section of the cake layer, indicating that the stable particles and metal ions led to the steady inorganic accumulation onto the membrane surface. However, it was revealed that high suction pressure aggravated the inorganic particle accumulation, especially for the Si-Al crystals, at the end of the cake layer.

Microbial community in in-situ waste sludge anaerobic digestion with alkalization for enhancement of nutrient recovery and energy generation was studied. Firmicutes, Proteobacteria and Bacteroidetes phylum became the majority in the microbial community, especially Firmicutes showed the predominate role in the community due to its thick cell wall structure, potential ability hydrolysis and hydrogenogenic acidogenesis. Anaerobic digestion with alkalization caused the obvious microbial diversity decrease, and over 50% of minority bacteria grew up in quantity from original sludge. Phylum of Firmicutes developed by themselves having few interactions with other bacteria, partly contributing to its rapid growth in anaerobic digestion with alkalization. The decrease of hydrocarbon degradation, and the increase of both fermentation and reductive acetogenesis in microbial community, indicating the promotion of short chain fatty acids production, especially acetic acid which is the key intermediate products for nutrient recovery and energy generation.

Sanitary and stormwater sewers are buried assets that play important roles in the prevention of diseases and the reduction of health risks for our societies. Due to their hidden nature, these assets are not frequently assessed and maintained to optimal conditions. The lack of maintenance can cause sewer blockages and overflows that result in the release of pathogens into the environment. For cities, monitoring sewer conditions on a large-scale can be costly, time-consuming, and labor-intensive if using current low-throughput technologies, such as dye testing or closed-circuit television. Alternatively, smart sensor systems can provide low-cost, high-throughput, and automatic data-driven features for real-time monitoring applications. In this study, we developed ultrahigh-frequency radio-frequency identification (UHF RFID)-based sensors that are flushable and suitable for sanitary and stormwater pipes quick surveys. 3D printed RFID sensors were designed to float at the water-air interface and minimize the water interference to RF signal communications. The optimal detection range was also determined to support the design and installation of the reader in various utility holes. Field trials demonstrated that the UHF RFID system is a low-cost, high-throughput, and robust solution for monitoring blockage, illicit-connection, and water flow in sewer networks.

In this study, an anoxic-oxic membrane bioreactor (A/O-MBR), was used to treat effluent tannery wastewater pretreated by physicochemical processes. The A/O-MBR performed well during the experimental period and was able to produce a high-quality effluent containing 90 ± 10 mg-CODcr/L and 0.5 ± 0.1 mg-NH4+-N/L. However, it was observed that at rates of approximately 1.02 kPa/day and 1.2 μm/day, both transmembrane pressure (TMP) and thickness of cake layer increased during wastewater treatment. The eventual thickness of the cake layer was between 47.8 and 51.5 μm. Furthermore, an Inductively Coupled Plasma-Optical Emission Spectrometer, used to analyze inorganic components of the cake layer, revealed that four inorganic elements, Cr, Ca, Mg and Al were predominant (weight percentage rate 4:13:10:72). Due to low solubility (Cr(OH)3: Ksp 6.3 × 10−31; Al(OH)3: Ksp 6.3 × 10−19), the elements of Cr and Al mainly existed in the forms of Cr(OH)3 and Al(OH)3, respectively. Other minerals in the cake layer included Al2O3, CaCO3, and MgCO3. Additionally, using an SEM-EDX (Scanning electron microscopy-energy dispersive X-ray analyzer), we discovered that inorganic particles that formed within the activated sludge of the A/O-MBR steadily accumulating on the membrane surface, resulted in an evenly distributed inorganic layer which could be observed along the cross-sections of the cake layer.