Filamentous and non-filamentous bulking of activated sludge encountered under nutrients limitation or deficiency conditions

Although the limitation or deficiency of nutrients, such as nitrogen (N) and phosphorus (P), has been one of the frequently reported factors causing filamentous or non-filamentous bulking of activated sludge, the mechanisms are still unclear. In this work, the long-term effects of N and P limitation or deficiency on sludge settleability and bioflocculation characteristics were investigated in six sequencing batch reactors (SBRs) fed with wastewater with different nutrient availability. The sludge volume index (SVI), microbial community structures, intracellular poly-β-hydroxyalkanoates (PHAs) and extracellular polymeric substances (EPS) were characterised over time. Bulking was not observed in SBRs with N limitation or deficiency, in which SVI remained below 150. mL/g. In contrast, bulking was encountered in those reactors with P deficiency. The occurrence of non-filamentous bulking was associated with a higher carbohydrates fraction and a lower proteins fraction in EPS. In the case of filamentous bulking, SVI correlated negatively with the amount of PHAs. Our experimental data support the hypothesis that the occurrence and/or the type of bulking in activated sludge could be affected by the combination of kinetic selection, microbial storage, as well as the EPS composition

Health Risk Assessment and Influencing Factors Analysis of High Temperatures on Negative Emotions

The emotional health of urban residents has been seriously threatened by frequent and normalized heat waves. This study constructed the VI-level assessment standard for emotional health risk using data from satellite images, meteorological sites, questionnaire surveys, and statistical yearbooks to assess the effect of high temperatures on negative emotions in Hangzhou. The results showed that the morphological changes of urban high-temperature areas were aggregated from a cross-shape to a large patch shape, then dispersed into cracked patch shapes. Additionally, the health risk of daytime negative emotions peaked at the VI-level from 1984 to 2020, and the influence level of the typical period risk increased by 1–2 levels compared with the daytime. Additionally, driven by urban spatial structure policies, the risk pattern of emotional health expanded outward from a single center into multiple centers. The emotional health risk level rose and then descended in urban centers, and the innovation industries drove the variation tendency of hot spots. Furthermore, high educational background, employment, and couples living together were critical variables that could alleviate the emotional health risk to the middle-aged and elderly population. This study aimed to optimize the urban spatial structure and alleviate residents’ emotional health hazards for healthy urban planning

Microstructural, Thermal, and Tensile Characterization of Banana Pseudo-stem Fibers Obtained with Mechanical, Chemical, and Enzyme Extraction

Banana pseudo-stem fibers (BPSFs) have desirable tensile properties. In this study, BPSFs were extracted using mechanical, chemical, and enzymatic methods. The aim was to evaluate the effect of these three extraction methods on the tensile, thermal, and morphological properties of BPSFs. Microstructural analysis showed the presence of structural and arch fibers in banana pseudo-stem (BPS). The average tensile strength and elongation for mechanically, chemically, and enzyme-extracted BPSFs were 210, 333, and 235 MPa, and 0.8%, 1.6%, and 1.4%, respectively. Young’s modulus was enhanced by 19.1% in the mechanically extracted BPSFs compared with that of chemically extracted BPSFs. The morphology of BPSFs was correlated with their tensile properties via scanning electron microscopy (SEM) image analysis. Fourier transform infra-red (FTIR) and X-ray diffraction (XRD) analyses of fibers showed that chemically extracted BPSFs contained less hemicellulose and lignin with a crystallinity index of 61.2%. Chemically extracted BPSFs exhibited enhanced thermal properties over mechanically extracted BPSFs. Mechanically extracted BPSFs demonstrated similar thermal and tensile properties to chemically and enzyme-extracted BPSFs. Thus, mechanically extracted BPSFs could act as highly suitable reinforcing agents in bio-based composite material preparation. Given that mechanical methods need no chemicals and they are environmentally friendly, such techniques have potential applications

On the Existence of a Normal Trimagic Square of Order 16n

The study of magic squares has a long history, and magic squares have been applied to many mathematical fields. In this paper, we give a complete solution to the existence of normal trimagic squares of all orders 16n. In particular, we obtain a unified solution for the normal trimagic square of order 16n for n>3 by means of set partitions, semibimagic squares, Latin squares, and new product construction. Since there exist normal trimagic squares of orders 16, 32, and 48, we prove that there exists a normal trimagic square of order 16n for every positive integer n

Influence of nitrite on sludge settleability under anoxic and aerobic conditions

Three lab-scale automatic control sequencing batch reactors (SBR) were operated by using acetate as the single carbon source, nitrite was dosed to SBR-1 and SBR-2 under anoxic and aerobic conditions, respectively, and SBR 3 was operated as control without dosing. The results show that, the presence of nitrite under anoxic and aerobic conditions would both cause filamentous sludge bulking. A more serious sludge bulking is observed when the nitrite is presented under the anoxic conditions. Nitrite could stimulate the increase of carbohydrates in extracellular polymeric substances, weaken the storage capability of floc-formers and decrease the phosphorous removal efficiency, thus cause the deterioration of sludge settleability. The dominant filaments are both Thiotrix nivea for SBR-1 and SBR-2 when sludge bulking occurred

Control filamentous bulking caused by chlorine-resistant Type 021N bacteria through adding a biocide CTAB

Filamentous bulking sludge due to excessive growth of filamentous bacteria is a serious operational problem in activated sludge plants. The addition of chemicals is one of widespread ways to control filamentous bulking. In this study, filamentous bulking in a continuous activated sludge system was found to be mainly caused by Eikelboom Type 021N filamentous bacteria likely due to low substrate concentration gradients. These Type 021N bacteria were found to be resistant to chlorination, maintaining cell integrity at a dosage of up to 80 mg Cl/gSS. An alternative biocidal agent, cetyltrimethyl ammonium bromide (CTAB), exhibited a much stronger biocidal effect on these filaments, which significantly improved sludge settleability. Type 021N with filamentous index of 5 was selectively killed, but floc-formers recovery their activity after CTAB termination. The study implied that CTAB might have more penetration capacity to cell wall of chlorine-resistant Type 021N bacteria. We therefore suggest the penetration property of filament cell wall should be considered or tested before the selection of biocide type in practice

Stable limited filamentous bulking through keeping the competition between floc-formers and filaments in balance

Limited filamentous bulking (LFB) was proposed to save aeration energy consumption and enhance the capacity of filaments to degrade substrates with low concentrations in activated sludge systems. Operational parameters favorable for maintaining the LFB state were investigated in an anoxic-oxic reactor treating domestic wastewater. The experiments showed that the LFB state would deteriorate with sharply decreasing temperature, reducing substrate gradients or removing anoxic zones. The balance between filaments and floc-formers could be achieved by controlling dissolved oxygen and sludge loading rates to be in optimal ranges. Eikelboom Type 0041 and Candidatus Microthrix parvicella were the filamentous bacteria responsible for the LFB state. However, the excess growth of Eikelboom Type 021N and Sphaerotilus natans were observed when serious bulking occurred under low substrate gradients. It was demonstrated that stable maintenance of LFB for energy saving was feasible by process control and optimization

Effects of traditional Chinese medicines on intestinal bacteria: A review

401-407<span style="font-size:11.0pt;mso-bidi-font-size: 10.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:zh-cn;mso-bidi-language:ar-sa"="" lang="EN-US">Traditional Chinese medicines (TCM) are increasingly used throughout the world for their effective and few side-effects. Though many studies have successfully proved their <span style="font-size:11.0pt;mso-bidi-font-size:10.0pt; font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">therapeutic e<span style="font-size:11.0pt; mso-bidi-font-size:10.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:zh-cn;="" mso-bidi-language:ar-sa"="" lang="EN-US">ffects both in vivo and in vitro, little researches were carried out to evaluate the interactions between TCM and intestinal microflora, which maybe the key point to reveal the beneficial efficacies of TCM. In this review, the adjustment effects of TCM on intestinal microflora published in recent decades were summarized and the mechanism between TCM and intestinal bacteria, as well as the development trend were proposed, too.</span