Biostability in distribution systems in one city in southern China: Characteristics, modeling and control strategy

This study investigated the bacterial regrowth in drinking water distribution systems receiving finished water from an advanced drinking water treatment plant in one city in southem China. Thirteen nodes in two water supply zones with different aged pipelines were selected to monitor water temperature, dissolved oxygen （DO）, chloramine residual, assimilable organic carbon （AOC）, and heterotrophic plate counts （HPC）. Regression and principal component analyses indicated that HPC had a strong correlation with chloramine residual. Based on Chick-Watson＇s Law and the Monod equation, biostability curves under different conditions were developed to achieve the goal of HPC 100 CFU/mL. The biostability curves could interpret the scenario under various AOC concentrations and predict the required chloramine residual concentration under the condition of high AOC level. The simulation was also carded out to predict the scenario with a stricter HPC goal （≤50 CFU/mL） and determine the required chloramine residual. The biological regrowth control strategy was assessed using biostability curve analysis. The results indicated that maintaining high chloramine residual concentration was the most practical way to achieve the goal of HPC ≤ 100 CFU/mL. Biostability curves could be a very useful tool for biostability control in distribution systems. This work could provide some new insights towards biostability control in real distribution systems.

Hydrogen-bonding regulated supramolecular chirality with controllable biostability

The regulation of natural helical nanostructures is principally supported and actuated by hydrogen bonds(H-bonds)formed from hydrogen-bonding groups(peptide bonds and base pairs)to realize biological activities and specific biofunctional transformations.However,studying the role of H-bonding patterns on the handedness of supramolecular assemblies is still challenging,since supramolecular assemblies will be disassembled or destabilized with slightly varying H-bonding groups for most supramolecules.To circumvent this issue,herein,two types of self-assembled C2-symmetric phenylalanine derivatives differed by a single H-bonding group(ester or amide)are systematically designed for deciphering the role of H-bonding pattern on the chirality of supramolecular assemblies and their related biostability.Opposite handedness nanofibrous structures with tailorable diameter and helical pitch are achieved with the transition from ester to amide groups in the gelators.Experimental and theoretical evidence suggests that helical orientation of ester-containing gelators ascribes to intermolecular H-bonds.In contrast,the helical direction for the amide-counterparts is mainly due to intra-and intermolecular H-bonds.Moreover,these H-bonding groups greatly influence their stability,as revealed by in vitro and in vivo degradation experiments and the left-handed assemblies are more stable than the right-handed ones.Thus,the study offers a feasible model to have valuable insight into understanding the role of H-bonding patterns in biological folding.

Experimental study using the dilution incubation method to assess water biostability

Water biostability is of particular concern to water supply as a major limiting factor for heterotrophic bacterial growth in water distribution systems. This study focused on bacterial growth dynamics in the series dilution of water samples with TOC（total organic carbon） values determined beforehand. The results showed that the specific growth rate of Pseudomonas fluorescens P17 varied dramatically and irregularly with TOC value when TOC concentrations were low enough during the initial periods of incubation under given conditions. According to this relationship between bacterial growth rate and TOC, a dilution incubation method was designed for the study of water biostability. With the method under a given condition, a turning-point TOC value was found at a relatively fixed point in the curve between bacterial growth rate and TOC of water sample, and the variation of growth rate had different characteristics below the turning-point TOC value relative to that over this value. A turning-point TOC value similarly existed in all experiments not only with tap water, but also with acetate and mixed solutions. And in the dilution incubation method study, the affections were analyzed by condition factors such as inoculum amount,incubation time and nature of the organic carbon source. In very low organic carbon water environments, the variation characteristics of bacterial growth rate will be useful to further understand the meaning of water biostability.

Pilot plant study on ozonation and biological activated carbon process for drinking water treatment

A study on advanced drinking water treatment was conducted in a pilot scale plant taking water from conventional treatment process. Ozonation-biological activated carbon process （O3-BAC） and granular activated carbon process （GAC） were evaluated based on the following parameters： CODMn, UV254, total organic carbon （TOC）, assimilable organic carbon （AOC） and biodegradable dissolved organic carbon （BDOC）. In this test, the average removal rates of CODMn, UV254 and TOC in O3-BAC were 18.2%, 9.0% and 10.2% higher on （AOC） than in GAC, respectively. Ozonation increased 19.3-57.6 μg Acetate-C/L in AOC-P17, 45.6-130.6 μg Acetate-C/L in AOC-NOX and 0.1-0.5 mg/L in BDOC with ozone doses of 2 8 mg/L. The optimum ozone dose for maximum AOC formation was 3 mgO3/L. BAC filtration was effective process to improve biostability.

Factors Affecting Bacterial Growth in Drinking Water Distribution System

Objective To define the influence of some parameters, including assimilable organic carbon (AOC), chloramine residual, etc. on the bacterial growth in drinking water distribution systems. Methods Three typical water treatment plants in a northern city (City T) of China and their corresponding distribution systems were investigated. Some parameters of the water samples, such as heterotrophic plate content (HPC), AOC, CODMn, TOC, and phosphate were measured. Results The AOC in most water samples were more than 100 μg/L, or even more than 200 μg/L in some cases. The HPC in distribution systems increased significantly with the decrease of residual chlorine. When the residual chlorine was less than 0.1 mg/L, the magnitude order of HPC was 104 CFU/mL; when it was 0.5-0.7 mg/L, the HPC was about 500 CFU/mL. Conclusion For controlling the biostability of drinking water, the controlling of AOC and residual chlorine should be considered simultaneously. The influence of phosphors on the AOC tests of water is not significant. Phosphors may not be the limiting nutrient in the water distribution systems.

Structural Comportment of Extract of Bougainvillea xbuttiana Flower Incorporated in Silica Xerogel Matrix

Measurement of the fluorescence comportment of Bougainvillea xbuttiana flowers embedded in silica xerogels matrix prepared with two different water to tetraethyl-orthosilicate [Si(OC2H5)4] ratio molar of 11 and 5, without heat-treatment, we report the grade of biostability of compound. The structural comportment for the PSI and PSII present in Bougainvillea flower is similar to the structural comportment for these photosystems present in leaves when they are incorporated on inorganic matrix such as silica xerogels. The contribution of the natural pigment of this kind of flower such as betalains which consist of betaxanthins and betacyanins, determines their colors contributed in the range of wavelength from about 550 nm to 660 nm.

Thermo-Stability of Natural Products Based on Chlorophyll Species Embedded in Silica Xerogel

This work studied the thermostability and the biostability of chlorophyll species obtained from an extract of spinach leaves embedded in a silica xerogel matrix. The analysis was done by monitoring the photosystem II (PSII) using fluorescence spectroscopy. Samples were prepared using the sol gel method with a molar ratio of ethanol/H2O/TEOS of 4:11.6:1. Then, silica xerogel matrix was loaded with an extract of spinach leaves, obtained in dark conditions. The measurement of the fluorescence spectra was done at selected temperatures to the corresponding non-physiological regimen. Results indicate that the PSII band position remains unchanged when heat treatment temperature increases up 200°C. For temperatures above 100?C, the fluorescence intensity diminishes linearly when the temperature increases. The photosystem II embedded in silica xerogel matrix is decomposed at temperatures above 200°C.

Stimuli-responsive gel-micelles with flexible modulation of drug release for maximized antitumor efficacy

Engineered stimuli-responsive drug delivery devices hold vast promise in biological applications for disease treatment due to their maximized therapeutic efficacy In this study a novel, stably cross-linked, and pH-sensitive biodegradable gel-micelle was constructed with amphiphilic conjugates of trimethylene dipiperidine- methacrylic anhydride-hyaluronic acid-stearylamine （TMDP-MA-HA-SA, TMHS） to improve tumor-targeting with flexible intracellular delivery of paditaxel （PTX）. The cross-linked methacrylate bonds significantly improved the biostability of TMHS gel-micelle （~ 200 nm） over the non-cross-linked under physiological conditions, while hyaluronic acid plays an important role in active tumor targetability. The gradual degradation of cross-linked hyaluronic acid shell was triggered by the concentrated hyaluronidase. Meanwhile, under acidic conditions （pH 〈 6.5）, the tertiary amines of pH-sensitive TMDP moieties were protonated and thereby solubilized the gel-micellar core-portions. The resultant pH-triggered inner-core spaces rapidly prompted PTX release in the presence of multiple cytosolic enzymes that mainly degraded the remaining hydrophobic stearylamine core. During the in vitro cytotoxicity assay, PTX-loaded TMHS gel-micelles （ct~） revealed anticancer efficacy against human hepatocellular carcinoma HepG2 cells with ICs0 of 1.42 gg/mL （PTX concentration）, significantly lower than other groups. In parallel, the in vivo anti-tumor efficacy of CLTMHSptx gel-micelles against BALB/c xenograft tumor animal model demonstrated the greater tumor growth inhibition capacity of 72.06%, compared to other treatment groups at a safe concentration. Consequently, the cross-linked and stimuli-responsive CLTMHSFrx gel-micelles hold a great potential for flexible modulation of intracellular delivery of hydrophobic anticancer drugs with maximized antitumor efficacy.