Characterization and chlorine reactivity of particulate matter released by bathers in indoor swimming pools.

Disinfecting swimming pool water is essential for preventing waterborne diseases. An unforeseen consequence of treating water with disinfectants is the formation of disinfection by-products (DPBs) that can cause harmful effects to health through the interactions between the added disinfectant and organic matter in the water. The present work focuses on the chlorine reactivity with particles released by bathers. Such particles are collected in the filter backwash water of swimming pools and this study intends to distinguish DPBs generated from dissolved chemicals from those formed by particulate matter. Therefore, filtered and unfiltered backwash waters were collected from several swimming pools, analysed physicochemically and chemically, and then chlorinated as is (79 mgL-1) and as diluted suspensions (36.2 and 11.9 mgL-1) at varying concentrations of chlorine (1.2 mg and 24 mgCl2L-1). Utilizing a DPD colorimetric technique and GC-ECD, respectively, the kinetics of chlorine consumption and DPBs production have been investigated. Up to 25.7 µgL-1 of chloroform was produced within 96 h at 1.2 mgCl2L-1, followed by haloacetic acids (HAAs) and haloacetonitriles (HANs). Within 96 h, the concentration of trichloroacetic acid reached a maximum of 231.8 µgL-1 at a chlorine concentration of 231.8 µgL-1. The formations of 0.13 µmol THMs, 0.31 µmol HAAs, and 0.04 µmol HANs per mg of dissolved organic carbon (DOC) were finally determined by correlating the organic content of particles with the nature of the DBPs generated. Comparing the quantities of DBPs generated in filtered and unfiltered samples helps us conclude that ∼50% of DBPs formed during the chlorination of swimming pool water are derived from particles brought by bathers.

Effects of humidity and glidants on the flowability of pharmaceutical excipients. An experimental energetical approach during granular compaction.

Granular materials are part of the design, production and final products of different industrial sectors. Powder flowability is a major topic in manufacturing and transport as it is closely related to process feasibility. Nonetheless, the flows of granular materials are not easy to describe or quantify, even in the simple case of dry monodisperse cohesionless particles. Flowability assessment is not a standard or normalized issue; still, no test is able predict powder flow behavior in all the different mechanical situations encountered during processing. This study aims (1) to evaluate flowability, as device-related, through the force or the energy supplied to the powder bed and (2) to study the effect of glidants and moisture content on flowability. To illustrate these aims, the flowability of two well-known pharmaceutical excipients, Avicel® PH-102 and Retalac® mixed with four different types of precipitated nano-silica (SIPERNAT® D10, D17, 50 S and 500 LS), was assessed using two granular compaction devices: Densitap® and FT4® compaction cell. Our results show that the hydrophilicity of colloidal silica affects surface coverage, ranging from 6% to over 80%. Binary mixtures with hydrophobic additives, D10 and D17, generated smaller silica aggregates with a wider spread on the surface of host particles. For Retalac® conditioned at 20% RH, HR values changed from 1.30 (acceptable flow) to 1.17 (good flow). For Avicel® PH-102, conditioned at 60% RH, HR values changed from 1.22 (fair flow) to less than 1.10 (excellent flow).

Integrated production of polyhydroxyalkanoates (PHAs) with municipal wastewater and sludge treatment at pilot scale.

A pilot-scale process was operated over 22 months at the Brussels North Wastewater Treatment Plant (WWTP) in order to evaluate polyhydroxyalkanoate (PHA) production integration with services of municipal wastewater and sludge management. Activated sludge was produced with PHA accumulation potential (PAP) by applying feast-famine selection while treating the readily biodegradable COD from influent wastewater (average removals of 70% COD, 60% CODsol, 24% nitrogen, and 46% phosphorus). The biomass PAP was evaluated to be in excess of 0.4gPHA/gVSS. Batch fermentation of full-scale WWTP sludge at selected temperatures (35, 42 and 55 °C) produced centrate (6-9.4 gCODVFA/L) of consistent VFA composition, with optimal fermentation performance at 42 °C. Centrate was used to accumulate PHA up to 0.39 gPHA/gVSS. The centrate nutrients are a challenge to the accumulation process but producing a biomass with 0.5 gPHA/gVSS is considered to be realistically achievable within the typically available carbon flows at municipal waste management facilities.

Polyhydroxyalkanoate (PHA) production from sludge and municipal wastewater treatment.

Polyhydroxyalkanoates (PHAs) are biodegradable polyesters with comparable properties to some petroleum-based polyolefins. PHA production can be achieved in open, mixed microbial cultures and thereby coupled to wastewater and solid residual treatment. In this context, waste organic matter is utilised as a carbon source in activated sludge biological treatment for biopolymer synthesis. Within the EU project Routes, the feasibility of PHA production has been evaluated in processes for sludge treatment and volatile fatty acid (VFA) production and municipal wastewater treatment. This PHA production process is being investigated in four units: (i) wastewater treatment with enrichment and production of a functional biomass sustaining PHA storage capacity, (ii) acidogenic fermentation of sludge for VFA production, (iii) PHA accumulation from VFA-rich streams, and (iv) PHA recovery and characterisation. Laboratory- and pilot-scale studies demonstrated the feasibility of municipal wastewater and solid waste treatment alongside production of PHA-rich biomass. The PHA storage capacity of biomass selected under feast-famine with municipal wastewater has been increased up to 34% (g PHA g VSS(-1)) in batch accumulations with acetate during 20 h. VFAs obtained from waste activated sludge fermentation were found to be a suitable feedstock for PHA production.

Photocatalytic conversion of gaseous nitrogen trichloride into available chlorine--experimental and modeling study.

In water, chlorine reacts with nitrogen-containing compounds to produce disinfection byproducts such as nitrogen trichloride which induces ocular and respiratory irritations in swimming pool workers. A technical solution has been used to reduce NCl3 exposure to acceptable levels, by adding a stripping step to the water recycling loop. The pollutants extracted are currently rejected into the atmosphere without treatment. However, the physical properties of NCl3 could be harnessed to induce its controlled degradation by direct or indirect light. This paper describes the way to transform NCl3 into oxidizing chlorine by photocatalysis under laboratory conditions. Photocatalytic oxidation efficiently degrades gaseous nitrogen trichloride, producing compounds such as HClO. About 60% of NCl3 decomposed was converted into HClO which could be used as a disinfection compound. A kinetic model is proposed for the photocatalytic process based on a convection/diffusion model. The Langmuir-Hinshelwood model was applied to the chemical part of the mechanism. The apparent quantum yield was also estimated to assess the optimal irradiance for NCl3 transformation. The results show that photocatalysis performs much better than photolysis alone for NCl3 removal, i.e. at least 25 times more efficient.

Minimisation of excess sludge production in a WWTP by coupling thermal hydrolysis and rapid anaerobic digestion.

In many cases, reducing sludge production could be the solution for wastewater treatment plants (WWTP) that here difficulty evacuating the residuals of wastewater treatment. The aim of this study was to test the possibility of minimising the excess sludge production by coupling a thermal hydrolysis stage and an anaerobic digestion with a very short HRT. The tests were carried out on a 2,500 p.e. pilot plant installed on a recycling loop between the clarifier and the actived sludge basin. The line equipped with the full scale pilot plant produced 38% TSS less than the control line during a 10 week period. Moreover, the rapid anaerobic digestion removed, on average, more than 50% of the total COD load with a hydraulic retention time (HRT) of 3 days. Lastly, the dryness of the remaining excess sludge, sanitised by the thermal hydrolysis, was more than 35% with an industrial centrifuge. This combination of thermal hydrolysis and rapid anaerobic digestion equally permits a significant gain of compactness compared to traditional anaerobic digesters.

Determination of short-term exposure with a direct reading photoionization detector.

The use of a direct reading photoionization detector (PID) to determine short-term solvent exposures is described in the present paper. To assess the relevance of such a total exposure evaluation it was necessary to compare it with the real concentration of pollutants. This comparison was made by measuring in parallel with the PID determination the concentration of each pollutant using a standard technique, i.e. sampling on charcoal tubes and subsequent analysis by gas chromatography. Laboratory tests showed that the linearity of the answer of the PID is good for many compounds and for a mixture of these compounds. Similar tests were carried out for painters in workplaces with the same good correlations (determination coefficient r2 close to 1) between the PID response and the real concentration of the pollutants measured on the sampling tubes. The use of PID also allowed determination of the exposure profile of the workers and comparison of the short-term exposure to the corresponding limit values. Many cases of the short-term limit values being exceeded were revealed by use of the PID, although very few cases of the long-term limit values have been found by the usual sampling (charcoal tube) and analytical (gas chromatography) methods.

Workplace monitoring of hydrogen peroxide using titanyl-coated sorbents.

The current methods of sampling hydrogen peroxide, based on bubbling in acid solutions (titanium tetrachloride or titanium oxysulfate), are unsuitable for personal sampling. An alternative medium has been developed: silica gel coated with titanium oxysulfate. Sample tubes of this new sampling medium are suitable for personal sampling. The sampling performance is the same as that of the methods based on bubbling, but the tubes must be desorbed as soon as possible, even if the spectrophotometric analysis can be postponed. Special emphasis has been placed on the possible interference by peracetic acid, which is currently used in conjunction with hydrogen peroxide in the food industry.