On-site Mass Research Articles

Experimental and Numerical Simulations Predictions Comparison of Power and Efficiency in Hydraulic Turbine

On‐site power and mass flow rate measurements were conducted in a hydroelectric power plant (Mexico). Mass flow rate was obtained using Gibson′s water hammer‐based method. A numerical counterpart was carried out by using the commercial CFD software, and flow simulations were performed to principal components of a hydraulic turbine: runner and draft tube. Inlet boundary conditions for the runner were obtained from a previous simulation conducted in the spiral case. The computed results at the runner′s outlet were used to conduct the subsequent draft tube simulation. The numerical results from the runner′s flow simulation provided data to compute the torque and the turbine′s power. Power‐versus‐efficiency curves were built, and very good agreement was found between experimental and numerical data.

Limiting the emissions of micro-pollutants: what efficiency can we expect from wastewater treatment plants?

The next challenge of wastewater treatment is to reliably remove micro-pollutants at the microgram per litre range in order to meet the environmental quality standards set by new regulations like the Water Framework Directive. The present work assessed the efficiency of different types of primary, secondary and tertiary processes for the removal of more than 100 priority substances and other relevant emerging pollutants through on-site mass balances over 19 municipal wastewater treatment lines. Secondary biological processes proved to be in average 30% more efficient than primary settling processes. The activated sludge (AS) process led to a significant reduction of pollution loads (more than 50% removal for 70% of the substances detected). Biofilm processes led to equivalent removal efficiencies compared to AS, except for some pharmaceuticals. The membrane bioreactor (MBR) process allowed to upgrade removal efficiencies of some substances only partially degraded during conventional AS processes. Preliminary tertiary processes like tertiary settling and sand filtration could achieve significant removal for adsorbable substances. Advanced tertiary processes, like ozonation, activated carbon and reverse osmosis were all very efficient (close to 100%) to complete the removal of polar pesticides and pharmaceuticals; less polar substances being better retained by reverse osmosis.

On-site evaluation of the efficiency of conventional and advanced secondary processes for the removal of 60 organic micropollutants

The next challenge of wastewater treatment is to reliably remove micropollutants at the microgram per litre range in order to reduce the discharge for priority substances and to meet the environmental quality standards set by the European Water Framework Directive. The present work assessed the occurrence of 60 organic substances (priority substances and other relevant pollutants) in municipal wastewater and sludge. Their fate in the treatment processes and their removal efficiencies were quantified. Thorough on-site mass balances were carried out at 8 municipal wastewater treatment plants chosen among conventional and advanced secondary processes. It was found that 70% of the substances were quantified in raw wastewater and 50% in effluent, with a transfer without a limited degradation for most of them. Low loaded activated sludge (AS) process reduced the emission of more than half of micropollutants. At low sludge retention time (AS under high load), lower removal efficiencies were measured compared to low loaded AS. No influence of temperature of the biological reactor was shown. The membrane bioreactor process increased the removal efficiencies for one third of the substances that were partially removed with AS. Still, five substances were measured at concentrations exceeding the environmental quality standards at the outlet of the studied plants. In addition to efforts for source-reduction, complementary treatments need to be set-up.

Intraspecific variation of Melaleuca quinquenervia leaf oils in its naturalized range in Florida, the Caribbean, and Hawaii

The invasive tree Melaleuca quinquenervia threatens the biodiversity of the Florida Everglades and adjacent areas. Biological control efforts have resulted in the release of three Australian insect species. Not all populations of the plant, however, are equally nutritious to the biological control agents. For example, previous results indicated that Oxyops vitiosa had reduced biomass and fecundity when fed different M. quinquenervia chemical variants. To find suitable sites for release of this herbivore species and locations where nursery sites can be developed for mass production of weevils, we studied the natural terpenoid variation in this plant throughout its range in Florida. For comparison, we also examined the terpenoid variation in naturalized populations in the Caribbean, Hawaii, and Australia. We found that two chemical variants or chemotypes exist in Florida, each dominated by one sesquiterpene, either E-nerolidol or viridiflorol. In the 28 populations studied in Florida no regional trends in chemotype dominance were found. More than half (16 of 28) of the populations were composed of between 34 and 66% of both chemotypes. A similar number of populations were dominated (>66%) by either the E-nerolidol (eight populations) or the viridiflorol (six populations) chemotype plants. Additionally, the total amount of terpenoids in leaves from plants grown north of the invasive range of M. quinquenervia was significantly reduced compared with invasive populations. The total amount of terpenoids in leaves from plants grown in Australia and the Caribbean was significantly greater than those in leaves from Florida and Hawaii. These results identified eight populations that would be most suitable for initial releases and where field nurseries could be established for on-site mass production.

Fast and direct screening of polyaromatic hydrocarbon (PAH)‐contaminated sand using a miniaturized membrane inlet mass spectrometer (mini‐MIMS)

A miniaturized membrane inlet mass spectrometer (mini-MIMS; total weight 10 kg everything included) was equipped with a small sample cell using a flat sheet silicone membrane mounted close to the ionizing region of a multipole mass spectrometer. Spiked sand samples were placed in small stainless steel vials and dropped into the heated sample cell (>150 degrees C). A hole in the vial in front of the membrane and above the sand made it possible for the polyaromatic hydrocarbon (PAH) residuals to penetrate the membrane and enter the mass spectrometer as they evaporated from the sample. Using this simple setup we were able to quantitatively (approximately 10% relative standard deviation (RSD)) detect PAHs with up to five aromatic rings and with detection limits in the low parts-per-million (ppm) range. The vial system solves one of the major difficulties in analysis of larger PAHs using a MIMS. Normally, analysis of PAHs with more than two rings is hampered by a long memory effect due to the sticking of the PAHs to the inlet system, the membrane and surfaces in the vacuum system. By removing the vial from the sample cell within 2 min, we were able to analyze samples at 5-10 min intervals. The preliminary laboratory experiments presented here show much promise with respect to the development of a hand held (<10 kg) on-site mass spectrometry system for PAH screening at contaminated sites.

On-Line Mass and Energy Balance of Paper-Machine Dryers in the Purpose of Saving Energy

A mini-computer installed in a caravan has recently been started by the technical assistance team of the French Pulp and Paper Research Institute with the purpose of making on-site mass and energy balances around paper machine dryers. The methods used for elaborating wet air, steam and condensates parameters are first described. The main features of the designed software (adaptability to different machine structures) are then presented applied to the case of an average industrial paper machine. The short delay before getting elaborated process data and balance computations largely enhance the possibilites of on-site trouble-shooting of the team.

A New Technique for the Rapid Analysis of Soil for the Presence of Polychlorinated Biphenyls

Abstract A new technique for rapidly screening for the presence of PCBs in soil has been developed and tested in a field monitoring situation. The technique employs an atmospheric pressure chemical ionization mass spectrometer system mounted in a van to provide on-site mass spectrometric identification and quantitation of the compounds. A small soil sample is heated in a flowing stream of pure nitrogen, and the vaporized material is trapped on an adsorber which is thermally desorbed into the ion source of the mass spectrometer. A detection limit of approximately 1 /ig/g of Aroclor 1254 has been achieved, with a total analysis time per sample of approximately 5 minutes. The process makes possible the direct analysis of soil samples without any chemical workup or preseparation.