Effects Of Ozone On The Production Of Biodegradable Dissolved Organic Carbon (BDOC) During Water Treatment

This article deals with the oxidation effect of ozone on the increasing fraction of biodegradable organic matter with the “ozotest” method, a laboratory technique which simulates the effect of ozonation and allows a complete oxidation assessment. Ozone treatment was performed on river water samples and sand filter effluent samples. Ozone consumption, reduction of UV absorbance and BDOC formation were monitored with applied ozone doses from 0 to 10 mg/L and with contact times from 0 to 60 min. The BDOC formation was optimum at an applied ozone dose of 0.25-0.5 mg O₃ per mg DOC (contact time = 5 min) corresponding to apparition of traces of residual ozone and maximum UV reduction. Maximum ozone consumption, UV reduction and BDOC formation occurred simultaneously during the first two minutes of treatment. Concerning BDOC formation, applied ozone dose showed a greater effectiveness than contact time. For the same quantity of consumed ozone, a short contact time associated with a high ozone dose was preferable to a long contact time and a low ozone dose.     

Well-balanced orientations of mixed graphs

We show that deciding if a mixed graph has a well-balanced orientation is NP-complete.     

Performance of Object Classification Using Zernike Moment

Moments have been used in all sorts of object classification systems based on image. There are lots of moments studied by many researchers in the area of object classification and one of the most preference moments is the Zernike moment. In this paper, the performance of object classification using the Zernike moment has been explored. The classifier based on neural networks has been used in this study. The results indicate the best performance in identifying the aggregate is at 91.4% with a ten orders of the Zernike moment. This encouraging result has shown that the Zernike moment is a suitable moment to be used as a feature of object classification systems.     

The Stackelberg Minimum Spanning Tree Game

We consider a one-round two-player network pricing game, the Stackelberg Minimum Spanning Tree game or StackMST. The game is played on a graph (representing a network), whose edges are colored either red or blue, and where the red edges have a given fixed cost (representing the competitor??s prices). The first player chooses an assignment of prices to the blue edges, and the second player then buys the cheapest possible minimum spanning tree, using any combination of red and blue edges. The goal of the first player is to maximize the total price of purchased blue edges. This game is the minimum spanning tree analog of the well-studied Stackelberg shortest-path game. We analyze the complexity and approximability of the first player??s best strategy in StackMST. In particular, we prove that the problem is APX-hard even if there are only two different red costs, and give an approximation algorithm whose approximation ratio is at most min?{k,1+ln?b,1+ln?W}, where k is the number of distinct red costs, b is the number of blue edges, and W is the maximum ratio between red costs. We also give a natural integer linear programming formulation of the problem, and show that the integrality gap of the fractional relaxation asymptotically matches the approximation guarantee of our algorithm.     

Performance of Object Classification Using Zernike Moment

Moments have been used in all sorts of object classification systems based on image. There are lots of moments studied by many researchers in the area of object classification and one of the most preference moments is the Zernike moment. In this paper, the performance of object classification using the Zernike moment has been explored. The classifier based on neural networks has been used in this study. The results indicate the best performance in identifying the aggregate is at 91.4% with a ten orders of the Zernike moment. This encouraging result has shown that the Zernike moment is a suitable moment to be used as a feature of object classification systems.     

Identification and characterization of bacterial activities involved in wastewater treatment by aerobic fixed-bed reactor

Bacterial colonization of an aerobic fixed bed reactor was studied as a function of reactor height and time during three days. After the colonization, the evolution of the quantity of fixed biomass, their hydrolytical activities and the influence of periodic backwashing were measured, weekly. Approximatively 100 bacteria were identified and classified in different metabolic groups. A decreasing gradient of biomass from top to bottom of the reactor was observed. Backwashing operation permitted the removal of 48% of the fixed biomass. In terms of bacterial strains and their potential hydrolytical abilities (glucidolytical, proteolytical, and lipolytical), no zonation was observed. Most of the species isolated from the granular support belong to the following genera and family: Acinetobacter, Enterobacteriaceae, Aeromonas, Flavobacterium, and Pseudomonas.     

Wastewater Disinfection : Elimination of Fecal Bacteria and Eneric Viruses By Ozone

Wastewater containing indigenous bacteria and enteric viruses was ozonated in a contact column with counter-current circulation of ozonated air and water. The mean slope of the inactivation curve for indigenous viruses is about half that observed for E. coli and fecal streptococci. For 3 rag osub3;/l, in the presence of residual ozone and a contact time of 19 min, inactivation of 1 log for the viral population and 2 logs for the fecal bacteria are observed. A negative correlation exists between inactivation and organic content.     

Effects Of Ozone-Hydrogen Peroxide Combination On The Formation Of Biodegradable Dissolved Organic Carbon

The effects of ozone and ozone/hydrogen peroxide on BDOC formation were studied with the “Ozotest” method, a laboratory technique that permits the assessment of oxidation efficiency. Oxidation treatments were performed on river water and sand filter effluent samples. Ozone consumption, reduction of UV absorbance, and BDOC formation were monitored during the experiments. The ratio of 0.35-0.45 mg H₂O₂ per mg O₃ used to degrade pesticides also was optimal for the oxidation of organic matter. BDOC formation versus ozone dose curves with ozone alone or ozone/peroxide system were similar. BDOC formation was optimum at an applied ozone dose of 0.5-1 mg O₃/mg C (contact time = 10 min). The ozone/peroxide system yielded lower BDOC values than ozone alone, a phenomenon related to differences in byproducts generated by the two oxidative systems. Moreover, reduction of the concentration of DOC was higher with ozone/hydrogen peroxide than with ozone alone. For both oxidant systems, BDOC formation occurred during the first minute of treatment.     

Coliforms and other microbial indicators occurrence in water and biofilm in full-scale distribution systems.

Biofilm and microbial water quality were studied in four middle size full-scale distribution systems (DS) in France serving 5,000-30,000 inhabitants (maximum residence time 23-160h) through three sampling campaigns over 1 year. Three of these DSs were chosen because of a quite high occurrence of bacterial indicators (i.e. total coliforms), the last DS was considered as a reference. Biofilm was studied on cast iron coupons incubated for more than 1 month in devices continuously fed with water from the DS in conditions imitating those met in DS. The devices were located at different points (4-6) along each DS. The abundance of bacteria in biofilm was estimated by heterotrophic plate counts (HPC) after detachment of the biofilm from the support by sonication. Microbiological water quality was estimated in parallel; analysis of total coliforms, E. coli, enterococci and anaerobic sulphide-reducing bacteria spores (ASRB spores) was carried out in biofilm and water. Over the period of the study, 171 water samples and 57 biofilm samples were collected. Over these 171 waters, 19 (11%) were positive for at least one of the measured indicators while two biofilm samples were positive (3.5%). Significant differences were observed in the levels of contamination between the DSs. High residence time in the DS, low disinfectant residual and high temperature increased the risk of indicator occurrence in the water phase. Due to the low number of biofilm samples positive for bacterial indicators, the data collected in the present study did not allow observation of a direct association between biofilm and water contaminations, even if the occurrence of indicators in water appeared on DSs with the highest density of biofilm (HPC).