Yves Richard

Guideline for Measurement of Ozone Concentration in the Process Gas From an Ozone Generator

Abstract A joint meeting of members of the Quality Assurance Committees of the International Ozone Association Pan American Group (PAG), European-African Group (EAG), and Nippon Islands Group (NIG) was held in Oxford, Ohio on November 8 and 9, 1995. The purpose of the meeting was to establish a single, shared guideline for ozone concentration measurement in the gas phase and, in particular, from commercial ozone generators.

Removal of 2,4,6-trichlorophenol and natural organic matter from water supplies using PAC in floc-blanket reactors

Abstract The objective of this study was to evaluate the addition of powdered activated carbon (PAC) to upflow floc-blanket reactors for the adsorption of natural and synthetic organic chemicals. A 15.5-1. bench-scale floc-blanket reactor was operated with PAC addition for the adsorption of 2,4,6-trichlorophenol (TCP) and natural organic matter from one groundwater and two surface waters under laboratory and field conditions, respectively. Influent TCP concentrations ranged from 21 to 415 μg/l. The PAC doses ranged from 2 to 12 mg/l. While the hydraulic residence time in the floc-blanket reactor varied from 15 to 30 min, the carbon residence time ranged from 9 to 34 h. This is due to the high solids concentration in the floc blanket, which ranged from 1200 to 8700 mg/l. Comparison between the extent of TCP adsorption through the floc-blanket reactor and the equilibrium adsorption isotherms of TCP on PAC showed that the maximum adsorption capacity of PAC for TCP was utilized in the reactor. However, this study showed that the maximum adsorptive capacity of the carbon in a continuous process is dependent on the influent adsorbate concentration. This was in agreement with isotherm studies conducted with varying initial TCP concentration. The maximum PAC adsorption capacity for natural organic matter was also achieved in the floc-blanket reactor.

DENITRIFICATION OF WATER FOR HUMAN CONSUMPTION

ABSTRACT The nitrates contained in the waters destined for human consumption can be removed by a biological denitrification process using submerged, upward-flow type anaerobic filters. Depending on the waters rising velocity and the support materials characteristics, use is made of fixed or expanded beds. The treatments for nitrogen compound removal from wastewaters - nitrification, denitrification - are already known but still not widely applied. For certain potable water supply sources, nitrogenous pollution must now be removed using new processes well suited to potable water treatment. The authors study and model the specific properties of expanded beds. The results obtained in denitrification make it possible to calculate the maximum denitrification rate and the half-saturation coefficient with respect to phosphorus: Under normal running conditions, the amount of nitrates removed in an expanded bed reactor depends on the sludges concentration, the support materials concentration, the height, fluid velocity and temperature:

Ozone Water Demand Test

Abstract The paper describes the method, recommended by the Quality Assurance Committee of the European-African Group of the International Ozone Association, for the determination of the ozone demand of a water. For that laboratory test, ozone can be injected as a gas, or as a solution of ozone in water. The paper delineates the main analyses of the water which are needed to characterize the water, and as well as the framework of presentation of the results: table and graph.

Use Of Ozone And Flotation For The Treatment Of A Reservoir Water: The Dinan Case History

Abstract The plant of Dinan supplies water to the urban district of Dinan (Brittany-France). The raw water is a dam water, soft, containing iron and manganese, highly colored with a high content of organic carbon. The area providing water to the dam is rural country, so water also contains residues of agricultural practices such as pesticides and nitrates. During summer, algae blooms may occur. The old plant (including prechlorination, coagulation, flocculation, settling and sand filtration) has been replaced with a treatment line including: remineralization, preozonation, flotation, ozonation and granular activated carbon. Nitrate removal will be considered in the future. The paper presents the results obtained in the plant, the optimization of the preozonation dose as well as comparison with laboratory tests. A special reference concerns algae removal.

Importance of Ozone in Oxidation Processes for the Treatment of Potable Water Interference with other Oxidations

Injection points are determined not only on the basis of the direct action of ozone but also on its indirect effects such as its biological action within the sand or the granular activated carbon filters, and more especially on its interaction with other oxidants such as chlorine or chlorine dioxide which may be combined with ozone within a given treatment line.

Etude de l'inhibition de la nitrification par les composés organiques

Organic compounds likely to inhibit nitrification are numerous. The literature is rich in quantitative results but interpretation of these results is rarely attempted. Our study presents the inhibition constant determination of some phenolic and naphtholic products and proposes a theoretical approach of inhibition with emphasis on the structure. On a nitrifying mixed biomass, we have studied, in batch experiments, the effects of following organic pollutants on the nitrification: phenol; 2,4,5 trichlorophenol; 1-naphthol; 2 chloro-1-naphthol; 4 chloro-1-naphthol; 2,4 dichloro-1-naphthol. Our trials were conducted with mixed biomass (not only nitrifying bacteria) and, for the phenol, we observed inhibition that disappears when phenol is degraded. The phenol is highly toxic for nitrifying bacteria (Figs 1 and 2). For non biodegradable naphtholic components the model: 1i=r0r0−r=K1I+b allows the determination of KI (inhibition constant) (Fig. 3). In dynamic experiments on biological filters, the study of the support role in nitrifying fixed bacteria inhibition has been carried out by comparing two different organics in particular: methanol (very little adsorbable aliphatic compound) and phenol (aromatic compound very well adsorbed on activated carbon). The two supports compared were expanded clay and activated carbon. The results obtained show that an adsorbing support can retain adsorbable compounds, removing toxicity observed for non supported or fixed or non adsorbing material ones (Fig. 4). For the naphthol family, we have calculated electronic structures using the M.N.D.O. method. We obtained also energies of low unoccupied molecular orbitals (L.U.M.O.) and high occupied-molecular orbitals (H.O.M.O.) Relations between the energy of L.U.M.O., the energy difference between the two frontier orbitals, pKa and toxicity have been established. We show a correlation of Ki with pK and EBV and ΔE (Fig. 5, Table 4).

STUDY OF THE NITRIFICATION OF SURFACE WATER

Ammonia in surface waters which are to be used for producing potable water can be removed by filtration through a submerged biological filter using pozzolana as the filter medium. The ammonia concentration in successive layers of the filter is directly related to the vertical distribution of the biomass (ATP measurement) in the filter and to the filtration rate. The maximum quantity of ammonia removable by this type of filter is directly proportional to the retention time and to the temperature, according to the following relationship :

Preozonation Related to Algae Removal A Case History : The Plant of Mont-Valérien

Abstract The plant of Mont-Valerien supplies drinking water to the western suburbs of Paris. The plant has been upgraded, including a preozonation step. The plant has been operated with different doses of ozone applied during the preozonation step, and with different doses of coagulant for clarification. The purpose of that field test was to determine the best operating conditions to obtain the minimum of algae cells in the treated water. The results show that the minimum of algae cell count is obtained when the coagulant dose nullifies the zeta potential, and with an optimum dose of ozone.

Influence of Preozohation on Clarification by Flotation for Drinking Water Treatment

Abstract A preozonation study has been done at the potable water treatment plant of Moulle, in the North of France. The water is particularly rich in organic matter, with also algal blooms every, year, so the coagulan t treatmen t dose which is necessary for an optimal treatment, is very high. Previous laboratory tests have shown the importance of a preoxidation step, before the coagulation–flocculation–sedimentation industrial treatment line. It is also well known that flotation permits a significant reduction of coagulant dose. In addition, prechlorination of a water containing a large amount of organic matter induces the formation of a relatively high concentration of haloforms.