Optimisation de la qualite de l'eau d'un bassin zoologique selon une approche multiparametre.

摘要

In a context where society is becoming aware of its impact on the environment, measures are taken to reduce the ecological footprint at both the individual and societal level. Nowadays, water is a resource that has an increasing economical and moral value. For this reason, it becomes increasingly important for businesses to reduce their water consumption. In the case of a company exploiting a semi-closed circuit zoological basin, this boils down to minimizing water consumption while meeting the predefined physico-chemical and biological quality criterias.;This approach relies on the fact that it is difficult when labor is not available to control all parameters that can alterate the physico-chemical and biological equilibrium in semi-closed water treatment circuit. The empirical treatment coefficients thus obtained for a given scenario lead to an integrated systemic overview with minimized sampling and analyzing time.;In the studied case of a zoological basin inside witch evolve an hippopotamus (Hippopotamus amphibius), the quality parameters studied were the ammonia concentration (NH3), the total organic carbon concentration (TOC), the fecal coliform concentration (FC), the residual ozone concentration (O3), turbidity, color, the ortho-phosphate concentration (PO43-) and the nitrite/nitrate concentration (NO 2-/NO3-). The model developed suggest that it is impossible with the current system (sand filtration, ozonation and activated carbon adsorption) to achieve the quality criterias with respect to turbidity (0.20 NTU) and fecal coliform concentration (200 CFU).;This study suggests that the sand filtration water flow is critical to achieving the turbidity related goal of treatment. A 47% upsizing of the sand filtration unit would achieve this goal in less than an hour after a turbid event. Also, in the event that alternative treatment options are considered, the goal could be attained with the implantation of a high flow pretreatment (212% the nominal flow of sand filtration) with 80% average turbidity removal efficiency. The reaching of the treatment objective related to the fecal coliform concentration involves the implantation of a very high flow pretreatment (3 times the nominal flow of sand filtration) combined with a 90% removal capacity.;The development of a simple treatment model including all processing units can provide information in sufficient quantity and quality to establish optimizing pathways for the water treatment system. The proposed approach is to treat all contaminants in a water treatment system of a zoological basin as a stream of material from which it is possible to approximate the amount remaining after each processing unit by a first order equation.;In this perspective, it might be interesting to evaluate technologies such as dissolved air flotation (DAF), preozonation or microfiltration; technologies which can handle high flow rates at low cost and low water consumption. With an insight of minimizing system water consumption, all these solutions should be subsequently evaluated by test pilots and appropriate economic studies where all the stakeholders are involved.;Paradoxically, the dilution of the zoological bassin water with the city tap water, which has a similar turbidity value, does not contribute to the achievement of treatment goals and enhance the water consumption level. Hence, a direct reduction in the daily turnover rate of water should be advocated.;Although highly dependent on the scenario studied, the approach used provided good avenues for optimization in a context where resources and expertise are limited. Its application also seeks to foster exchanges among experts, operators and managers; a key parameter in obtaining viable, profitable and environmentally responsible water treatment solutions in the management of a zoological basin.;Keywords: Zoological basin, water quality, information management, water treatment technologies.