Improvement of industrial wastewater treatment by aerated lagoon: case studies

This paper deals with the aerobic biological treatment of industrial wastewaters by aerated lagoons, when high flowrates are involved. A methodology is developed which gives the best fit between the biologic al reactions and the ideal hydrodynamic behaviour of the lagoon. This analysis, based on the real kinetics of the degradation process, leads to the minimum volume and the ideal behaviour of the lagoon needed to reach the degree of conversion required to respect the discharge regulations. Because the flow field of a lagoon is of "shallow waters" type, appropriate technologies have been designed in order to achieve the mixing (by fluidic deviator) and the aeration (by hydroejector) in such a lagoon. Some applications of these methodologies and technologies to industrial problems in the chemical industry (pulp and paper) and food industry (sugar) are presented. This original approach is suitable for modifying existing aerated lagoons, or for upgrading natural lagoons to aerated lagoons, to successfully meet the new legislat on on effluent quality.