Sérgio João De Luca

Sodium Ferrate (IV) and Sodium Hypochlorite in Disinfection of Biologically Treated Effluents. Ammonium Nitrogen Protection against THMs and HAAs

The work described in this paper presents an evaluation of disinfection by-products generation in four different biological treatment plant effluents, making use of sodium hypochlorite and sodium ferrate (IV) at varying concentration and reaction time. Correlations between pH, chemical oxygen demand, total organic carbon, ammonium nitrogen, combined chlorine and trihalomethanes (THMs) and haloacetic acids (HAAs) were carried out. Disinfection by-products generation presented a direct relation with concentration and sodium hypochlorite reaction time. For the highest hypochlorite concentration employed (20 mg L−1) and highest reaction time (168 h), the THMs total did not exceed 312.96 μg L−1, a value that lies below the Brazilian emission standard for treated effluents (1 mg L−1 of chloroform). The THMs presented an inverse correlation with ammonium nitrogen, when inverse (R2 = 0.646; P < 0.001) and exponential (R2 = 0.707; P < 0.001) function were used. As per HAAs this same relation was observed for logarithmic (R2 = 0.0397 P < 0.001) and exponential (R2 = 0.508; P < 0.001) functions. The more nitrified the effluent, the bigger the chlorinated disinfection by-product generation. The disinfectant sodium ferrate (IV) does not lead to halogenated by-product formation.

Índice de impacto dos resíduos sólidos urbanos na saúde pública (IIRSP): metodologia e aplicação

The reduction in the number of diseases produced directly or indirectly by municipal solid waste depends on an efficient collection and appropriate final disposal. With the information obtained from a questionnaire sent to the Rio Grande do Sul municipalities, divided into seven homogeneous regions, indicators were developed and, by means of non-parametric statistical procedures, eight index were structured (specific indices), which form a general quality control index for solid wastes services. In this paper is presented a summary and an example of the methodology used to create the Impact Index of Solid Waste Management Systems on Public Health (IIRSP), which more directly reflects the solid waste-man-public health relationship.

Técnicas de cultivo de arroz irrigado: relação com a qualidade de água, protozoários e diversidade fitoplanctônica

The purpose of this study was to evaluate the effect of techniques of rice cultivation on the physical, chemical and biological parameters of effluent water. The research was conducted at the Experimental Station of IRGA (Rio Grande do Sul Rice Institute), in the municipality of Cachoeirinha, RS, in the Gravatai river basin. The tests were performed using 3 usual techniques of rice cultivation, conventional, pre-germinated and direct planting. During the first 30 days of irrigation, the physical and chemical parameters of the paddy fields presented higher values compared to that of inflow. This shows that during this period the impact on water quality was highest. After this period, the situation changed completely. After reaching adult size, the rice plants acted as a natural swamp, extracting most of the contaminants from the water and the soil until the harvest. Thus the impact of rice farming is more concentrated during the first 30 days of irrigation was confirmed and it can be concluded that, depending on the cultivation technique used, there is efficient decontamination of the irrigation water. The most efficient technique was the direct planting.

Síntese eletroquímica do ion ferrato(VI)

The optimization of ferrate(VI) ion generation has been studied due to its favorable characteristics for application in several fields, including environmental quality control. The paper presents the best conditions for electrolytic generation of ferrate(VI) in alkaline media. An appropriate electrolyte was NaOH, 10 mol/L. Circulation of the electrolyte solution was important to avoid acidification close to the anode surface. An anode pre-cleaning with 10% HCl was more efficient than a cathodic pre-polarization. Among the distinct anode materials tested, pig iron showed the best performance, allowing up to 20 g/L of Na2FeO4, in 10 mol/L NaOH solution to be obtained, after 7 h of reactor operation, which is a concentration higher than those found in literature for alternative processes.

Oxidação de microcistinas-LR em águas pelo íon ferrato(VI)

Algae toxins are becoming a severe problem in the water treatment industry, especially for human and animal consumption. Traditional treatment processes have failed in complying with water supply standards. Potassium ferrate(VI) is a powerful oxidant, disinfectant and, also, a coagulant. In this paper, the results of microcystin-LR oxidation by ferrate(VI) ion are presented. Kinetic and jar tests showed a average value of 0,012 min-1 for the pseudo first order reaction rate constant, for 100 and 200 µg.L-1 concentration of MC-LR. Ferrate(VI) dosages between 1.6 and 5.0 mg.L-1 suggest that water supply standards for MC-LR can be reached, which means that the oxidant may be employed as coadjuvant in water treatment.