Avaliação da acurácia de diversos métodos para determinação de ácidos graxos voláteis e alcalinidade a bicarbonato para monitoramento de reatores anaeróbios / Evaluation of the accuracy of several methods for determination of volatile fatty acids and bicarbonate alkalinity for the monitoring of anaerobic reactors

Sistemas de tratamento anaeróbios são sensíveis às mudanças de condições ambientais que influenciam no metabolismo dos microrganismos responsáveis pela estabilidade do processo. Os objetivos deste trabalho foram (i) avaliar a acurácia de métodos que determinam os parâmetros de controle ácidos graxos voláteis (AGV) e alcalinidade a bicarbonato (AB) em amostras preparadas com concentrações de 50 a 1000 mg/L e, (ii) verificar diferentes procedimentos de remoção de CO2 formado durante titulação ácida das amostras. A partir do teste estatístico de Tukey aplicado aos resultados obtidos, observou-se que os métodos Kapp e DiLallo & Albertson com utilização de ultra-som para a remoção de CO2 do meio líquido apresentaram os melhores resultados para AGV. Os métodos da Condutividade, Kapp e Jenkins se destacaram na determinação de AB.

Anaerobic treatment systems are sensitive to the environmental condition changes. Such changes may have influence on the metabolism of the microorganisms responsible for the process stability. The aims of this work were (i) to evaluate the accuracy of methods to determine control parameters volatile fatty acids (VFA) and bicarbonate alkalinity (BA) in samples prepared with concentrations from 50 to 1000 mg/L and, (ii) to verify different procedures of the CO2 removal formed during the acid titration of the samples. From the Tukey statistical test applied to the obtained results it was observed that the Kapp and DiLallo & Albertson methods using sonic equipment to remove CO2 from the liquid presented better results for VFA. The Conductivity, Kapp and Jenkins methods were considered the most reliable for BA determination.

Estimate of denitrifying microbiota in tertiary sewage treatment and kinetics of the denitrification process using different sources of carbon

A study of the kinetics of denitrification was carried out in the laboratory based on the quantification of N2O, the final product of the activity of denitrifying microorganisms, when the enzymatic reduction of N2O to N2 was blocked by acetylene. Concentrated mixed liquor (sludge from a reactor with intermittent aeration used for sewage treatment) was used as the inoculum, while methanol, acetic acid, glucose, effluent sewage from an anaerobic fluidized bed reactor and synthetic substrate simulating domestic sewage were used as carbon sources. The mean concentration of nitrate was 20 mg/L. Maxima of N2O production and NO3- consumption occurred between 0.5h and 2.0h of incubation using all the carbon sources, which characterized the denitrification process. Acetic acid and methanol were responsible for the highest rates of N2O production. The estimated number of denitrifying microorganisms in the reactor with intermittent aeration, using the MPN technique, varied from 10(9) to 10(10) MPN/g VSS, indicating a high potential for the occurrence of denitrification.