RESUMEN
The present study was carried out to evaluate the cytotoxic effects of refinery wastewater collected from different stations of the Kizilirmak river on Vicia faba L. root tip cells. For this aim, we used the germination percentage, root length, weight gain and micronucleus (MN) frequency as indicators of cytotoxicity. Additionally to the cytological analysis, DNA analyses were performed in root tips meristems of Vicia faba seeds treated with refinery wastewater. Heavy metal concentrations in the water samples were determined using atomic absorption spectrophotometer (AAS). The concentrations of heavy metals in the water were in the order of Pb>Zn>Fe>Cu>Ni>Cd>Hg. The highest germination percantage was observed in the control group (in proportion as 96%). Heavy metals in the water samples collected from Station I, II and III caused a decrease in the germination percentage as 48, 18 and 30%, respectively. The highest root length and weight gain was observed in the control group at the end of the experimental period. The least root length and weight gain was observed in seeds treated with wastewater collected from Station I. In the control group, the weights of all the seeds increased about 4.08 g when compared with initial weight. The root lengths of the control seeds were determined as 6.38 cm at the end of the experimental period. The weights of the seeds exposed to wastewaters obtained from Station I, II and III increased about 1.08, 3.03 and 2.01 g according to initial weight, respectively. Microscopic examination of V. faba root tip meristem cells showed that any example of the MN formation was not seen in the control group. The highest frequency of MN was observed in group treated with wastewater collected from Station I and least frequency of MN was observed in group treated with wastewater collected from Station II. It was also observed that the yields of DNA in the seeds exposed to wastewater were lower than recorded in the controls. Hence, DNA yields exposed to wastewater were run ahead on agarose gel according to the control group. The results clearly indicate that refinery wastewater had important cytotoxic effects on V. faba root tip cells. It was also observed that V. faba seeds are very sensitive and useful biomarkers for monitoring these effects in waters contaminated with heavy metals.
RESUMEN
Neste trabalho, avaliou-se o efeito do tempo de detenção hidráulica (TDH) no desempenho de três reatores aeróbios inoculados com Aspergillus niger AN400, usados para tratamento de efluentes de refinarias de petróleo. Cada reator foi operado com um tempo de detenção hidráulica diferente: 4, 8 e 12 horas, durante 152 dias. Eles possuíam leito fixo de espuma de poliuretano e o escoamento era ascendente e contínuo. Determinaram-se: pH, fenóis, demanda química de oxigênio (DQO), amônia, nitrito e nitrato, no afluente e efluentes dos reatores. O TDH de oito horas foi o melhor para remoção de DQOsolúvel e não houve diferença entre os TDHs para remoção de fenóis totais. No período estável não houve remoção de nitrato; no entanto ocorreu remoção de nitrito de aproximadamente 99 por cento. Além disto, houve produção de amônia devido à amonificação a partir do nitrito presente no meio.
This paper evaluated the effect of hydraulic retention time (HRT) on the performance of three upflow aerobic reactors, with polyurethane foam as support material, inoculated with Aspergillus niger AN400, used for the treatment of petroleum refinery wastewater. Each reactor was operated with a different HRT: 4, 8 and 12 hours, during 152 days. The performance was evaluated based on pH; phenols; COD, nitrate and nitrite. The results show that for the COD removal, it is more reasonable to operate the reactor with HRT of eight hours. However, there was no difference among results of phenol removal efficiency of the different HRTs. During steady state condition, nitrite was removed in approximately 99 percent, but there was no reduction on the nitrate concentration. Ammonia was produced in all reactors, probably due to ammonification of nitrite.