Sandra Márcia Cesário Pereira da Silva

Assessment of domestic landfill leachate toxicity to the Asian clam Corbicula fluminea via biomarkers

In order to evaluate the effects of domestic landfill leachate to bivalves Corbicula fluminea, clams were exposed to different leachate concentrations (v/v): 2, 3, 6 and 10 percent, corresponding to dilutions observed along a stream that receives this effluent, or only to clean water for comparisons. After 5 and 15 days of exposure the activity of the biotransformation enzymes 7-ethoxyresorufin-O-deethylase (EROD) and glutathione S-transferase (GST), the multixenobiotic resistance mechanism (MXR) and lipid peroxidation (LPO) in gills and digestive gland and metallothionein (MT) content in gills were evaluated. Differences in biomarkers responses were observed between gills and digestive gland, except for MXR that decreased in both tissues of clams exposed to 6 percent for 5 days. EROD activity in gills was reduced in all leachate concentrations after 5 days and only in 2 percent after 15 days exposure, while an EROD increase was observed in digestive gland after 15 days exposure to 6 percent. GST activity increased only in the gills of clams exposed to 10 percent for 5 days. LPO varied between tissues and different conditions. A significant increase in LPO was observed in the gills, after 5 days exposure to 2 and 6 percent, and in digestive gland after 5 and 15 days exposure to 2 and 3 percent. MT content in the gills increased after 15 days exposure to 2 percent. In conclusion, different leachate concentrations tested here caused biochemical changes in C. fluminea, but due to the observed variability in biomarkers responses among leachate concentrations, it was difficult to determine patterns or thresholds concentrations.

Geophysical technique and groundwater monitoring to detect leachate contamination in the surrounding area of a landfill – Londrina (PR – Brazil)

The aim of the present study was to define leachate plume by using two techniques: geophysical and groundwater sampling in order to evaluate groundwater contamination. After performing a topographic survey and using geophysics, the leachate plume was identified. With this data, the wells for groundwater monitoring were located. Groundwater samples were analyzed for: COD, BOD, pH, alkalinity, conductivity, TKN and heavy metals. Through the electroresistivity method it was possible to define the shape of plume contamination. This method was important to locate the groundwater monitoring wells. The results of the physicochemical parameters showed the suitability of the geophysical study. The highest values of electric conductivity and alkalinity correspond to the wells located in the area interpreted as contaminated by leachate in the map of the resistivity. Even with seasonal variations, BOD values are low if compared to Brazilian environmental regulations, but COD values are higher up to 40 times the values of BOD. The concentrations of Ni, Zn, Cd and Cu in the groundwater are below the limits established by the potable water quality standards in Brazil, except for Pb whose concentration in groundwater were higher if compared to Brazilian legislation.

COD removal and toxicity decrease from tannery wastewater by zinc oxide-assisted photocatalysis: a case study

This work reports the optimization of degradation conditions and toxicity decrease in the tannery wastewater, collected in the retanning and dyeing steps. This effluent was filtered, diluted in a 1:200 proportion, and investigated as a case study on a bench scale by heterogeneous photocatalysis. These conditions were attained when the suspension, containing 1 g L−1 of ZnO and effluent, was irradiated for 4 h at pH 8.0 and 30°C. Physico-chemical parameters such as chemical oxygen demand (COD) decreased from 15,023 to 350 mg O2 L−1; fifth-day biochemical oxygen demand (BOD5) from 4374 to 10 mg O2 L−1; total solids from 28,500 to 188 mg L−1; total organic carbon (TOC) from 4685 to 4.93 mg L−1, and turbidity from 331 to 1.15 NTU after 4 h of irradiation. The LC50 increase from 14.90% to 56.82% in the lethality assay of Artemia salina L. microcrustacean as well as the dissolved oxygen of 6.45 mg L−1 indicated efficiency in this treatment.

Contaminação por chorume e sua detecção por resistividade

Resistivity geophysical techniques were applied closed to the Londrinas county sanitary landfill, allowing the detection and mapping of leachate contamination plume. The study area lies on the Parana Basin which is locally represented by basaltic rocks of the Serra Geral Formation. A correlation between lower resistivity values and the supposed leachate contaminations was stablished, once the electrical conduction, under natural conditions, occurs mainly in an ionic way, which are normally presented in the leachate. The main contamination flows in a general SE direction. An unexpected finding of this work was the detection of another flux direction of contamination plume to SW, which flows trough horizontal fractures or alteration surfaces of basaltic contacts.

Remoção de carga orgânica recalcitrante de lixiviado de resíduos sólidos urbanos pré-tratado biologicamente por coagulação química-floculação-sedimentação

The utilization of physical-chemical post treatment on landfill leachate has been an option employed to remove organic compounds from this effluent. In this way, this article aimed to evaluate the physical-chemical treatment by coagulation-flocculation-sedimentation as an alternative in the post-treatment of landfill leachate submitted to biological treatment. Consequently, it was used a Jar-test to monitor true color and chemical oxygen demand (COD) in order to evaluate the efficiency of the physical-chemical treatment. By means of factorial design and analyzing the results, it was found that the best removals of color and COD were attained by combining a dosage of 400 mg Fe+3/L with pH 3.0, achieving 98 and 81% of color removal and COD, respectively.

ADIÇÃO DE POLIELETRÓLITO AO PROCESSO DE FLOCULAÇÃO NO PÓS-TRATAMENTO DE LIXIVIADO POR COAGULAÇÃO-FLOCULAÇÃO-SEDIMENTAÇÃO

The addition of polyelectrolyte flocculation process in the physical-chemical treatment by coagulation-flocculation-sedimentation effluent has been an alternative to obtain clarification of good quality in less time due to increased sedimentation rate. Thus, this article aimed to determine the interrelationships between the pH gradient, flocculation, iron dosage and type of polyelectrolyte and evaluate the effect of this addition on color removal, COD and turbidity in the post-treatment of the leachate subjected to pretreatment biological. Through the use of technical planning and analyzing the results, it was found that the polymer cationic charge introduced himself as the most efficient, achieving removals of up to 97.70% for true color, 81.52% for COD and 92.18% for turbidity.