Clogging in constructed wetlands: Indirect estimation of medium porosity by analysis of ground-penetrating radar images.

Identification of the degree of porous medium clogging in constructed wetlands (CWs) is a complex procedure because bed obstruction is a phenomenon that occurs in the subsurface and involves several factors. Ideal methods must allow for subsurface analysis and be non-invasive, what is the case of ground penetrating radar (GPR or georadar) used for soil characterization. Thus, this work aimed to evaluate the use of GPR for clogging characterization of two full-scale horizontal subsurface flow constructed wetlands (HSSF-CWs), one unit planted with cattail (Typha latifolia) and the other unit with no vegetation. Both units received municipal sewage (50 p.e. each) previously treated in an anaerobic reactor, had been in operation for seven years (at the time the GPR was used) and showed signs of heavy clogging, leading to surface flow. In order to produce a standard for GPR image (created by the response of the reflected wave in the passage through different media) identification and association of colors with the environmental conditions inside the medium (cleaner or more obstructed condition), a clean granular rock filter (in operation for only one month), similar to the unplanted unit, was used. Equations developed for indirectly estimating the porosity, based on the RGB (red, green and blue) color scale, indicated that the methodology was in agreement with the visual conditions of surface flow occurrence in the HSSF-CW, showing to be a suitable non-invasive method to characterize the advancement of clogging in CWs.

Irrigation of eucalyptus plantation using treated bleached kraft pulp mill effluent.

The use of treated pulp mill effluent on eucalyptus plantation appears to be an attractive option for plant nutrition and water supply. It also constitutes a supplementary treatment process and a final disposal option for the mill effluent. This study aimed at the investigation and evaluation of the effects of bleached kraft pulp mill treated effluent on three typical Brazilian soils used for eucalyptus plantation. The effluent was characterized and five different application rates, defined according to the load of sodium, were tested in controlled environment experiments (greenhouse). After effluent application over a six month period an increase in the salinity of the studied soils was observed, although no soil dispersion was detected. The low content of some nutrients in the treated effluent indicated the need for fertilizer complementation. In general, the best biomass productivity and plant growth results were obtained in fine textured soil at a loading rate of 6.49 t Na ha(-1). The good response of the soil-plant system under different effluent application rates showed the feasibility for the eucalyptus irrigation if adequate management practices and monitoring are carried out.

Environmental assessment of water-courses of the Turvo Limpo River basin at the Minas Gerais State, Brazil.

A study was performed to evaluate the environmental contamination in the Turvo Limpo River basin which receives effluent discharges from domestic (residential and commercial) activities. The watercourses examined were the São Bartolomeu Stream, Turvo Sujo River, and Turvo Limpo River, located in the Minas Gerais State, Brazil. Water samples were collected at the river-side and analyzed for evaluation of pollutant inputs. The pH, temperature, electrical conductivity, redox potential (Eh), dissolved oxygen (DO), total and settleable solids, visual color, hardness, chemical oxygen demand (COD), biochemical oxygen demand (BOD), chloride, total phosphate, total nitrogen, ammonia nitrogen, nitrate, total coliforms and E. coli, as well as the Cd, Pb, Cu, and Zn speciation were determined in the watercourses. The data obtained were compared with those of the Brazilian Environmental Standards and with data from non-contaminated areas. River water characteristics in some sites were far from the limit values established for superficial waters with satisfactory quality. For instance, the BOD values reached 411 mg L(-1) for a maximum limit of 10.0 mg L(-1), while the ammonia nitrogen concentration reached 28 mg L(-1) for a maximum limit of 13.3 mg L(-1). Some sites showed E. coli values above those of non-contaminated regions. Besides the effects of sewage discharges into the water-courses, agriculture activities and the use of the area for cattle husbandry influenced the quality of the river waters, for instance, the pH of a spring-water sample reached the value of 4.3. The São Bartolomeu Stream has been contributing to the deterioration of the water quality of the Turvo Sujo River, while the Turvo Limpo River has also been affected by anthropogenic discharges in the Turvo Sujo River. The speciation of Cd, Cu and Pb showed that these metals were mainly found in the particulate fraction (i. e., associated with the suspended material). Fifty five percent of the water samples showed labile Zn concentrations greater than that of the nonlabile Zn.

Removal of Cu and Zn from swine raising wastewater using organic filters.

Rice husks, coffee bean skins, sugar cane bagasse, maize cobs, saw dust and fine charcoal dust were evaluated as filters for the removal of heavy metals (Cu and Zn) from the waste water of swine raising installations. The specific mass, pH and the sum of bases and removable acids were determined to characterize each of the filter materials. Each filtering material was placed in a 100 mm diameter, 600 mm long, PVC column to a height of 500 mm under 12,500 N m(-2) of compression. Chemical and physical analyses were determined on effluent samples collected for each 1.5 l up to a total of 15 l. The organic materials reduced the concentration of sediment solids (> 90%), total solids (up to 33%) and Cu (up to 43.6%) of the inffluent but had little or no effect on Zn concentration.

Assessment of water systems for contaminants from domestic and industrial sewages.

The State of Minas Gerais represents one of Brazil's most outstanding mining resources. The contamination of river water from kaolin processing activities may be harmful to people in the way of slow but chronic poisoning. On the other hand, the discharge of untreated or inadequately treated domestic sewage into aquatic environments can also cause deleterious effects to the health. However, no reliable figures are available for pollutant occurrences in river water. This draws attention to the very precarious situation that exists with respect to pollution by organic and inorganic toxic wastes, especially with respect to humans and fauna in all its expressions. Thus, with the purpose of establishing a preliminary report to trace out industrialisation outcomes, samples of river water, vegetation and fish were collected and analysed to detect pollutant inputs. The concentration of metals was determined in suspended particle, vegetation and fish, while those of nitrite, nitrate, phosphate and chloride were determined in river water samples. The concentration of dissolved oxygen (DO) was measured in river water at the time of collection. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were also determined. Metal inputs in the samples analysed appeared to be related to effluent discharges into the rivers. The suspended particles showed high concentrations (in mg kg(-1)) of zinc (62 600) and aluminium (559 000), while vegetation samples collected near rivers were heavily contaminated with iron (7680). The fishes examined were contaminated with chromium (1.5 mg kg(-1)). In general, the concentrations of nitrite, nitrate, chloride, phosphate and BOD in river water were lower than the maximum values established by the Brazilian Environmental Standards.

Mobility of heavy metals as related to soil chemical and mineralogical characteristics of Brazilian soils.

In order to better understand the relationship between soil characteristics and mobility of some heavy metals, correlation studies were conducted in samples of unlimed and limed A, B and C horizons of three Brazilian soils, representative of the majority of the tropical soils. A number of chemical and mineralogical characteristics of one Oxisol and two Ultisols were related to the retardation factors (Rf) for zinc (Zn), cadmium (Cd), copper (Cu) and lead (Pb). The retardation factors, obtained in leaching column experiments, were used as an estimate of solute movement in the profile. Soil types and soil horizons were found to influence metal retardation factors which, in turn, correlated better with the chemical than the mineralogical soil characteristics. For the unlimed soil samples, the soil characteristics that significantly correlated with Zn-Rf and Cd-Rf were the sum of exchangeable bases (SB), and soil exchangeable (Ca-KCl) and non-exchangeable (Ca-HCl) calcium contents. These results showed the strong influence of the cation exchange phenomenon on the retention and mobility of these two metals. For Cu and Pb, not only SB, cation exchange capacity (CEC) and Ca-KCl and Ca-HCl but also the organic matter correlated well with the Rf, showing that complex or chelate formation may play an important role in the movement of these elements. The important soil chemical characteristics related to the retardation factors in the limed soil samples were SB for Cd, and Ca-HCl for Cu and Pb, suggesting that precipitation may also influence the mobility and retention of the latter two heavy metals in these soil samples. Soil pH influenced the heavy metals adsorption and movement as shown by the significant correlation with the retardation factors when the combined data for the unlimed and limed soil samples was considered.