Properties of composts from household food waste produced in automatic composters.

The minimization of landfill deposition of waste containing biological components represents a big problem, especially in built-up residential areas. The main problem of biologically degradable municipal waste is the quantity and composition of household waste which can have an important influence on decomposition processes already in collecting vessels. An amount of household waste produced in residential areas in the Czech Republic varies from 31 to 337 g/person/day, with an average value of 250 g. Waste of plant material character is produced in the range from 22 to 291 g/person/day. Composts were prepared in the home composters from household food waste. After the end of the composting process, compost does not have the organic component sufficiently stabilized, which is documented by a high value of electrical conductivity of aqueous leachate reaching more than 4 mS/cm and low humification index. The value of the humification index pronouncedly increased after eight weeks from 0.05 to 0.85, while compost from composting of green waste using windrow system have humification index of 3.48. An aim of this work is the determination of properties of composts prepared from HFW in automatic composters and identification of differences compared with composts prepared from a mixture of biodegradable green waste.

Soil heavy metal pollution and risk assessment associated with the Zn-Pb mining region in Yunnan, Southwest China.

The environmental assessment and identification of sources of heavy metals in Zn-Pb ore deposits are important steps for the effective prevention of subsequent contamination and for the development of corrective measures. The concentrations of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in soils from 40 sampling points around the Jinding Zn-Pb mine in Yunnan, China, were analyzed. An environmental quality assessment of the obtained data was performed using five different contamination and pollution indexes. Statistical analyses were performed to identify the relations among the heavy metals and the pH in soils and possible sources of pollution. The concentrations of As, Cd, Pb, and Zn were extremely high, and 23, 95, 25, and 35% of the samples, respectively, exceeded the heavy metal limits set in the Chinese Environmental Quality Standard for Soils (GB15618-1995, grade III). According to the contamination and pollution indexes, environmental risks in the area are high or extremely high. The highest risk is represented by Cd contamination, the median concentration of which exceeds the GB15618-1995 limit. Based on the combination of statistical analyses and geostatistical mapping, we identified three groups of heavy metals that originate from different sources. The main sources of As, Cd, Pb, Zn, and Cu are mining activities, airborne particulates from smelters, and the weathering of tailings. The main sources of Hg are dust fallout and gaseous emissions from smelters and tailing dams. Cr and Ni originate from lithogenic sources.

Behavior of metals in a combined wastewater collection system in Ostrava, Czech Republic.

In combined wastewater collection systems, the concentrations of metals and the form of metal occurrence (dissolved form and bonding of metals to total suspended solids) influence the efficiency of capturing metals into sludge in wastewater treatment plants. The variability of metal concentrations was determined for 12 sampling sites during dry weather periods (DWP) and wet weather periods (WWP). Wastewater during DWP contain in dissolved form 77% of cadmium, 75% of nickel, 66% of arsenic, 57% of manganese and 50% of zinc and copper. Other metals are preferably bound to suspended particulates: 65% of chromium, iron, vanadium, mercury and 91% of lead. Comparison of metal concentrations in wastewater during DWP and WWP can be used to determine non-point source contributions. During WWP, metal concentrations increase by 24 to 25% for cadmium and zinc, 22% for nickel and 18% for copper. Urine and feces are responsible for a very small portion (<15%) of the total content of metals. Households are the main source of cadmium and copper (64% of total concentrations of these metals in wastewater).