The efficiency of electrocoagulation in treating wastewater from a dairy industry, part I: iron electrodes

Iron electrodes were used for electrocoagulation (EC) treatment of wastewater from a dairy plant. Electrolysis time, pH, current density and distance between electrodes were considered to assess the removal efficiency of chemical oxygen demand (COD), total solids (TS) and their fractions and turbidity. Samples were collected from the effluent of a dairy plant using a sampling methodology proportional to the flow. The treatments were applied according to design factorial of half fraction with two levels of treatments and three repetitions at the central point. The optimization of parameters for treating dairy industry effluent by electrocoagulation using iron electrodes showed that electric current application for 15 minutes, an initial sample pH close to neutral (pH 7.0) and a current density of 50 A (.)(m-2) resulted in a significant reduction in COD by 58 %; removal of turbidity, suspended solids and volatile suspended solids by 95 %; and a final treated effluent pH of approximately 9.5. Negative consequences of the type of electrode used were the emergence of an undesirable color and an increase in the proportion of dissolved solids in the treated effluent.     

Analysing the fate of nanopesticides in soil and the applicability of regulatory protocols using a polymer-based nanoformulation of atrazine

For the first time, regulatory protocols defined in the OECD guidelines were applied to determine the fate properties of a nanopesticide in two agricultural soils with contrasting characteristics. The nanoformulation studied had no effect on the degradation kinetics of atrazine indicating that (1) the release of atrazine from the polymer nanocarriers occurred rapidly relative to the degradation kinetics (half-lives 36–53 days) and/or that (2) atrazine associated with the nanocarriers was subject to biotic or abiotic degradation. Sorption coefficients, derived from a batch and a centrifugation technique at a realistic soil-to-solution ratio, were higher for the nanoformulated atrazine than for the pure active ingredient. Results indicate that the nanoformulation had an effect on the fate of atrazine. However, since the protocols applied were designed to assess solutes, conclusions about the transport of atrazine loaded onto the nanocarriers should be made extremely cautiously. The centrifugation method applied over time (here over 7 days) appears to be a useful tool to indirectly assess the durability of nanopesticides under realistic soil-to-solution ratios and estimate the period of time during which an influence on the fate of the active ingredient may be expected. More detailed investigations into the bioavailability and durability of nanopesticides are necessary and will require the development of novel methods suitable to address both the “nano” and “organic” characteristics of polymer-based nanopesticides.     

Global distribution of a key trophic guild contrasts with common latitudinal diversity patterns

Most hypotheses explaining the general gradient of higher diversity toward the equator are implicit or explicit about greater species packing in the tropics. However, global patterns of diversity within guilds, including trophic guilds (i.e., groups of organisms that use similar food resources), are poorly known. We explored global diversity patterns of a key trophic guild in stream ecosystems, the detritivore shredders. This was motivated by the fundamental ecological role of shredders as decomposers of leaf litter and by some records pointing to low shredder diversity and abundance in the tropics, which contrasts with diversity patterns of most major taxa for which broad-scale latitudinal patterns haven been examined. Given this evidence, we hypothesized that shredders are more abundant and diverse in temperate than in tropical streams, and that this pattern is related to the higher temperatures and lower availability of high-quality leaf litter in the tropics. Our comprehensive global survey (129 stream sites from 14 regions on six continents) corroborated the expected latitudinal pattern and showed that shredder distribution (abundance, diversity and assemblage composition) was explained by a combination of factors, including water temperature (some taxa were restricted to cool waters) and biogeography (some taxa were more diverse in particular biogeographic realms). In contrast to our hypothesis, shredder diversity was unrelated to leaf toughness, but it was inversely related to litter diversity. Our findings markedly contrast with global trends of diversity for most taxa, and with the general rule of higher consumer diversity at higher levels of resource diversity. Moreover, they highlight the emerging role of temperature in understanding global patterns of diversity, which is of great relevance in the face of projected global warming.     

A decision-support system in ICZM for protecting the ecosystems: integration with the habitat directive

This paper describes a decision-support system based on landscape ecology and focused on the study of ecosystems’ health. System capabilities are illustrated with three cases of integrated coastal zone management (ICZM), in the Adriatic Sea (Italy): the lagoon of Venice and the Rimini and Ancona coastal areas. Indicators and indices are developed with a focus on sub-regional and local problems in coastal management, with a multi-scale approach based on landscape and seascape ecology. Land-use changes of the coastal areas were detected by analyzing two sets of satellite images. Indices combining satellite imagery, socio-economic and environmental indicators, and landscape and seascape maps were created, showing ecological changes, habitat loss and gaps in conservation policy. The approach used provides means for the identification of conflicts and for the assessment of sustainability. Results show that the lagoon of Venice plays an important role in mitigating and compensating the impacts of human activities, and needs to be protected and restored. The Rimini area shows high ecological footprint and development-intensity and low biocapacity. The Ancona area needs the protection of its natural coastal space from potential sources of anthropogenic impacts to maintain its sustainability. A model of environment changes is critical for formulating effective environmental policies and management strategies. The developed decision-support system provides a suitability map per each area analyzed, which can be used in order to maximize different policy objectives and reduce coastal conflicts.     

Home economics in an oak gall: behavioural and chemical immune strategies against a fungal pathogen in Temnothorax ant nests

The Science of Nature - Orchids attach their pollinaria (cohesive masses of pollen) to specific body parts of flower visitors, but usually not to the hairy and scaly body parts of flower-visiting...     

New objective function for data reconciliation in water balance from industrial processes

The promotion of a better rational use of water in industry requires an adequate knowledge of aqueous streams inside industrial plants. The main difficulty found in this respect is a lack of accurate measurement of such streams. In order to overcome this difficulty, a water balance tool with data reconciliation is used. This paper presents a method based on the idea that an estimated assumption can be made for any flow rate based on the best available information (quality of information). The quality of information is inversely proportional to the uncertainty of the estimated or measured flow rate and therefore there is a proportionality constant that relates these two. This paper demonstrates that the values of the proportionality constants in the real system are proximally the same for any stream. Furthermore, the proposed method has been applied to real systems with very poor measurement. This method enables the data reconciliation from water balances without data redundancy and without having to ignore flow rates with high levels of uncertainty.     

Reduced riparian zone width compromises aquatic macroinvertebrate communities in streams of southern Brazil

Recent changes in Brazilian legislation reduced the width of riparian forest buffer needed to be preserved in private properties from 30 to 15 m or less. The consequences of these modifications can be dramatic, mainly because riparian buffer width is an important parameter for riparian forest structure and functioning. Our study assessed whether (1) macroinvertebrate family richness and Ephemeroptera, Plecoptera, and Trichoptera (EPT) family richness decrease with reduced riparian buffer width; (2) taxonomic composition and functional feeding group (FFG) composition of macroinvertebrates vary with a reduced riparian buffer width; and (3) reduced riparian buffer width similarly influence the macroinvertebrate community in different stream substrates. We selected three fragments with different riparian buffer widths (>40, <30, and <15 m) in three streams (fourth and fifth orders) in the Sinos River watershed, southern Brazil. Our results show that on all substrate types, reducing the width of the riparian buffer altered neither the macroinvertebrate richness nor EPT richness. However, EPT richness was greater in the substrates stone and gravel than leaf litter, independent of riparian buffer width. There was a significant difference in macroinvertebrate composition among riparian buffer widths. The macroinvertebrate composition and FFG differed among substrates, independent of riparian buffer width. This study showed that riparian buffer widths <15 m altered the macroinvertebrate community. A width greater than 15 m is necessary to maintain the composition and trophic conditions of macroinvertebrate families similar to those found in reference states of conservation.     

On the performance of Fe and Fe,F doped Ti-Pt/PbO2 electrodes in the electrooxidation of the Blue Reactive 19 dye in simulated textile wastewater

The electrochemical performance of pure Ti–Pt/β-PbO₂ electrodes, or doped with Fe and F (together or separately), in the oxidation of simulated wastewaters containing the Blue Reactive 19 dye (BR-19), using a filter-press reactor, was investigated and then compared with that of a boron-doped diamond electrode supported on a niobium substrate (Nb/BDD). The electrooxidation of the dye simulated wastewater (volume of 0.1 l, with a BR-19 initial concentration of 25 mg l⁻¹) was carried out under the following conditions: current density of 50 mA cm⁻², volume flow rate of 2.4 l h⁻¹, temperature of 25 °C and electrode area of 5 cm². The performances of the electrodes in the dye decolorization were quite similar, achieving 100% decolorization, and in some cases 90% decolorization was achieved by applying only ca. 0.3 A h l⁻¹ (8 min of electrolysis). The reduction of the simulated wastewater organic load, monitored by its total organic carbon content (TOC), was greater for the Ti–Pt/β-PbO₂–Fe,F electrode obtained from an electrodeposition bath containing 1 mM Fe³⁺ and 30 mM F⁻. In this case, after 2 h of electrolysis the obtained TOC reduction was 95%, while for the pure β-PbO₂ and the Nb/BDD electrodes the reductions were 84% and 82%, respectively.