Transport of oxytetracycline,chlortetracycline, and ivermectin in surface runoff from irrigated pasture

The transport of oxytetracycline, chlortetracycline, and ivermectin from manure was assessed via surface runoff on irrigated pasture. Surface runoff plots in the Sierra Foothills of Northern California were used to evaluate the effects of irrigation water application rates, pharmaceutical application conditions, vegetative cover, and vegetative filter strip length on the pharmaceutical discharge in surface runoff. Experiments were designed to permit the maximum potential transport of pharmaceuticals to surface runoff water, which included pre-irrigation to saturate soil, trimming grass where manure was applied, and laying a continuous manure strip perpendicular to the flow of water. However, due to high sorption of the pharmaceuticals to manure and soil, less than 0.1% of applied pharmaceuticals were detected in runoff water. Results demonstrated an increase of pharmaceutical transport in surface runoff with increased pharmaceutical concentration in manure, the concentration of pharmaceuticals in runoff water remained constant with increased irrigation flow rate, and no appreciable decrease in pharmaceutical runoff was produced with the vegetative filter strip length increased from 30.5 to 91.5 cm. Most of the applied pharmaceuticals were retained in the manure or within the upper 5 cm of soil directly beneath the manure application sites. As this study evaluated conditions for high transport potential, the data suggest that the risk for significant chlortetracycline, oxytetracycline, and ivermectin transport to surface water from cattle manure on irrigated pasture is low.     

Powdered activated carbon coupled with enhanced coagulation for natural organic matter removal and disinfection by-product control: application in a Western Australian water treatment plant

The removal of organic precursors of disinfection by-products (DBPs), i.e. natural organic matter (NOM), prior to disinfection and distribution is considered as the most effective approach to minimise the formation of DBPs. This study investigated the impact of the addition of powdered activated carbon (PAC) to an enhanced coagulation treatment process at an existing water treatment plant on the efficiency of NOM removal, the disinfection behaviour of the treated water, and the water quality in the distribution system. This is the first comprehensive assessment of the efficacy of plant-scale application of PAC combined with enhanced coagulation on an Australian source water. As a result of the PAC addition, the removal of NOM improved by 70%, which led to a significant reduction (80-95%) in the formation of DBPs. The water quality in the distribution system also improved, indicated by lower concentrations of DBPs in the distribution system and better maintenance of disinfectant residual at the extremities of the distribution system. The efficacy of the PAC treatment for NOM removal was shown to be a function of the characteristics of the NOM and the quality of the source water, as well as the PAC dose. PAC treatment did not have the capacity to remove bromide ion, resulting in the formation of more brominated DBPs. Since brominated DBPs have been found to be more toxic than their chlorinated analogues, their preferential formation upon PAC addition must be considered, especially in source waters containing high concentrations of bromide.     

Use of a column leaching test to study the mobility of chlorinated HOCs from a contaminated soil and the distribution of compounds between soluble and colloid phases

An equilibrium and recirculation column test for hydrophobic organic chemicals (ER-H test) was used to study the leaching behaviour of chlorophenols (CPs), polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) from contaminated soil. A 50% increase in the pore water velocity was shown to have little or no effect on the mobility of CPs, PCDEs, PCDFs and PCDDs. The standard deviations of truly dissolved compounds, CPs, were between 19% and 65% between the tests. However, the repeatability of the ER-H test decreased with increases in the hydrophobicity of the studied compounds; the standard deviations for PCDEs, PCDFs and PCDDs ranged from 53% to 110%, 57% to 77% and 110% to 130%, respectively. The influence of colloids on the release of these compounds was also examined. Up to 30% of the CPs in the soil were leached, of which 1-3% were associated with colloids. The PCDEs, PCDFs and PCDDs were found to be preferably associated with the particulate fraction of the leachate, and less than 0.2% of these compounds were mobilised.     

Changes in the microbial communities during co-composting of digestates

Anaerobic digestion is a waste treatment method which is of increasing interest worldwide. At the end of the process, a digestate remains, which can gain added value by being composted. A study was conducted in order to investigate microbial community dynamics during the composting process of a mixture of anaerobic digestate (derived from the anaerobic digestion of municipal food waste), green wastes and a screened compost (green waste/kitchen waste compost), using the COMPOCHIP microarray. The composting process showed a typical temperature development, and the highest degradation rates occurred during the first 14 days of composting, as seen from the elevated CO₂ content in the exhaust air. With an exception of elevated nitrite and nitrate levels in the day 34 samples, physical–chemical parameters for all compost samples collected during the 63 day process indicated typical composting conditions. The microbial communities changed over the 63 days of composting. According to principal component analysis of the COMPOCHIP microarray results, compost samples from the start of the experiment were found to cluster most closely with the digestate and screened compost samples. The green waste samples were found to group separately. All starting materials investigated were found to yield fewer and lower signals when compared to the samples collected during the composting experiment.     

Enabling Sustainable Agro-Food Futures: Exploring Fault Lines and Synergies Between the Integrated Territorial Paradigm,Rural Eco-Economy and Circular Economy

What kind of futures does agro-food imaginaries enable and who can get involved in the making of agro-food futures? In this respect, what can the increasingly influential idea of circular economy potentially offer in terms of enabling more sustainable agrofood futures? We approach this task by first outlining the interconnected challenges that the agro-food system is facing related to environmental degradation, economic crises and social problems. Then we consider the way these challenges are being addressed in agro-food studies. We argue that agro-food research in recent years has seen important contributions in relation to studies of alternative food networks and the “quality” turn. These research agendas have challenged the current logic of the food system in terms of offering alternative visions of future development. We highlight two examples from the literature—the eco-economy and the integrated territorial agri-food paradigm—that develop broader frameworks for rethinking the future of the agro-food system and which have distinguished themselves in contrast to the industrialized and globalized conventional food system. We find that with respect to reorienting and reconfiguring economic structures and relations all three approaches share a common goal, but circular economy stands out in relation to the actors that are included by, for example, emphasizing collaborations and partnerships with extant agro-food businesses. Also with regards to scalar politics, it would be prudent to consider the potentials offered by the increasingly influential ideas around circular economy.     

Climate change impact on water quality: model results from southern Sweden

Starting from six regional climate change scenarios, nitrogen leaching from arable-soil, water discharge, and nitrogen retention was modeled in the R?nne? catchment. Additionally, biological response was modeled in the eutrophic Lake Ringsj?n. The results are compared with similar studies on other catchments. All scenarios gave similar impact on water quality but varied in quantities. However, one scenario resulted in a different transport pattern due to less-pronounced seasonal variations in the hydrology. On average, the study shows that, in a future climate, we might expect: i) increased concentrations of nitrogen in the arable root zone (+50%) and in the river (+13%); ii) increased annual load of nitrogen from land to sea (+22%) due to more pronounced winter high flow; moreover, remote areas in the catchment may start to contribute to the outlet load; iii) radical changes in lake biochemistry with increased concentrations of total phosphorus (+50%), total nitrogen (+20%), and planktonic algae such as cyanobacteria (+80%).     

Modelling the motion of an internal solitary wave over a bottom ridge in a stratified fluid

A series of laboratory experiments has been carried out to investigate the passage of an internal solitary wave of depression over a bottom ridge, in a two-layer fluid system for which the upper and lower layer is linearly-stratified and homogeneous respectively. Density, velocity and vorticity fields induced by the wave propagation over the ridge have been measured simultaneously at three locations, namely upstream, downstream and over the ridge crest, for a wide range of model parameters. Results are presented to show that wave breaking may occur for a sufficiently large wave amplitude and a strong ridge blockage factor, with accompanying mixing and overturning. Density field data are presented (i) to illustrate the overturning and mixing processes that accompany the wave breaking and (ii) to quantify the degree of mixing in terms of the wave and ridge parameters. For weak encounters, good agreement is obtained between the laboratory experimental results (velocity and vorticity fields induced by the wave propagation) and the predictions of a recently-developed fully nonlinear theory. Discrepancies between theory and experiment are discussed for cases in which breaking and mixing occur.     

The use of urban clay-pit ponds for human recreation: assessment of impacts on water quality and phytoplankton assemblages

Artificially created ponds in urban areas may be important biodiversity refugia and may provide recreational services for populations. In order to obtain information on the seasonal development of the environmental conditions, water quality was determined in ten clay-pit ponds situated in the Austrian capital, Vienna. These ponds show high electrical conductivity (up to 3,000 μS cm^???1), indicating elevated levels of salinity, which can be attributed to the geological setting of the underground. Furthermore, the ponds experience a gradient from low to high human pressure resulting from recreational activities (swimming, fishing, urbanisation of the pond boundaries). Results obtained from multivariate statistics methods suggest that ponds were mainly structured by salinity and by algal biomass, which can be attributed to resource supply related with eutrophication. According to their water chemistry, the ponds were classified as meso- to hypereutrophic. Stoichiometric N/P ratios suggest that phytoplankton productivity in hypereutrophic ponds is nitrogen limited, whilst algae in ponds with lower trophic levels experience growth imitation by phosphorus depletion. We eventually related environmental conditions to algal species occurrences and developed a model for algal assemblages indicating the particular trophic state at different seasons.     

Bacterial removal and protozoan grazing in biological sand filters

The objective of the study was to investigate the importance of protozoan predation as a biological removal mechanism in sand filters used for purification of bacteria from wastewater. Eleven sand filter columns were seeded with a high dose of wastewater (70 mm d(-1)) and a high concentration (10(8) colony forming units [CFU] mL(-1)) of Aeromonas hydrophila (American Type Culture Collection [ATCC] 14715) for a period of 30 d. Water samples from three filter outlets were analyzed for the concentration of A. hydrophila. In addition, one filter column was sacrificed each sampling day for the quantification of A. hydrophila, culturable bacteria (heterotrophic plate counts, HPC), total bacterial counts, and protozoa in the sand. The mean removal efficiency of A. hydrophila in the sand filter columns was 4.7 log units. The concentration of A. hydrophila in the sand filter effluent, however, had a clearly time-dependent pattern from high (log 6) and unstable concentrations to low and more stable levels (log 2). The removal efficiency of A. hydrophila correlated significantly (P = 0.0005, r2 = 0.6) with numbers of protozoa in the sand filters. Significantly higher (P < 0.05) concentrations of A. hydrophila were observed in sand filter effluents from columns treated with the protozoan inhibitor cycloheximide, compared with nontreated columns. Results from the present study show that protozoan grazing plays an important role as a bacterial removal mechanism in sand infiltration systems.     

Organic chloramines in chlorine-based disinfected watersystems: A critical review

This paper is a critical review of current knowledge of organic chloramines in water systems,including their formation, stability, toxicity, analyticalmethods for detection, and their impact on drinking water treatment and quality. The term organic chloramines may refer to any halogenated organic compounds measured as part of combined chlorine (the difference between themeasured free and total chlorine concentrations), andmay include N-chloramines, N-chloramino acids, N-chloraldimines and N-chloramides. Organic chloramines can form when dissolved organic nitrogen or dissolved organic carbon react with either free chlorine or inorganic chloramines. They are potentially harmful to humans and may exist as an intermediate for other disinfection by-products. However, little information is available on the formation or occurrence of organic chloramines in water due to a number of challenges. One of the biggest challenges for the identification and quantification of organic chloramines in water systems is the lack of appropriate analytical methods. In addition, many of the organic chloramines that formduring disinfection are unstable,which results in difficulties in sampling and detection. To date research has focussed on the study of organic monochloramines. However, given that breakpoint chlorination is commonly undertaken in water treatment systems, the formation of organic dichloramines should also be considered. Organic chloramines can be formed frommany different precursors and pathways. Therefore, studying the occurrence of their precursors in water systems would enable better prediction and management of their formation.