Engineered nanoparticles in wastewater and wastewater sludge – Evidence and impacts

Nanotechnology has widespread application in agricultural, environmental and industrial sectors ranging from fabrication of molecular assemblies to microbial array chips. Despite the booming application of nanotechnology, there have been serious implications which are coming into light in the recent years within different environmental compartments, namely air, water and soil and its likely impact on the human health. Health and environmental effects of common metals and materials are well-known, however, when the metals and materials take the form of nanoparticles – consequential hazards based on shape and size are yet to be explored. The nanoparticles released from different nanomaterials used in our household and industrial commodities find their way through waste disposal routes into the wastewater treatment facilities and end up in wastewater sludge. Further escape of these nanoparticles into the effluent will contaminate the aquatic and soil environment. Hence, an understanding of the presence, behavior and impact of these nanoparticles in wastewater and wastewater sludge is necessary and timely. Despite the lack of sufficient literature, the present review attempts to link various compartmentalization aspects of the nanoparticles, their physical properties and toxicity in wastewater and wastewater sludge through simile drawn from other environmental streams.     

Performance of a low cost MBT prior to landfilling: study of the biological treatment of size reduced MSW without mechanical sorting

In France, the interest in Mechanical Biological Treatment (MBT) prior to landfilling is actually growing. In the absence of acceptance criteria for the waste to be landfilled, an alternative to the intensive, high-technology MBT can only find its place in the French context if it shows substantial benefits from an environmental, economic or operational point of view. This paper presents an experiment of low-cost MBT of size reduced MSW without material splitting. The performance of an experimental, pilot-scale mechanical and biological treatment process has been studied on 37.5 Mg of raw municipal solid waste. The mechanical process has been kept simple with only coarse shredding and no material recovery. The biological treatment, which was a low-cost forced aeration process, was monitored for 25 weeks. The biogas production potential of the waste was reduced by 90% to 19 NL kgDM(-1). The initial AT4 index of 82.9 mg O2 gDM(-1) decreased to 16.0 mg O2 gDM(-1). After 25 weeks of aerobic treatment, the dry mass loss reached 37%, while the mass of waste going to landfill was reduced by 28%. The average performances of the process were explained by the biological process itself, which was not optimal, and also by the characteristics of the input waste. The high particle size of the treated waste and the high content of slowly biodegradable matter (such as paper and cardboard) may both be significant drawbacks for the biological stabilisation of waste.     

In situ ammonia removal in bioreactor landfill leachate

Although bioreactor landfills have many advantages associated with them, challenges remain, including the persistence of NH(3)-N in the leachate. Because NH(3)-N is both persistent and toxic, it will likely influence when the landfill is biologically stable and when post-closure monitoring may end. An in situ nitrogen removal technique would be advantageous. Recent studies have shown the efficacy of such processes; however, they are lacking the data required to enable adequate implementation at field-scale bioreactor landfills. Research was conducted to evaluate the kinetics of in situ ammonia removal in both acclimated and unacclimated wastes to aid in developing guidance for field-scale implementation. Results demonstrate that in situ nitrification is feasible in an aerated solid waste environment and that the potential for simultaneous nitrification and denitrification (even under low biodegradable C:N conditions) in field-scale bioreactor landfills is significant due to the presence of both aerobic and anoxic areas. All rate data fit well to Monod kinetics, with specific rates of removal of 0.196 and 0.117 mgN/day-g dry waste and half-saturation constants of 59.6 and 147 mgN/L for acclimated and unacclimated wastes, respectively. Although specific rates of ammonia removal in the unacclimated waste are lower than in the acclimated waste, a relatively quick start-up of ammonia removal was observed in the unacclimated waste. Using the removal rate expressions developed will allow for estimation of the treatment times and volumes necessary to remove NH(3)-N from recirculated landfill leachate.     

A Quantitative Tool for Assessing the Integrity of Southern Coastal California Streams

We developed a benthic macroinvertebrate index of biological integrity (B-IBI) for the semiarid and populous southern California coastal region. Potential reference sites were screened from a pool of 275 sites, first with quantitative GIS landscape analysis at several spatial scales and then with local condition assessments (in-stream and riparian) that quantified stressors acting on study reaches. We screened 61 candidate metrics for inclusion in the B-IBI based on three criteria: sufficient range for scoring, responsiveness to watershed and reach-scale disturbance gradients, and minimal correlation with other responsive metrics. Final metrics included: percent collector-gatherer + collector-filterer individuals, percent noninsect taxa, percent tolerant taxa, Coleoptera richness, predator richness, percent intolerant individuals, and EPT richness. Three metrics had lower scores in chaparral reference sites than in mountain reference sites and were scored on separate scales in the B-IBI. Metrics were scored and assembled into a composite B-IBI, which was then divided into five roughly equal condition categories. PCA analysis was used to demonstrate that the B-IBI was sensitive to composite stressor gradients; we also confirmed that the B-IBI scores were not correlated with elevation, season, or watershed area. Application of the B-IBI to an independent validation dataset (69 sites) produced results congruent with the development dataset and a separate repeatability study at four sites in the region confirmed that the B-IBI scoring is precise. The SoCal B-IBI is an effective tool with strong performance characteristics and provides a practical means of evaluating biotic condition of streams in southern coastal California.