Development of vermicast from sludge and powdered oyster shell

Soil acidification is one of the rising land degradation issues facing world agriculture. The risk of acidification is currently being assessed as part of agriculture productivity and sustainable theme. This study was conducted to produce a new vermicomposting cast as a recycling resource derived from municipal sewage sludge and waste oyster shell. The earthworm, Eisenia Andrei, was fed under different conditions. The most suitable mixture was 77:23 w/w% of sewage sludge and waste oyster shell. Powdered oyster shell (POS) sludge blend provided a stable pH, due to its buffering capacity during vermiculture because of the Ca²⁺ and OH^? release effect. The vermicast products fulfilled the cast standards of Korea Ministry of Environment for all the parameters such as moisture content, pH, salinity, organic carbon, TKN, Phosphate, and heavy metals. Slowly released organic matter when added to soil improves the capacity of the soil to hold nutrients for plants, improve soil aeration for roots, and improves soil drainage. This product will be an addition to already-commercialized sludge vermicast as a higher value product.     

A new approach to characterize biodegradation of organics by molecular mass distribution in landfill leachate

This study provides biodegradability of organics in leachate according to their molecular mass distributions (<0.5, 0.5 to 1, 1 to 3, 10, and >10 KDa). Organics with molecular mass values lower than 0.5 KDa were the predominant species in the raw leachate filtrate, and the aerated lagoon process was very effective in treating these highly biodegradable organics; the Fenton's oxidation process was very effective in treating not-so-biodegradable organics with molecular mass values higher than 0.5 KDa, but a portion of these organics were converted into organics <0.5 KDa after Fenton's oxidation. An oxygen uptake measurement using a respirometer was more sensitive than a conventional biochemical oxygen demand measurement to evaluate bioactivities, especially when bioactivities were low.     

Compartment model of aerobic and anaerobic biodegradation in a municipal solid waste landfill

The mathematical formulations in a one-dimensional compartment model of the biodegradation of organic landfill components are described. The model is designed to switch between anaerobic and aerobic conditions, depending on the local oxygen concentration. The model also includes the effect of environmental factors, such as moisture content, pH, and temperature, on reaction rates. The model includes not only biodegradation processes for carbon compounds (acetate, CO2, CH4), but also for nitrogen compounds involved in nitrification and denitrification due to their significance in landfills. Two example runs to simulate anaerobic and aerobic waste were conducted for a single landfill unit cell by changing the organic content and diffusion coefficient.     

Mini-review on river eutrophication and bottom improvement techniques,with special emphasis on the Nakdong River

Water quality in rivers is vital to humans and to maintenance of biotic and ecological integrity. During the Four Major Rivers restoration of South Korea, remarkable attempts have been made to decrease external nutrient loads and moveable weirs were designed to discharge silt that may deposit in pools. However, recently eutrophication of the Nakdong River, which was limited to the lower reaches, is seen to be spreading upstream. The reduction of external nutrient loads to rivers is a long-term goal that is unlikely to lead to reductions in algal blooms for many years because of the time required to implement effective land management strategies. It would therefore be desirable to implement complementary strategies. Regulating the amount of water released is effective at preventing algae blooms in weir pools; so, the relationship between discharge, stratification and bloom formation should be understood in this regard. However, pollutants are likely to accumulate in the riverbed upstream from release points. Thus, to control phosphorus levels, total phosphorus density should be lowered by applying in-river techniques as well. As many ecosystem properties are controlled by multiple processes, simultaneous river bottom improvement techniques, such as combined dissolved oxygen supply and nutrient inactivation, are likely to be effective. The purpose of this review is to present a series of technological approaches that can be used to improve the river bottom area and hence sediment nutrient release, and to illustrate the application of these techniques to the Nakdong River.     

Prediction of effluent concentration in a wastewater treatment plant using machine learning models

Of growing amount of food waste, the integrated food waste and waste water treatment was regarded as one of the efficient modeling method. However, the load of food waste to the conventional waste treatment process might lead to the high concentration of total nitrogen(T-N) impact on the effluent water quality. The objective of this study is to establish two machine learning models—artificial neural networks(ANNs) and support vector machines(SVMs), in order to predict 1-day interval T-N concentration of effluent from a wastewater treatment plant in Ulsan, Korea. Daily water quality data and meteorological data were used and the performance of both models was evaluated in terms of the coefficient of determination(R~2), Nash–Sutcliff efficiency(NSE), relative efficiency criteria(d rel). Additionally, Latin-Hypercube one-factor-at-a-time(LH-OAT) and a pattern search algorithm were applied to sensitivity analysis and model parameter optimization, respectively. Results showed that both models could be effectively applied to the 1-day interval prediction of T-N concentration of effluent. SVM model showed a higher prediction accuracy in the training stage and similar result in the validation stage.However, the sensitivity analysis demonstrated that the ANN model was a superior model for 1-day interval T-N concentration prediction in terms of the cause-and-effect relationship between T-N concentration and modeling input values to integrated food waste and waste water treatment. This study suggested the efficient and robust nonlinear time-series modeling method for an early prediction of the water quality of integrated food waste and waste water treatment process.     

Overtime work as the antecedent of employee satisfaction,firm productivity,and innovation

Overtime work has been blamed for the deterioration of employee satisfaction and productivity. However, the organization‐level implications of overtime work as a normative expectation remain unclear. In this study, such effects were analyzed through human capital theory and a causal attribution approach. Various organizational outcomes and boundary conditions were explored in explaining these implications. The analysis of time lagged data from 273 firms affirmed that a firm's overtime level was related negatively to employee satisfaction. However, it was positively related to the firm's productivity and curvilinearly (inverted U‐shaped) related to innovation. The effects of the firm's overtime level on firm productivity and innovation were also moderated by organizational trust. This study highlights the costs and benefits of overtime work as tools for utilizing human capital and reveals the critical contingency of organizational trust that enables firms to attenuate the costs of the overtime level and accentuate its potential benefits.     

Plant communities in relation to flooding and soil contamination in a lowland Rhine River floodplain

Using canonical correspondence analysis (CCA), relationships were investigated between plant species composition and flooding characteristics, heavy metal contamination and soil properties in a lowland floodplain of the Rhine River. Floodplain elevation and yearly average flooding duration turned out to be more important for explaining variation in plant species composition than soil heavy metal contamination. Nevertheless, plant species richness and diversity showed a significant decrease with the level of contamination. As single heavy metal concentrations seemed mostly too low for causing phytotoxic effects in plants, this trend is possibly explained by additive effects of multiple contaminants or by the concomitant influences of contamination and non-chemical stressors like flooding. These results suggest that impacts of soil contamination on plants in floodplains could be larger than expected from mere soil concentrations. In general, these findings emphasize the relevance of analyzing effects of toxic substances in concert with the effects of other relevant stressors.     

Carbonaceous species in fine particles at the background sites in Korea between 1994 and 1999

Organic carbon (OC) and elemental carbon (EC) in fine particles (PM_2.5) at two background sites, Kosan and Kangwha in Korea were measured during intensive field studies between 1994 and 1999. Fine particles were collected on pre-fired quartz filters in a low-volume sampler and analyzed using the selective thermal oxidation method with MnO₂ catalyst. The OC and EC concentrations at Kosan located at western tip of Cheju Island in southern Korea are lower than those at Kangwha located at western coastal area in mid-Korean peninsula. Still, the OC concentrations at Kosan are generally higher than those at other background areas in Japan and USA. The EC concentrations at Kosan are lower than or comparable to those at other background areas. The total carbon (TC, sum of OC and EC) to EC ratio values at both sites were higher than those at other background areas in Japan and USA. At Kosan, the OC and EC concentrations when air parcels were from southern China were higher than those when air parcels were coming from northern China. However, at Kangwha, the differences were statistically not clear since most air parcels were from northern China. Except when air parcels were from the North Pacific during summer, the OC and EC concentrations are well correlated indicating that both OC and EC share the same emission/transport characteristics. From the gaseous hydrocarbon data and the OC and EC relationship, it was found that during summer local biogenic emissions of OC might be significant at Kosan.