Crash data analysis: collective vs. individual crash level approach

INTRODUCTION: Traffic safety literature has traditionally focused on identification of location profiles where "more crashes are likely to occur" over a period of time. The analysis involves estimation of crash frequency and/or rate (i.e., frequency normalized based on some measure of exposure) with geometric design features (e.g., number of lanes) and traffic characteristics (e.g., Average Annual Daily Traffic [AADT]) of the roadway location. In the recent past, a new category of traffic safety studies has emerged, which attempts to identify locations where a "crash is more likely to occur." The distinction between the two groups of studies is that the latter group of locations would change based on the varying traffic patterns over the course of the day or even within the hour. METHOD: Hence, instead of estimation of crash frequency over a period of time, the objective becomes real-time estimation of crash likelihood. The estimation of real-time crash likelihood has a traffic management component as well. It is a proactive extension to the traditional approach of incident detection, which involves analysis of traffic data recorded immediately after the incident. The units of analysis used in these studies are individual crashes rather than counts of crashes. RESULTS: In this paper, crash data analysis based on the two approaches, collective and at individual crash level, is discussed along with the advantages and shortcomings of the two approaches.     

Catalytic wet oxidation of the pretreated synthetic pulp and paper mill effluent under moderate conditions

In the present study, catalytic wet oxidation (CWO) was investigated for the destruction of organic pollutants in the thermally pretreated effluent from a pulp and paper mill under moderate temperature and pressure conditions. The thermal pretreatment studies were conducted at atmospheric pressure and 368K using copper sulfate as a catalyst. The thermal pretreatment reduced COD by about 61%. The filtrate of the thermal pretreatment step was used at pH 8.0 for CWO at 383-443K temperature and a total pressure of 0.85MPa for 4h. Catalysts used for the reaction include copper sulfate, 5% CuO/95% activated carbon, 60% CuO/40% MnO(2), and 60% CuO/40% CeO(2). Maximum COD reduction was found to be 89% during CWO step using 5% CuO/95% activated carbon with a catalyst loading of 8gl(-1) at 443K and 0.85MPa total pressure. Overall COD reduction for the pretreatment and the CWO was found to be 96%. Besides this, 60% CuO/40% CeO(2) catalyst also exhibited the similar activity as that of obtained with 5% CuO/95% activated carbon catalyst at 423K temperature and 0.85MPa total pressure. The pH of the solution during the experimental runs decreases initially due to the formation of carboxylic acid and then increases due to the decomposition of acids.     

Dissolution of steel slags in aqueous media

Environmental Science and Pollution Research - Steel slag is a major industrial waste in steel industries, and its dissolution behavior in water needs to be characterized in the larger context of...     

Start-up of sequencing batch reactor with <Emphasis Type="Italic">Thiosphaera pantotropha</Emphasis> for treatment of high-strength nitrogenous wastewater and sludge characterization

Biological treatment of high-strength nitrogenous wastewater is challenging due to low growth rate of autotrophic nitrifiers. This study reports bioaugmentation of Thiosphaera pantotropha capable of simultaneously performing heterotrophic nitrification and aerobic denitrification (SND) in sequencing batch reactors (SBRs). SBRs fed with 1:1 organic-nitrogen (N) and NH₄ ⁺-N were started up with activated sludge and T. pantotropha by gradual increase in N concentration. Sludge bulking problems initially observed could be overcome through improved aeration and mixing and change in carbon source. N removal decreased with increase in initial nitrogen concentration, and only 50–60 % removal could be achieved at the highest N concentration of 1000 mg L^?1 at 12-h cycle time. SND accounted for 28 % nitrogen loss. Reducing the settling time to 5–10 min and addition of divalent metal ions gradually improved the settling characteristics of sludge. Sludge aggregates of 0.05–0.2 mm diameter, much smaller than typical aerobic granules, were formed and progressive increase in settling velocity, specific gravity, Ca²⁺, Mg²⁺, protein, and polysaccharides was observed over time. Granulation facilitated total nitrogen (TN) removal at a constant rate over the entire 12-h cycle and thus increased TN removal up to 70 %. Concentrations of NO₂ ^?-N and NO₃ ^?-N were consistently low indicating effective denitrification. Nitrogen removal was possibly limited by urea hydrolysis/nitrification. Presence of T. pantotropha in the SBRs was confirmed through biochemical tests and 16S rDNA analysis.     

Ecosystem studies on upper region of Ganga River,India

A multi-disciplinary research programme on the Ganga River Ecosystem was launched by the Government of India in 1983 to collect information on its attributes. Monitoring of the initial 509 km unpolluted and unmonitored region of the river falling in partly mountainous and partly upper plain stretches for two years revealed good water quality. The Song River (a tributary) catchment, a victim of extensive mining activity in the past, was found to add maximum mineral load. The Bhagirathi River was found to carry maximum suspended solid load. Organic pollution was low throughout, occasionally showing seasonal and local peaks. The river exhibited a high oxidative state with pH falling in a slightly alkaline range and nutrient levels being very low.Diatoms formed a major part of the encountered genera of phytoplankton. Zooplankton were mainly represented by protozoans. Saprophytic bacteria underwent large spatial and temporal fluctuations. Coliforms exhibited an increasing trend with downstream river distance. The source of pollution could not be specifically characterized from an FC/FS ratio. Only one sample tested positive for enteric virus. The forms of benthic macroinvertebrates indicated a clean stream environment. It was observed that diversity indices, together with evenness and community comparison, could provide a promising approach to determine the state of the community.Eight heavy metals investigated, Cu, Zn, Fe, Cd, Mn, Pb, Ni and Co, were found to be present in the river water and bed sediments. The prominent mode of metal transport was found to be via the suspended load. The concentration of dissolved metals was found within WHO permissible limits. The heavy metal status of the Ganga River was compared with other rivers of the world. Sorptive properties of sediments were found to be similar to the general sorptive behaviour of the clays. Laboratory studies exhibited reasonable short t ₉₀ values for coliform survival in Ganga water. Faecal streptococcus survived longer.     

Morphological and Biochemical Characteristics of Avian Faecal Droppings and Their Impact on Survival of Avian Influenza Virus

Environmental specimens such as faecal droppings are considered important for the detection of avian influenza viruses (AIV). In view of lower rates of AIV isolation from avian faecal droppings, characterization of droppings is imperative to elucidate contributing factors. However, there are no reports on morphological and biochemical characteristics of droppings. The objective of the present study was the characterization of droppings from different avian species and their impact on the AIV detection and isolation. A total of 373 droppings belonging to 61 avian species from 22 families of apparently healthy wild migratory, resident, domestic birds and poultry were studied during five winter migratory bird seasons between 2007 to 2012 and 2016–2017. The colour, morphology and size of the droppings varied from species-to-species. These data could be useful for the identification of avian species. Droppings from 67% of the avian species showed acidic pH (4.5–6.5); nine species showed neutral pH (7.0), and 11 species showed alkaline pH (7.5). The infectious titers of AIV in droppings with acidic pH were significantly lower (p < 0.05) than those of the droppings with neutral and alkaline pH. However, acidic pH did not hamper AIV detection by real-time RT-PCR. In order to avoid the impact of acidic pH, collecting fresh droppings into viral transport medium (pH 7.0–7.5) would help improve the rate of AIV isolation.     

Characterization of value-added chemicals derived from the thermal hydrolysis and wet oxidation of sewage sludge

• Hydrothermal treatment can greatly improve resource recovery from sewage sludge. • tCOD removal during WO was ~55% compared with ~23% after TH. • TOC solubilization during hydrothermal treatment followed first-order kinetics. • Solids and carbon balance confirmed loss of organics during thermal hydrolysis. • Reaction pathways for thermal hydrolysis and wet oxidation are proposed. We evaluated the effect of hydrothermal pretreatments, i.e., thermal hydrolysis (TH) and wet oxidation (WO) on sewage sludge to promote resource recovery. The hydrothermal processes were performed under mild temperature conditions (140°C–180°C) in a high pressure reactor. The reaction in acidic environment (pH= 3.3) suppressed the formation of the color imparting undesirable Maillard’s compounds. The oxidative conditions resulted in higher volatile suspended solids (VSS) reduction (~90%) and chemical oxygen demand (COD) removal (~55%) whereas TH caused VSS and COD removals of ~65% and ~27%, respectively at a temperature of 180°C. During TH, the concentrations of carbohydrates and proteins in treated sludge were 400–1000 mg/L and 1500–2500 mg/L, respectively. Whereas, WO resulted in solids solubilization followed by oxidative degradation of organics into smaller molecular weight carboxylic acids such as acetic acid (~400–500 mg/L). Based on sludge transformation products generated during the hydrothermal pretreatments, simplified reaction pathways are predicted. Finally, the application of macromolecules (such as proteins), VFAs and nutrients present in the treated sludge are also discussed. The future study should focus on the development of economic recovery methods for various value-added compounds.     

Geochemical evaluation and human health risk assessment of nitrate-contaminated groundwater in an industrial area of South India

Environmental Science and Pollution Research - The primary goal of this study is to evaluate the groundwater quality and conduct a non-carcinogenic risk assessment of nitrate contamination in an...     

A semi-coupled model for determining the distribution of two-dimensional coherent structures in open channel flow

Environmental Fluid Mechanics - Mixing layers and associated large-scale turbulent structures are some of the most common features of turbulent shallow water flow. Due to their...