Steady-state design of vertical wells for liquids addition at bioreactor landfills

The rate at which liquids can be added to a vertical well, the lateral zone of impact of the well, and the liquids volume needed to wet the waste within the zone of impact of the well are the key inputs needed to design a vertical well system. This paper presents design charts that can be used to estimate these inputs as a function of municipal solid waste properties (porosity, hydraulic conductivity, and anisotropy ratio), well dimensions (radius and screen length), and injection pressure. SEEP/W modeling was conducted to estimate the key design inputs for a range of conditions practically encountered for a vertical well installed in landfilled waste. The flow rate, lateral zone of impact of a well, liquids volume added, and injection pressure were normalized with the waste properties and well dimensions to formulate dimensionless variables. A series of design charts were created to present dimensionless steady-state flow rate, lateral zone of impact, and the dimensionless liquid volume needed to reach a steady-state condition, as a function of dimensionless input variables. By using dimensionless variables formulated for this work, these charts permit the user to estimate the steady-state design variables described above for a wide range of configurations and conditions beyond those simulated without the need for further modeling. The results of the study suggest that the lateral extent of the well can be estimated using Darcy’s equation and assuming saturated unit-gradient vertical flow regime below the well bottom. An example problem is presented to illustrate the use of the design charts. The scenario described in the example problem was also modeled with SEEP/W, and the results were compared with those obtained from the design charts to demonstrate the validity of design charts for scenarios other than those used for the development of the design charts. The methodology presented in this paper should be thought of as a means to provide a set of bounds that an engineer can use along with their judgment in the design of a system for a specific site.     

Treatment of low-strength soluble wastewater using an anaerobic baffled reactor (ABR)

Treatment of low-strength soluble wastewater (COD approximately 500 mg/L) was studied using an eight chambered anaerobic baffled reactor (ABR). At pseudo steady-state (PSS), the average total and soluble COD values (COD(T) and COD(S)) at 8h hydraulic retention time (HRT) were found to be around 50 and 40 mg/L, respectively, while at 10h HRT average COD(T) and COD(S) values were of the order of 47 and 37 mg/L, respectively. COD and BOD (3 day, 27 degrees C) removal averaged more than 90%. Effluent conformed to Indian standards laid down for BOD (less than 30 mg/L). Reactor effluent characteristics exhibited very low values of standard deviation indicating excellent reactor stability at PSS in terms of effluent characteristics. Based on mass balance calculations, more than 60% of raw wastewater COD was estimated to be recovered as CH(4) in the gas phase. Compartment-wise profiles indicated that most of the BOD and COD got reduced in the initial compartments only. Sudden drop in pH (7.8-6.7) and formation of volatile fatty acids (VFA) (53-85 mg/L) were observed in the first compartment due to acidogenesis and acetogenesis. The pH increased and VFA concentration decreased longitudinally down the reactor. Residence time distribution (RTD) studies revealed that the flow pattern in the ABR was neither completely plug-flow nor perfectly mixed. Observations from scanning electron micrographs (SEM) suggest that distinct phase separation takes place in an ABR.     

Impact of urbanization on the groundwater regime in a fast growing city in central India

This paper describes the impact of urbanization on the groundwater regime in a fast growing city, Solapur, in central India, giving special emphasis on the management of the present and ultimate demand of water in 2,020 AD. The objective is to apprise the city planners and administrators of the effects of urbanization on the groundwater regime in a fast growing medium-sized city in a developing country where the infrastructure developments are not in conformity with the rapid growth in population. Solapur city with an area of 178.57 km2 receives a recharge of about 24 million m3 of groundwater from various sources annually. Reduction in recharge, as conventionally assumed due to the impact of urbanization, could not, however, be well established. Instead, there was a rise in recharge as water use in the city grew from time to time and more and more water was supplied to satisfy the human needs. Compared to mid-1970s, groundwater levels have increased within the main city area due to increased recharge and decreased groundwater abstraction. However, outside the main city area, there is a general decline in groundwater levels due to increased groundwater utilization for irrigation purposes. Groundwater quality deterioration has been highly localized. Water quality has deteriorated during the last 10 years, especially in dugwells, mainly due to misuse and disuse of these structures and poor circulation of groundwater. However, in case of borewells, comparison of the present water quality with that in mid-1970s and early 1980s does not show any perceptible change. Deeper groundwater tapped by borewells can still be used for drinking purposes with caution.     

Perceived Conflicts Between Pastoralism and Conservation of the Kiang Equus kiang in the Ladakh Trans-Himalaya, India

An emerging conflict with Trans-Himalayan pastoral communities in Ladakh’s Changthang Plateau threatens the conservation prospects of the kiang (Equus kiang) in India. It is locally believed that Changthang’s rangelands are overstocked with kiang, resulting in forage competition with livestock. Here, we provide a review and preliminary data on the causes of this conflict. Erosion of people’s tolerance of the kiang can be attributed to factors such as the loss of traditional pastures during an Indo-Chinese war fought in 1962, immigration of refugees from Tibet, doubling of the livestock population in about 20 years, and increasing commercialization of cashmere (pashmina) production. The perception of kiang overstocking appears misplaced, because our range-wide density estimate of 0.24 kiang km⁻² (± 0.44, 95% CL) is comparable to kiang densities reported from Tibet. A catastrophic decline during the war and subsequent recovery of the kiang population apparently led to the overstocking perception in Ladakh. In the Hanle Valley, an important area for the kiang, its density was higher (0.56 km⁻²) although even here, we estimated the total forage consumed by kiang to be only 3–4% compared to 96–97% consumed by the large livestock population (78 km⁻²). Our analysis nevertheless suggests that at a localized scale, some herders do face serious forage competition from kiang in key areas such as moist sedge meadows, and thus management strategies also need to be devised at this scale. In-depth socioeconomic surveys are needed to understand the full extent of the conflicts, and herder-centered participatory resolution needs to be facilitated to ensure that a sustainable solution for livelihoods and kiang conservation is achieved.     

NUMERICAL TECHNIQUES APPLIED TO PARTICLE DEPOSITION DURING SLOT FLOW1

ABSTRACT A mathematical model is presented of the process of particle sedimentation from a fluid-solid slurry while flowing through a vertical slot. The differential equations describing the process consist of 1st order, non-linear, partial differential equation and a 1st order, ordinary differential equation. These two equations have been solved using a forward difference technique. Results for typical sets of system parameters are presented and discussed. The model finds practical application to solid-waste disposal processes and to petroleum reservoir stimulation processes.     

Safety evaluation of joint and conventional lane merge configurations for freeway work zones

Inefficient operation of traffic in work zone areas not only leads to an increase in travel time delays, queue length, and fuel consumption but also increases the number of forced merges and roadway accidents. This study evaluated the safety performance of work zones with a conventional lane merge (CLM) configuration in Louisiana. Analysis of variance (ANOVA) was used to compare the crash rates for accidents involving fatalities, injuries, and property damage only (PDO) in each of the following 4 areas: (1) advance warning area, (2) transition area, (3) work area, and (4) termination area. The analysis showed that the advance warning area had higher fatality, injury, and PDO crash rates when compared to the transition area, work area, and termination area. This finding confirmed the need to make improvements in the advance warning area where merging maneuvers take place. Therefore, a new lane merge configuration, called joint lane merge (JLM), was proposed and its safety performance was examined and compared to the conventional lane merge configuration using a microscopic simulation model (VISSIM), which was calibrated with real-world data from an existing work zone on I-55 and used to simulate a total of 25 different scenarios with different levels of demand and traffic composition. Safety performance was evaluated using 2 surrogate measures: uncomfortable decelerations and speed variance. Statistical analysis was conducted to determine whether the differences in safety performance between both configurations were significant. The safety analysis indicated that JLM outperformed CLM in most cases with low to moderate flow rates and that the percentage of trucks did not have a significant impact on the safety performance of either configuration. Though the safety analysis did not clearly indicate which lane merge configuration is safer for the overall work zone area, it was able to identify the possibly associated safety changes within the work zone area under different traffic conditions.     

High CO<Subscript>2</Subscript> absorption of <Emphasis Type="Italic">O</Emphasis>-carboxymethylchitosan synthesised from chitosan

CO₂ absorption by liquid-containing amines to form carbamate and bicarbonates is an effective method of CO₂ mitigation from industrial exhausts, but this process is expensive and requires large quantities of amines. Here we modified chitosan, a naturally occurring biopolymer containing NH₂ functions, to use it for CO₂ absorption in aqueous media. Chitosan was dispersed in 40% aqueous NaOH solution then treated with monochloroacetic acid dissolved in isopropanol, to yield O-carboxymethylchitosan. Results show that the CO₂ absorption capacity of O-carboxymethylchitosan is 0.508 g/g, which is higher than the capacity of conventional amines such as 1-aminoamine, 2-methylpropanolamine and methyldiethanol amine, but lower than the capacity of monoethanolamine. A cyclic study showed that O-carboxymethylchitosan is a stable component for CO₂ absorption and regeneration.     

Effect of trichloroethylene (TCE) inhalation on biotransformation enzymes of rat lung and liver

Trichloroethylene (TCE) is widely used as an industrial solvent and cleaning fluid. In the present study the toxic effects of TCE inhalation on pulmonary and hepatic biotransformation enzymes in rats have been investigated by assay of aniline hydroxylase (AH), aminopyrine-N-demethylase (APD), benzo-a-pyrene hydroxylase (BH) and glutathione-s-transferase (GST) activities and glutathione (GSH) contents in liver as well as lungs of exposed animals. In both organs phase I and phase II drug metabolizing enzymes have been found to be increased along with decrease in GSH contents following TCE inhalation. Pulmonary as well as hepatic MFO's seem to be activated by inhaled TCE probably in an attempt for its rapid detoxification and reduced glutathione is used during its biotransformation.     

Evaluation of organochlorine insecticide residue levels in locally marketed vegetables of Jaipur City,Rajasthan, India

Considerable quantities of organochlorine insecticides are still used worldwide and their persistent residues are widely distributed throughout the environment. Various researchers from different parts of India and abroad have highlighted the extent of pollution caused by these insecticides. In view of the above facts the present study was conducted during 1993-1996 to investigate the magnitude of contamination of organochlorine insecticides in vegetables which were brought for sale to the consumers in the local markets of Jaipur city, Rajasthan, India. Samples of vegetables (potato, tomato, cabbage, cauliflower, spinach and okra) were collected at beginning, middle and end of the seasons with respect to different vegetables and organochlorine levels were assessed using Gas Liquid Chromatograph (GLC) equipped with Electron Capture Detector (ECD). Most of the collected samples were found to be contaminated with residues of DDT and its metabolites (DDD, DDE) isomers of HCH (alpha,beta and gamma-HCH), heptachlor, heptachlor epoxide and aldrin. Some of the detected insecticides exceeded the limit of tolerance prescribed by WHO/FAO.