Iranian Journal of Environmental Health Science and Engineering
Volume:3 Issue: 2, Spring 2006

The study reports the level of traffic-induced noise pollution in Sylhet City. For this purpose noise levels have been measured at thirty-seven major locations of the city from 7 am to 11 pm during the working days. It was observed that at all the locations the level of noise remains far above the acceptable limit for all the time. The noise level on the main road near residential area, hospital area and educational area were above the recommended level (65dBA). It was found that the predictive equations are in 60-70% correlated with the measured noise level. The study suggests that vulnerable institutions like school and hospital should be located about 60m away from the roadside unless any special arrangement to alleviate sound is used.

Upflow anaerobic sludge blanket (UASB) reactors have been widely used for treatment of industrial wastewater. In this study two full-scale UASB reactors were investigated. Volume of each reactor was 420 m3. Conventional parameters such as pH, temperature and efficiency of COD, BOD, TOC removal in each reactor were investigated. Also several initial parameters in designing and operating of UASB reactors, such as upflow velocity, organic loading rate (OLR) and hydraulic retention time were investigated. After modifying in operation conditions in UASB-2 reactor, average COD removal efficiency at OLR of 10–11 kg COD / m3 day was 55 percent. In order to prevent solids from settling, upflow velocity was increased to 0.35 m/h. Also to prevent solids from settling, the hydraulic retention time of wastewater in UASB-2 reactor was increased from 200 to 20 hours. This was expected that with good operation of UASB-2 reactor and with expanding of granules in the bed of the reactor, COD removal efficiency will be increased to more than 80 percent. But, because of deficiency on granulation and operation in UASB-2 reactor, this was not achieved. COD removal efficiency in the UASB-1 reactor was little. To enhance COD efficiency of UASB-1 reactor, several parameters were needed to be changed. These changes included enhancing of OLRs and upflow velocity, decreasing hydraulic retention time and operating with new sludge.

An aerated submerged fixed-film (ASFF) bioreactor was developed to treat an artificial wastewater based on crude oil. Bee-Cell 2000 was used as support media having porosity of 87% and a specific surface area of 650 m2/m3. The system was able to achieve 83.14–97.05 percentage removal efficiencies of soluble chemical oxygen demand (SCOD) in the organic loading rate range of 0.84 to 9.41 g SCOD/m2.day. Results showed that the effluent SCOD concentration ranged between 18.93 and 100.93 mg/L at organic loadings experienced. Therefore, an ASFF process showed that it was feasible to treat high oily wastewater in order to meet the discharge standards.

Investigation of the effectiveness of simultaneous adsorption and biodegradation (SAB) process over individual processes by using microbes Rhizopus oryzae and Stemphylium loti with granular activated carbon (GAC) as adsorbent was carried out. The maximum removal efficiency of cyanide had been achieved by biodegradation alone was 83% by R. oryzae, while it was 90% by S. loti at initial pH of 5.6 and 7.2 respectively and at initial CN- concentration of 150 mg/L. In the combined process efficiency of R. oryzae closer to S. loti (95.3% and 98.6% respectively)

The Cr (VI) adsorption characteristics of Ulmus leaves (UL) and their ash were examined as a function of contact time, initial pH, and initial metal ion concentration. Batch adsorption experiments were performed. The effects of Ca2+, Mg2+, Na+ and K+ on adsorption were studied. Maximum removal was achieved in the pH=7, contact time of 60 minutes and with initial Cr (VI) concentration of 2 mg/L. Because at pH ≥6.5, precipitation of chromium may take place, optimum pH was selected at 6. Maximum adsorption rate values were found at the first 60 min at pH= 6. The effect of the adsorbent on COD removal from aqueous solution showed that 2g/L of adsorbent caused 130 and 75 mg /L increase in COD of deionized water in 60 min for UL and its ash, respectively. The chromium adsorption data obtained under the optimum condition were described by the Langmuir and Freundlich isotherms. Studies showed that the Langmuir adsorption model better fitted than Freundlich, with R2 >0.99. Also UL ash was more efficient than living leaves in removing chromium from aqueous solution.

In this investigation, the efficacy of the herbicide butachlor, (N-butoxymethyl-2 chloro-21, 61 diethyl acetanilide) was tested against few common submerged macrophytes namely Hydrilla (Hydrilla verticillata (L.) Royale), Najas (Najas minor All.), Nechamandra (Nechamandra alternifolia (Roxb.) Thwaites) and Ottelia (Ottelia alismoides (L.) Pers.) of freshwater fish ponds. Almost complete decay of Hydrilla, Nechamandra and Ottelia was achieved at 7.5 L of active ingredient/ha/m butachlor within 15 days while the herbicide showed no negative effect on Najas. However at the same concentration of butachlor, total mortality of zooplankton and water fern Azolla (Azolla caroliniana Lamarck) occurred within seven days. In case of few freshwater fish species like Rohu (Labeo rohita), Channa (Channa punctatus), Anabas (Anabas testitudineus) and Heteropneustes (Heteropneustes fossilis), total mortality occurred upto 90 days after application of the same dose of butachlor but fish survived beyond 120 days of herbicide application indicating degradation of the herbicides.

Ultrasonic technology may be used for water and wastewater treatment as an advanced oxidation process. Application of this technology, leads to the decomposition of many organic compounds during cavitation process. In this study, the efficiency of ultrasonic in advanced treatment of municipal wastewater has been investigated by use of an ultrasonic bath. COD and BOD5 tests were used as the indicators of organic matter concentrations and three detention times for treatment were appointed at 10, 30 and 60 minutes. Two frequencies of 35 and 130 kHz for sonication were used. Results indicated that sonication can reduce 25% to 30% of COD in less than 60 minutes. Also, it was indicated that suspended COD was mainly converted to soluble COD during sonication. The rate of hydrogen peroxide production and thus the efficiency of treatment were higher at 130 kHz, but this efficiency was not much increased by prolonging sonication time. In other words, maximum efficiency was achieved at the initial time of sonication. Furthermore, no considerable change in nutrients concentration was detected and pH variations of samples were negligible (<0.3). In contrast, significant temperature change occured which was about (18-20)oC increase in 60 minutes. However, this temperature change had no considerable effect on treatment efficiency.

The treatment of methyl tertiary butyl ether (MTBE) vapors in biotrickling filters for air pollution control was investigated using different bacterial cultures. In the first phase, reactor was inoculated by the indigenous organisms and in the next phase, an aerobic microbial consortium able to biodegrade MTBE was used for reactor bed inoculation. Result was obtained only by specific organism: reactor was able to remove MTBE,after a short adaptation phase. Laboratory scale biotrickling filters were able to degrade up to 25 g/m.h with removal efficiency of 90%. They also showed a low rate of biomass accumulation.

This paper presents a statistical approach to estimating the effects of psychological factors on humans due to inappropriate waste disposal in the environment. Factorial experimental analysis is combined with the concepts of transition matrix and steady state conditions. An adequate understanding into the statistical quantification of the waste disposal concept would aid policy makers in effective decision making and the proper control of environment. The feasibility of developing statistical parameters for assessing the waste disposal concept is confirmed. The work shows the novelty of the approach.

A survey of medical waste management (MWM) practices and their implications to health and environment was carried out in metropolitan Lagos. Lagos is currently the most populous and urbanized city in the country with an estimated population of over 13 million people. The study assessed management practices in four (2 privates and 2 publics) hospitals ranging in capacity from 40 to 600 beds. Empirical data was obtained on medical waste generation, segregation, storage, collection, transportation and disposal. The observed MWM practices in all hospitals indicate absence of full compliance with the protocol for handling medical waste as stipulated in the relevant sections of the guidelines and standards for environmental pollution control in Nigeria. Three hospitals demonstrated high priority for segregation of infectious medical waste. Average generation rate of medical waste in the investigated hospitals ranged from 0.562 kg/bed.day to 0.670 kg/bed.day. Infectious waste accounts for between 26 to 37% of this volume. Only two of the hospitals investigated carry out treatment of their infectious and sharp waste types by incineration before final disposal. Burning and burial of medical waste is an unusual but common practice among the hospitals. All the hospitals employ the services of the state owned solid waste management company, the Lagos State Waste Management Authority (LAWMA) for final collection, and disposal of their medical waste at government approved sites.