Iranian Journal of Environmental Health Science and Engineering
Volume:2 Issue: 1, Winter 2005

Structural properties of activated sludge flocs were found to be sensitive to small changes in ionic strength. This study investigates the effect of ionic strength on settling of activated sludge. Samples were taken from activated sludge process of Ghazvin Sasan soft drink wastewater treatment plant, then treated with different ionic strengths of KCl and CaCl2 solution, after that the turbidity of supernatant was measured. The results indicated that low ionic strength resulted in a steeper slope of the accumulated turbidity data for both KCl and CaCl2 as a result of a release of floc fragments and free cells into the supernatant, which did not precipitate during the incubation period. By increasing the ionic strength, the sedimentation improved because of less fragmentation of the sludge flocs. Also at low ionic strengths, the dissociation coefficient was high as a result of a substantial fragmentation of the sludge flocs. The dissociation of the flocs decreased as the ionic strength increased, resulting in a minimum of floc degradation in ionic strength between 0.006 and 0.06M.

Biosurfactants or surface-active compounds are produced by microoaganisms. These molecules reduce surface tension both aqueous solutions and hydrocarbon mixtures. In this study, isolation and identification of biosurfactant producing bacteria were assessed. The potential application of these bacteria in petroleum industry was investigated. Samples (crude oil) were collected from oil wells and 45 strains were isolated. To confirm the ability of isolates in biosurfactant production, haemolysis test, emulsification test and measurement of surface tension were conducted. We also evaluated the effect of different pH, salinity concentrations, and temperatures on biosurfactant production. Among importance features of the isolated strains, one of the strains (NO.4: Bacillus.sp) showed high salt tolerance and their successful production of biosurfactant in a vast pH and temperature domain and reduced surface tension to value below 40 mN/m. This strain is potential candidate for microbial enhanced oil recovery. The strain4 biosurfactant component was mainly glycolipid in nature.

Exposure to inorganic arsenic mainly occurs via drinking water, however because of potential changing of water sources during time, there is not consensus over the best route for assessment of past exposures to arsenic. At present study, we compared three potential sources of data in this regard. Thirty nine human hair samples were taken from persons residing in three villages of Bijar city in Kurdistan province of Iran with different drinking water sources and different levels of arsenic. All the subjects were female and at least one gram of scalp hair was gathered from the distal part of participants’ hair. Samples were analyzed using Neutron Activation Analysis method. Arsenic concentration of water samples were measured using Silver Diethyl Ditiocarbomate Method (SDDC) and the total intake of arsenic through drinking water were calculated for each participant. According to results, arsenic content of drinking water ranged from 0 to 0.455 mg/l (average: 0.18). The figures for arsenic concentration in hair were from 0.012 to 3.41 mg/kg (average: of 0.53) and for calculated total intake from 0 to 8.9g (average: 2.02). A close relationship between calculated total intake via drinking water and arsenic concentration in hair (R=0.711, P<0.001) was obtained and also relationship between current arsenic content of drinking water and arsenic concentration in hair (R= 0.662, p<0.001). Using age as a covaiate did not alter the results.

Basic principles of Integrated Solid Waste Management (ISWM) are: Reduction, Reuse, Recycling and Recovery (4Rs). Composting as an element of ISWM strategy that can be applied to separately collected or mixed wastes, is a controlled aerobic process carried out by successive microbial populations combining both mesophilic and thermophilic activities and leading to the production of carbon dioxide, water, minerals and stabilized organic matter. In this research, comparing between windrow and pit co-composting methods was studied in the city of Damghan, Iran. Waste proportioning was done based on C/N ratio (about 25:1) and moisture content (about 55%). Mixed wastes were located in windrow and pit with natural aeration tunnel. Sufficient oxygen supply was provided in the piles of compostable materials in two systems through frequent turning of the piles in 7 d intervals during the first month. Temperature reached to maximum level in 10-15 d and then depleted (days: 20-25). It reached to the safety level (about 60˚C) based on U.S.EPA and WHO recommendations. Finally, compost was produced with pH=7.7, dark brown color and 30- 35% moisture content. N, P, K, organic matter and organic carbon were measured by standard methods. Results were compared with WHO and U.S.EPA recommendations showing suitable conditions Also it was indicated that pit method was better for maintaining temperature, nitrogen, organic C and organic matter.

Vermicomposting of organic waste has an important part to play in an integrated waste management strategy. In this study, the possibility of heavy metals accumulation with two groups of Iranian and Australian earthworms in sewage sludge vermicompost was investigated. Eisenia fetida was the species of earthworms used in the vermicomposting process. The bioaccumulation of Cr, Cd, Pb, Cu, and Zn as heavy metals by Iranian and Australian earthworms was studied. The results indicated that heavy metals concentration decreased with increasing vermicomposting time. Comparison of the two groups of earthworms showed that the Iranian earthworms consumed higher quantities of micronutrients such as Cu and Zn comparing with the Australian earthworms, while the bioaccumulation of non-essential elements such as Cr, Cd, and Pb by the Australian group was higher. The significant decrease in heavy metal concentrations in the final vermicompost indicated the capability of both Iranian and Australian E.fetida species in accumulating heavy metals in their body tissues.

A study on the removal of cadmium ions from aqueous solutions by pine cone was conducted in batch conditions. Kinetic data and equilibrium removal isotherms were obtained. The influence of different experimental parameters such as contact time, initial concentration of cadmium, pine cone mass and particle size, and temperature on the kinetics of cadmium removal was studied. Results showed that the main parameters that played an important role in removal phenomenon were initial cadmium concentration, particle size and pine cone mass. The necessary time to reach equilibrium was between 4 and 7 hours based on the initial concentration of cadmium. The capacity of cadmium adsorption at equilibrium increased with the decrease of pine cone particle size. The capacity of cadmium adsorption at equilibrium by pine cone increased with the quantity of pine cone introduced (1–4 g/L). Temperature in the range of 20-30°C showed a restricted effect on the removal kinetics (13.56 mg/g at 20°C and a low capacity of adsorption about 11.48 mg/g at 30°C). The process followed pseudo second-order kinetics. The cadmium uptake of pine cone was quantitatively evaluated using adsorption isotherms. Results indicated that the Langmuir model gave a better fit to the experimental data in comparison with the Freundlich equation.

As a result of the regulations on DBPs, interest in NOM removal is increasing and many water treatment plants in developed countries have started to measure the concentration of TOC in their finished waters. Promulgation of the rules will substantially increase these efforts in other countries too. Since the cost of TOC (and DBPs) determination was high, it was decided to study the traditional analysis of COD as a surrogate measure to detect the organic constituents in raw water and the extent to which optimized coagulation with ferric chloride can increase COD removal. The two water samples studied belonged to Karaj and Jajrood Rivers. For both samples the observed values of COD removal by coagulation at lower pH (about 1-1.5 pH values less than the regular pH) were about 85-95 percent without making water turbidity unacceptable. In order to determine the effects of organic content on coagulation, synthetic samples were also prepared with much higher COD values. Again, considerable increases in COD removal have been observed for most of these samples only by decreasing 0.5-2 pH value. The results indicated that a modified coagulation process without need to much increasing the amount of coagulant can be developed for these water samples.

In 1999 the American conference of governmental industrial hygienists (ACGIH) proposed a threshold limit value (TLV) of 0.5 mg/m3 for flour dust with a sensitization notation. As part of this study, a relationship between flour dust concentrations and respiratory symptoms were examined. All 24 male flour subjects and 10 male controls were studied using air samples, ventilatory function testing, and questionnaire on respiratory symptoms. On average, breathing zone respirable and total flour dust in the flour mill were 4.97 mg/m3 and 12.11 mg/m3, respectively. The prevalence of cough, phlgm, difficulty to breathe, and respiratory symptoms were higher in subject group, also during an 8-h shift ventilatory function tests, it was demonstrated that respiratory capacities (FVC, FEV1, PEF) in the flour workers decreased, however, there was no significant statistical difference between case and control groups. Our results suggest that all of different job activities in flour mill may have a great impact on the development of work- related symptoms. Therefore, to minimize the risk of sensitization of occupational exposure during the work process, along with a decrease in mean 8-h TLV average exposure should be achieved.

Anaerobic digestion is among the oldest processes used for stabilization of solid and biosolids. In this survey 12 samples were taken from the digested anaerobic sludge of Isfahan and ShahinShahr WWTP and total solids, volatile solids, total coliform, fecal coliform, Salmonella and viable parasite ova tests were done. Results were compared with the 503 sections of the 40 CFR regulation of the US EPA .The result showed that the average reduction rate was 30% for volatile solids, 4.5×107 MPN/g. dry solids (DS) for total coliform, 5.6×106MPN/g.DS for fecal coliform, 24MPN/4g.DS for Salmonella, and 27 number/4g.DS for viable parasite ova of digested anaerobic sludge in Isfahan. In Shahinshahr WWTP, the average of reduction was 39% in volatile solids, 2.13× 107MPN /g.DS in total coliform, 1.16×106 MPN /g.DS in fecal coliform ,11 MPN/4g.DS in Salmonella and 16 number/4g.DS for viable parasite ova of digested anaerobic sludge . Therefore the digested sludge in Isfahan did not meet the requirements of pathogen reduction in class A and B as well as the reduction requirements for vector attraction, while the digested sludge in ShahinShahr met the requirements of pathogen reduction in class B and vector attraction. So, agricultural use of digested sludge should be made by limiting the kind of crops as well as controlling the harvesting time. The results from the two anaerobic digesters of Isfahan and Shahin Shahr showed that there was a significance correlation between the reduction of volatile solids with total coliform, fecal coliform and Salmonella (P<0.05 , r>0.9 ), while there was no significance correlation between the reduction of volatile solids and viable parasite ova.

Human and his performance is a vital factor in protection of asset including environmental properties. The objective of this study was to evaluate the impact of total system design factors (TSD) on human performance in a power plant. The TSD factors are defined as design factors, which have impact on overall performance of the power plants in context of total human engineering or macroergonomics. The systems being studied are the control rooms and maintenance departments of a 2000 MW thermal power plant. To achieve the above objective, the TSD factors were addressed and assessed through a detailed questionnaire. The relationships between TSD factors and human performance were then examined through non-parametric correlation analysis (Kramer’s Phi) and Kruskal-Wallis test of means. The results of this study show that the macroergonomic factors such as organizational and safety procedures, teamwork, self-organization, job design and information exchange, influence human performance in the power plant. The findings also suggest that the selected macroergonomic factors are correlated to human performance and must be considered, designed and tested concurrently with the engineering factors at the design phase of the system developmental cycle. Consequently, total system’s faults and organizational errors are reduced to an acceptable level and human performance is significantly increased. The main goal in such program is customer''s satisfaction (Internal customers). However, more elaboration on the scientific tools for implementation of TDS factors in context of human performance is also under investigation.