Imran Hashmi

Cancer and non-cancer risk assessment of trihalomethanes in urban drinking water supplies of Pakistan.

This study aims at monitoring and risk assessment of trihalomethanes (THMs) such as chloroform, bromodichloromethane, dibromochloromethane and bromoform, in the drinking water supplies of Rawalpindi and Islamabad. THMs were monitored at twenty locations in these twin cities using solid phase micro extraction-gas chromatography (SPME-GC). Total concentration of THMs was ranged between 21 and 373μg/L, whereas both cities had an average total THMs concentration of 142 and 260μg/L, respectively. Chloroform was found as one the major contributor to the THMs concentration (>85%). The occurrence of THMs followed the given order: chloroform, bromodichloromethane>dibromochloromethane>bromoform. Lifetime cancer risk assessment of THMs was carried out using prediction models via different exposure routes (ingestion, inhalation and dermal). An average lifetime cancer risk was found to be 0.74×10(-4) and 1.24×10(-4) for Rawalpindi and Islamabad, respectively. The number of expected cancer cases per year could reach two cases for each city. Hazard index values were found below unity for both the cities implying that there would be no considerable non-cancer risk. Oral ingestion was found to be one of the main routes of exposure for both types of risk which was followed by inhalation and dermal routes.

Synthesis of silver-doped titanium TiO 2 powder-coated surfaces and its ability to inactivate pseudomonas aeruginosa and bacillus subtilis

Hard, nonporous environmental surfaces in daily life are now receiving due recognition for their role in reducing the spread of several nosocomial infections. In this work, we established the photokilling effects of 1% silver-doped titanium dioxide TiO2. The nanoparticles synthesized by liquid impregnation method were characterized using X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The Ag-TiO2 nanoparticle coatings that have been applied on glass and venetian blind surfaces were effective in generating a loss of viability of two bacteria (Pseudomonas aeruginosa and Bacillus subtilis) after two hours of illumination under normal light in the visible spectrum. Such surfaces can be applicable to medical and other facilities where the potential for infection should be controlled.

Distribution, toxicity level, and concentration of polycyclic aromatic hydrocarbons (PAHs) in surface soil and groundwater of Rawalpindi, Pakistan

Abstract In this study, the distribution, toxicity level, and relationship of polycyclic aromatic hydrocarbons (PAHs) with total organic content (TOC) have been investigated using surface soil and ground water samples from an area adjacent to petrochemical plant in Pakistan. Six PAHs, naphthalene, acenaphthene, phenanthrene, anthracene, flouranthene, and chrysene, were selected from the 16 Environment Protection Agency priority pollutants list. ΣPAHs range from 2,700 to 4,443 μg/g (average: 3,672 ± 592 μg/g) in soil and 201–1,634 ng/L (average: 763 ± 377 ng/L) in water. The compositional profile of PAHs revealed that low molecular weight 3–4 ring PAHs were predominant. The ratios of phenanthrene/anthracene reflected the pyrogenic origin of PAHs. The relationship of PAHs with TOC has also been investigated and a positive correlation was observed between ΣPAHs and TOC. This indicates that partitioned in organic matter may be the possible source of PAHs in water. An assessment using widely cited guidelines i...

Insights into quorum quenching mechanisms to control membrane biofouling under changing organic loading rates

A quorum quenching (QQ) consortium comprised of both acyl homoserine lactones (AHLs)- and autoinducer-2 (AI-2)-degrading bacteria, either immobilized in polymer-coated alginate beads or in liquid suspension, was examined for fouling control in lab-scale MBRs under both steady and changing organic loading rates (OLRs). Under steady conditions the QQ consortium retarded biofouling by a factor of 3. However, a continuous increase in OLR vastly reduced the effectiveness of QQ bacteria; the biofouling was retarded only by factors of 1.4-1.8. A significant increase in extracellular polymeric substance (EPS), especially loosely-bound EPS in mixed liquor together with an increase in polysaccharide content up to 4 times in EPS resulted from the increase in OLR, was attributed to the impaired QQ efficacy. In control MBRs, cake layer resistance was the major factor (>60%) contributing to the increased trans-membrane pressure, as compared with pore blockage resistance and intrinsic membrane resistance. In contrast, the pore blockage resistance became dominant in QQ MBRs (>40%).

Biotreatment of chlorpyrifos in a bench scale bioreactor using Psychrobacter alimentarius T14

Bacteria tolerant to high pesticide concentration could be used for designing an efficient treatment technology. Bacterial strains T14 was isolated from pesticide-contaminated soil in mineral salt medium (MSM) and identified as Psychrobacter alimentarius T14 using 16S rRNA gene sequence analysis. Bench scale bioreactor was evaluated for biotreatment of high Chlorpyrifos (CP) concentration using P. alimentarius T14. Effect of various parameters on bioreactor performance was examined and optimum removal was observed at optical density (OD600 nm): 0.8; pH: 7.2; CP concentration: 300 mg L−1 and hydraulic retention time: 48 h. At optimum conditions, 70.3/79% of CP/chemical oxygen demand (COD) removal was achieved in batch bioreactors. In addition, P. alimentarius T14 achieved 95/91, 62.3/75, 69.8/64% CP/COD removal efficiency with addition of CS (co-substrates), CS1 (yeast extract + synthetic wastewater), CS2 (glucose + synthetic wastewater) and CS3 (yeast extract), respectively. Addition of CS1 to bioreactor could accelerate CP removal rate up to many cycles with considerable efficiency. However, accumulation of 3, 5, 6-trichloro-2-pyridinol affects reactor performance in cyclic mode. First-order rate constant k1 0.062 h−1 and t1/2 11.1 h demonstrates fast degradation. Change in concentration of total chlorine and nitrogen could be the result of complete mineralization. Photodegradation of CP in commercial product was more than its pure form. Commercial formulation accelerated photodegradation process; however no effect on biodegradation process was observed. After bio-photodegradation, negligible toxicity for seeds of Triticum aestivum was observed. Study suggests an efficient treatment of wastewater containing CP and its metabolites in batch bioreactors could be achieved using P. alimentarius.

Performance evaluation and bacterial characterization of membrane bioreactors.

A bench-scale conventional membrane bioreactor (C-MBR), a moving bed membrane bioreactor (MB-MBR) and an anoxic/oxic membrane bioreactor (A/O-MBR), operating under similar feed, environmental and operating conditions, were each evaluated for their treatment performance and bacterial diversity. MBRs were compared for the removal of organics (COD) and nutrients (N and P) while pure culture techniques were employed for bacterial isolation and an API 20E kit was used to identify the isolates. Pseudomonas aeruginosa, selected as a representative of denitrifying microorganisms, was isolated only from the A/O-MBR using Citrimide Agar. Using PCR, the nitrifying bacteria Nitrosomonas europaea was detected only in the MB-MBR. On the other hand, Nitrobacter winogradskyi was detected in all three reactors. Addition of media and maintenance of a lesser DO resulted in the highest TN removal in the A/O-MBR as compared to the C-MBR and the MB-MBR, whereas better nitrification was observed in the MB-MBR than in the C-MBR.

Microbiological quality of drinking water in urban communities, Rawalpindi, Pakistan

Abstract Bacterial contamination and residual chlorine were investigated over a three month period in four different areas of Rawalpindi city namely Ratta Amral (R1), Satellite town (R2), Westridge (R3), and Tench Road (R4). Treated water from Khanpur and Rawal Lake Filtration Plant is supplied to these communities, which treat surface water with conventional processes (coagulation, flocculation, and sedimentation). Eight sampling sites were chosen from each area to give wide geographic coverage and correspondingly, wide range of water residence times. The drinking water quality in the distribution network was evaluated by measurements on water samples taken from the water source, overhead reservoir and residential taps. Parameters include temperature, pH, turbidity, total dissolved solids (TDS), conductivity, total organic carbon (TOC), disinfectant residuals, coliforms, and Spread plate count (SPC) as per standard methods. Significant losses were observed in both chlorine and chloramine residuals in R1 ...

Comparison of degradation studies in a biosimulator by continuous cultivation of Pseudomonas and indigenous microorganisms with varied dissolved oxygen concentrations

The aim of this study was to compare the potential of a pure bacterial culture of Pseudomonas with the potential of an indigenous microorganism for malathion degradation by continuous cultivation using two different sets of conditions (with-culture: Pseudomonas, and without-culture: indigenous microorganisms) at varied dissolved oxygen (DO) concentrations (4.0 and 8.0 mg/L) in a biosimulator. The samples were analysed for pH, DO and COD (unfiltered). Gas chromatography (GC) revealed that almost 90% of malathion removal was achieved within ten hours of treatment in both studies of with-culture using 4.0 and 8.0 mg/L DO, whereas COD was considerably reduced during the treatment process and the removal efficiency was found to be above 90% in both conditions. The removal of COD was found to be in direct relation to retention time. However, the unfiltered COD and malathion removal efficiency was significantly influenced by DO. The percentage degradation of malathion using 4.0 mg/L DO, with-culture after 10 hours was 90.01%, whereas after 51 hours it was 99.03%. The without-culture studies showed percentage values which were 38.29% after 10 hours, whereas the corresponding value after 51 hours was 96.84%. Similarly, the percentage degradation of malathion using 8.0 mg/L DO, with-culture studies revealed that almost 89.40% malathion degradation was achieved after 10 hours, whereas it was 96.91% after 51 hours after inoculation of the culture. However, for the without-culture studies the value after 10 hours was 52.34%, whereas 96.86% malathion degradation was achieved after 51 hours without added culture. Although no significant variation in the pH was observed during the study the pH values increased gradually during the treatment process in all of the conditions. A critical evaluation of data presented revealed that the degradation potential of Pseudomonas was better when compared to the degradation potential of indigenous microorganisms.

Effect of trihalomethanes (chloroform and bromoform) on human haematological count

With the increasing concerns about the harmful effects of disinfection products, the process of chlorination is becoming questionable. Bromoform and chloroform are among the most frequently occurring disinfection by-products. Haematological parameters are an important indicator of human well-being which is why the prime objective of the current study was to conduct a dose-response assessment to investigate the effects of trihalomethanes on human haematological count. Blood samples of healthy subjects were exposed to different concentrations (10, 30 and 50 μg/mL) of chloroform and bromoform in vitro to analyse how these compounds affected the haematological count with increasing dose concentrations. Headspace gas chromatography analysis was also conducted on samples to assess the difference between measured and spiked values of doses. The results indicated that the damage caused by bromoform was statistically more significant as compared to chloroform. Haemoglobin (HGB) and mean corpuscular haemoglobin concentration levels lowered as they were significantly affected (p < 0.05) by bromoform at all administered doses. It also significantly damaged platelet level at doses of 30 (p < 0.05) and 50 μg/mL (p < 0.01). Conversely, the damage caused by chloroform was statistically less significant (p > 0.05).

Efficacy of UV-C photolysis of bisphenol A on transcriptome alterations of genes in zebrafish embryos

ABSTRACT The purpose of this study was to investigate the efficacy of UV-C direct photolysis of bisphenol A (BPA) as a remediation method of BPA contamination. We used zebrafish embryos as a model organism to test the toxicity and residual biological activity by measuring cytochrome P4501A1 (CYP1A), aromatase B (Aro B) and heat shock proteins (HSP-70) transcript levels. The mRNA levels of CYP1A gene increased about two fold while exposure of zebrafish embryos at 72 hpf resulted in significant induction (P = 0.048) of Aro B at 100 µg/L of BPA. Exposure of zebrafish embryos at 72 hpf to increasing concentrations of BPA resulted in significant induction (P = 0.0031) of HSP-70 transcript level. UV treatment of BPA resulted in a significant reduction in toxicity by reducing mortality of zebrafish embryos. The results suggest that UV-C direct photolysis may be an effective method for remediation of BPA contamination. Further studies will be necessary for better understanding of the identity and relative activity of the UV degradation by-products.