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1

Anaerobic treatment of industrial wastewater by UASB reactor integrated with chemical oxidation processes; an overview

100%

Yasar A. , Tabinda A. B.

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nr 5

EN

In order to upgrade the quality of anaerobically treated effluent to a level recommended for irrigation, integration of a UASB reactor with UV and AOPs (advanced oxidation processes) (Ozone, H2O2/UV, Fenton, and photo-Fenton) could be a better option for almost complete colour, COD removal, and disinfection of pathogens. High efficiency of the UASB can be maintained by proper process conditions, including temperature, sludge age, pH, hydraulic retention time, and gas-liquid-solid separator (GLSS) design. A fraction of the COD and colour is usually non-biodegradable and renders difficulty for anaerobic digestion. AOPs degrade the organic molecules and converting completely the organic compounds to non-toxic components such as CO2 and/or water. As far as disinfection is concerned, advanced oxidation processes are proved to be extremely effective in killing pathogens (total coliform, fecal coliform, fecal streptococci, salmonella, and E. coli) due to their strong oxidative characters. Although AOPs effectively accomplish pathogen elimination, re-growth of pathogenic microorganisms can take place in the treated effluent. Re-growth potential of pathogens provides helpful information about the quality of the treated water, which is very important in all possible reuse options. The combined application of AOPs with anaerobic treatment minimizes the chances of regrowth due to irreparable damage to nucleic acid. This review paper focuses primarily on the process conditions and treatment efficiency for UASB treatment systems, and to evaluate the advanced oxidation processes (AOPs) as an option for post treatment.

2

Heavy metal uptake and toxicity in tissues of commercially important freshwater fish (Labeo rohita and Wallago attu) from the Indus river, Pakistan

80%

Iqbal A. , Tabinda A. B. , Yasar A. , Mahfooz Y.

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tom 26

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nr 2

EN

The purpose of this study was to evaluate the accumulation of heavy metals in the liver, skin, gills, and muscles of two freshwater edible fish species (Labeo rohita and Wallago attu) collected from Taunsa barrage of the Indus River in Pakistan. Fish samples were collected on a seasonal basis and were analyzed by atomic absorption spectroscopy. Gills and liver accumulated relatively higher heavy metal concentrations. All fish organs accumulated the highest metal content in winter and the lowest in summer. Heavy metals accumulated in the order Fe>Zn>Ni>Cu>Pb>Cr>As in the body of Labeo rohita and the tissues with the abundance were liver>gills>skin>muscles. Similarly, the sequence of heavy metal accumulation in Wallago attu was Fe>Zn>Cu>Ni>Cr>Pb>As, and the targeted tissues were gills>liver>skin>muscles. Heavy metal bioaccumulation was different in both species. Fe was the highest and As was the least accumulated heavy metal in both of these fish species. The tissues of Wallago attu accumulated higher concentrations of Ni (83%), Cu (64%), Cr (50%), Fe (2.95%), and Zn (26%) compared to tissues of Labeo rohita. However, Pb (67%) and As (22%) accumulation in tissues of Labeo rohita were higher compared to their concentrations in tissues of Wallago attu. Overall metal burden was 10% higher in Wallago attu compared to Labeo rohita. Heavy metal concentration in fish tissues were compared with FAO threshold values.

3

Advanced oxidative decolorization of Red Cl-5B: effects of dye concentration, process optimization and reaction kinetics

80%

Khan H. , Ahmad N. , Yasar A. , Shahid R.

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nr 1

83-92

EN

Process conditions (dye concentration, pH and oxidant dose) were optimized for UV, O₃, H₂O₂/UV, O₃/UV, H₂O₂/O₃, and H₂O₂/O₃/UV to treat Red Cl-5B dye of varying concentrations (100, 300, and 500 mg/L). Ozonation resulted in color removal of more than 90%, whereas H₂O₂/O3 showed no advantage over the O₃ alone. However, H₂O₂/UV was found to be very suitable as it gave almost 100% decolorization in a relatively short reaction time. Decolorization rate for all processes was reduced to half when the dye concentration was increased from 100 to 300 mg/l. Comparative study of rate constants revealed that H₂O₂/UV is four times faster than that of UV alone. On the other hand O₃/H₂O₂ is three to four times slower than O₃ alone.

4

A comparison of engine emissions from heavy, medium, and light vehicles for CNG, diesel, and gasoline fuels

71%

Yasar A. , Haider R. , Tabinda A. B. , Kausar F. , Khan M.

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nr 4

EN

Like other developing countries (Brazil, Argentina, and India) compressed natural gas (CNG) is becoming a popular vehicular fuel in Pakistan. Rapid shifting of diesel and gasoline vehicles to CNG has brought Pakistan the highest number of CNG vehicles in the world. To quantify a possible decrease in vehicular emissions for different types of vehicles, engine and fuel types were monitored for five parameters: SO2, CO, NO, hydrocarbons, and smoke opacity. Emissions from heavy vehicle engines shifting from diesel to CNG showed a decrease in HC (14 times), NO (2.8 times), and smoke opacity (3.2 times), while shifting diesel car engines to CNG resulted in reduced emissions of HC (24.6 times), NO (2.8 times), and smoke opacity (6 times). However, switching of light vehicles such as gasoline car engines to CNG released low emissions of HC (4.6 times), smoke opacity (1.2 times), SO2 (1.2 times), and CO (1.1 times), but an increase in NO (1.2 times) was observed. Similarly, a 4-stroke CNG rickshaw engine increased NO emissions by 1.4 times over a 4-stroke gasoline rickshaw engine.