Authors:Faezeh D. Manshadi; Martin Karpiscak Charles P. Gerba Abstract: The goals of this study were to quantify enteric bacterial contamination and survival on several different types of produce during irrigation with wastewater from a dairy operation. Dairy wastewater was used to irrigate three different types of vegetable crops: lettuce, carrot, and bell pepper. This study was conducted over two consecutive growing seasons. Irrigation water and vegetable samples were examined for Escherichia coli and Clostridium perfringens. In the dairy wastewater, E. coli and C. perfringens concentrations averaged 8.2 × 107MPN/100 mL and 5.0 × 104CFU per 100 mL, respectively. Analysis of variance test results indicated that E. coli and C. perfringens concentrations detected on the three crops after irrigation were statistically different (p < 0.0001). The greatest contamination occurred on the carrots followed by lettuce and bell peppers. E. coli and C. perfringens were recovered from the carrots, bell peppers, and soil 49 days after wastewater irrigation of the plots had ceased. Moisture content of the soil was statistically significantly related to survival of the organisms in the soil. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.161
Authors:R. B. Almada; G. A. T. Fontoura, D. M. Bila, G. L. Sant'Anna M. Dezotti Abstract: The industrial wastewater from a carbon monoxide production unit was treated by physico-chemical processes in order to achieve a quality level appropriate for reuse. In preliminary tests, coagulation/flocculation (CF), sand filtration and activated carbon adsorption were investigated in order to select the materials and the process conditions. Based on the results a combined treatment was proposed: CF followed by down-flow filtration in a combined medium (sand and granular activated carbon). The results obtained in a bench-scale treatment unit showed that the combined treatment removed wastewater turbidity (95%), total suspended solids (97%), volatile suspended solids (81%), chemical oxygen demand (74%) and dissolved organic carbon (65%). Polycyclic aromatic hydrocarbons (PAHs) were removed to non-detectable levels. The residual conductivity of the treated wastewater is a matter of concern, and considering the water characteristics of this industrial process, a reuse scheme was proposed based on on-line monitoring and control of conductivity and partial reuse of the treated wastewater. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.081
Authors:Lauren Weinrich; Charles N. Haas Mark W. LeChevallier Abstract: A review of recent literature focuses on the fouling phenomena in membrane systems for desalination, quantification and qualification of parameters related to biological fouling (biofouling), and emerging areas for prevention. In particular, biofouling of seawater reverse osmosis (SWRO) is widely regarded as the most important area for future research on this topic. Reducing membrane fouling is fundamental to seawater treatment but is not well managed. The current state of industry knowledge is evaluated with particular focus on SWRO membrane biofouling, as well as its measurement and mitigation. Specific shortcomings and possible solutions are reviewed regarding the role of assimilable organic carbon, chemical treatment and other components in understanding the fouling process, impacts from pretreatment, level of assimilable nutrients, modeling applications, and real time monitoring. A critical review of recent advances in understanding organic and biological fouling is presented because these are the most difficult to control and least understood. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.056
Authors:Oluwajinmi Daniel Aina; Farrukh Ahmad Abstract: Trihalomethane (THM) occurrence in reclaimed water and its exposure risk to human health during non-potable reuse was evaluated for a coastal Arabian city. Recycled water was monitored at two representative wastewater treatment facilities: a city-wide activated sludge treatment (AST) plant and a neighborhood membrane bioreactor (MBR). Actual total THM concentrations in the post-chlorinated effluents varied with effluent temperature, peaking at 69.28 ± 2.54 μg/L and 41.15 ± 2.34 μg/L in AST and MBR effluents, respectively, in summer. Higher bromide concentration and favorable Br−/Cl2 ratio during disinfection in the AST resulted in stronger brominated THM speciation. Conversely, the MBR effluent was dominated by chloroform. Salinity fingerprinting indicated the presence of saline water in the AST effluent. Individual excess lifetime cancer risk (IELCR) was calculated using the outdoor box exposure model based on annual peak THM concentrations and peak THM formation potential (THMFP) for each species. Inhalation exposure to chloroform in the MBR effluent using peak THMFP values presented the highest cancer risks of 1.28 × 10−6 and 1.12 × 10−6 to residential adult and child receptors, respectively, exceeding the USEPA IELCR guidance threshold of 1 × 10−6 for carcinogens. Chlorinated THM species are important in determining the health risk from reclaimed water during non-potable water reuse. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.062
Authors:K. Kabbaj; M. Mahi A. Saoiabi Abstract: The Drarga treatment plant was chosen as a pilot site for treatment and reuse of domestic wastewater. It uses reed beds as a tertiary treatment, so this research was conducted to study the performance of the reeds over a period of 3 years (March 2006–March 2009), that is three growing seasons. The reeds were cut after 2 years. Knowing that the Drarga climate is semi arid, we studied the behaviour of purification by reeds over seasonal changes. The reeds were effective in removing pollution over the three growing seasons studied; the average removal of BOD5 over 3 years was 71%. The maximum removal efficiency was in winter; this is associated with high oxygenation of the water mass caused by mixing and stirring induced by the movement of the long stems of the reeds. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.068
Authors:Biplob Kumar Pramanik; Dipok Chandra Sarker Abstract: The Buriganga River receives partially treated sewage effluent, sewage polluted surface runoff and untreated industrial effluent from Dhaka city. This study examines the present status of surface water quality of Buriganga River at different locations in Dhaka City. The values of dissolved oxygen (DO), pH, colour, total coliforms, turbidity and ammonia were always very high over the year 2011. The maximum level of DO concentration was 3.4 mg/l, which is below the acceptable limit for surface water. Results also showed that high turbidity and low colour values were found in the rainy season while low turbidity and high colour values were found in the dry season. Moreover, the values of all parameters were always high at Buri 2 (Hazaribagh) because of the proximity of industrial sites. It is important to improve the water quality of the Buriganga River by protecting it from pollution. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.059
Authors:S. F. Barker; R. Faggian, J. Blackbeard, G. Hepworth A. J. Hamilton Abstract: In 2008, vegetable growers observed stunted lettuce plants showing signs of chlorosis and wilting. It was suspected that monochloramine in the recycled water used for irrigation, in combination with extreme environmental conditions (high irrigation water salinity and extreme heat), was responsible for these crop failures. A series of glasshouse studies was conducted to evaluate the impact of monochloramine concentration alone on iceberg lettuce seedlings, as well as in combination with high salinity and hot ambient temperatures. Monochloramine concentrations up to 9 and 15 mg L−1 Cl2 for continuous and initial irrigation only, respectively, did not affect the weight of iceberg lettuce heads (p > 0.05), while the combination of monochloramine (4–5 mg L−1 Cl2) and salinity (3,500 μS cm−1) did not significantly affect harvest measurements (p > 0.05). We therefore conclude that it is unlikely that monochloramine was responsible for the observed crop failures. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.019
Authors:A. R. Keegan; B. Robinson, P. Monis, M. Biebrick C. Liston Abstract: Validation studies were undertaken at Adelaide metropolitan wastewater treatment plants to establish the actual log10 reduction values (LRVs) of pathogens (viruses and Cryptosporidium) across activated sludge plants (ASPs) as an alternative to accepting the default values attributed by the Department of Health and Ageing (DHA). Grab samples were collected across a 6-week period and assessed for pathogens (adenovirus and Cryptosporidium) and indicator microorganisms (sulphite-reducing clostridia and F-RNA bacteriophage). Through applying the validation process, the DHA has revised the default value for reduction of viruses with an increase from 0.5 log10 to 1 log10 while the value for protozoa remains at 0.5 log10 based on the combined data for a well-operated and maintained ASP. This provides the basis for considering further work at individual plants which may allow higher log credits to be obtained on a plant by plant basis. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.032
Authors:Muhammad Ashraf; Muhammad Imtiaz, Muhammad Abid, Muhammad Afzal Sher Muhammad Shahzad Abstract: When untreated wastewater is used for the irrigation of crops, dissolved heavy metals may impose negative impacts on plant growth and pose health risks. However, silicon nutrition may improve plant tolerance to metal toxicity through external and internal plant mechanisms. This work aims at investigating the effects of silicon on copper, nickel, manganese, cadmium and zinc detoxification in tomato plants. The plants were grown for 50 days by irrigating with tap water and wastewater and having silicon added at 25, 50 and 75 mg kg–1 soil. Results revealed that wastewater irrigation caused an increase of 277–480% in copper, 178–233% nickel, 355–680% manganese, 500–900% cadmium and 117–337% zinc in tomato plants compared to tap water irrigation. The root:stem metal ratios showed that a major portion of absorbed metals was translocated to aerial plant parts when wastewater was applied without silicon. However, silicon supplementation precipitated the metals in soil and influenced their uptake and partitioning within the plant body. The shoot dry matter of tomato plants was negatively correlated with wastewater-induced stem metal concentrations. This study suggests that silicon-assisted metal tolerance of tomato plants was attributed to metal precipitation in soil, complexation in roots and, hence, reduction in their translocation to stems and leaves. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.066
Authors:Papita Das Saha; Jaya Srivastava Shamik Chowdhury Abstract: The efficacy of seashells as a new adsorbent for removal of phenol from aqueous solutions was studied by performing batch equilibrium tests under different operating parameters such as solution pH, adsorbent dose, initial phenol concentration, and temperature. The phenol removal efficiency remained unaffected when the initial pH of the phenol solution was in the range of 3–8. The amount of phenol adsorbed increased with increasing initial phenol concentration while it decreased with increasing temperature. The adsorption equilibrium data showed excellent fit to the Langmuir isotherm model with maximum monolayer adsorption capacity of 175.27 mg g−1 at pH 4.0, initial phenol concentration = 50 mg L−1, adsorbent dose = 2 g and temperature = 293 K. Analysis of kinetic data showed that the adsorption process followed pseudo-second-order kinetics. Activation energy of the adsorption process, calculated using the Arrhenius equation, was found to be 51.38 kJ mol−1, suggesting that adsorption of phenol onto seashells involved chemical ion-exchange. The numerical value of the thermodynamic parameters (ΔG
0, ΔH
0 and ΔS
0) indicated that adsorption of phenol onto seashells was feasible, spontaneous and endothermic under the examined conditions. The study shows that seashells can be used as an economic adsorbent for removal of phenol from aqueous solution. PubDate: 2013-05-16T19:00+00:00 DOI: 10.2166/wrd.2013.070
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