- Comparison of ultraviolet light emitting diodes with traditional UV for
- Authors: M. J. Crook; B. Jefferson, O. Autin, J. MacAdam A. Nocker
Abstract: The current technological status of ultraviolet light emitting diodes (UV-LEDs) has reached a point where small-scale ultraviolet (UV) water disinfection applications, that is, for greywater reuse appear increasingly promising. This study compares the germicidal and economical aspects of UV-LEDs with traditional UV. Pure cultures and environmental greywater samples were exposed to different radiation doses from both UV sources with the germicidal effect comparative at equivalent doses. The impact of particle size on disinfection efficiency was investigated in two greywater fractions of varying mean particle size. Disinfection efficiency was found to be dependent on particle size with larger particles reducing microbial inactivation for both UV sources. Post-UV blending to detach particle-associated coliforms resulted in higher bacterial counts for both UV sources although to a lesser extent for UV-LEDs suggesting that it might be less affected by the presence of particles than traditional UV sources, possibly due to the UV radiation being emitted by multiple diodes at different angles compared to the traditional UV collimated beam setup. Nevertheless, removal of particles prior to UV disinfection is necessary to meet strict water reuse standards. Although UV-LEDs are currently prohibitively expensive, improvements in performance indicators might make this technology economically competitive within the next few years.
- Options and limitations of hydrogen peroxide addition to enhance radical
formation during ozonation of secondary effluents
- Authors: U. Hübner; I. Zucker M. Jekel
Abstract: The oxidation of secondary effluent with ozone and O3/H2O2 (peroxone) was evaluated in batch experiments as pre-treatment for soil aquifer treatment for non-potable reuse purposes. The addition of hydrogen peroxide improved the reduction of ozone-resistant compounds with an optimized radical formation at 0.5 mol H2O2/mol O3. However, the improvement of radical formation was shown to be limited to approximately 30–40% independent from ozone dosage. Also a preozonation step did not accelerate efficiency of subsequent peroxone treatment. Thus, other treatment options, such as an increase of ozone dosages, need to be considered for more efficient removal of ozone-resistant compounds. However, the peroxone process might still be a promising option for oxidation of bromide containing effluents, since a reduction of bromate formation can allow the application of higher ozone dosages.
- Contemporary design, operation, and monitoring of potable reuse systems
- Authors: J. E. Drewes; S. J. Khan
Abstract: Water scarcity driven by population growth, lack of conventional supplies, and climate change impacts have resulted in increasing interest worldwide in drinking water augmentation using treated wastewater effluents. Potable reuse can occur indirect or direct, but is also practiced in many places as ‘de facto reuse’, where upstream wastewater discharge occurs to drinking water supplies. With this increasing recognition of potable reuse, there is very limited guidance and standardization for proper design and operation of potable reuse schemes that is protective of public health. This study provided guidance on contemporary approaches for the design, operation, and monitoring of potable reuse schemes, including source water characterization and source control approaches; linking water quality treatment performance goals to health risks; risk mitigation strategies including the design principles of multiple barriers for microbial and chemical contaminants; assessing system reliability and fail-safe design approaches; and, finally, monitoring strategies for process performance and compliance.
- Desulfurization performance of biotrickling filter on the removal of flue
gas adsorbent produced by dual-alkali flue gas desulfurization process
- Authors: Tianlong Zheng; Li Wang, Jianhua Wang, Niantao Xue Qunhui Wang
Abstract: A biotrickling filter (BTF) was used to investigate the elimination of flue gas adsorbent containing sulfite, sulfate, and hydrosulfate; it was undertaken to replace the regeneration step of dual-alkali flue gas desulfurization. Sulfate-reducing bacteria (SRB) isolated from landfill leachate were inoculated, and overall desulfurization performance as well as impact resistance was evaluated. The results showed that an efficient SRB could reduce the start-up time to 1 h, which is one third of that required for initial condition, for a sulfite removal efficiency above 80%. Further, the sulfite removal efficiency rose to 98% in 3.9 h with the lower packing load of 5.56 kg SO3
2−-S/(m3d), and in 6.4 h for 6.37 kg SO3
2−-S/(m3d). In contrast, 85% removal efficiency in 5 h for sulfate and 98% removal efficiency in 0.5 h for hydrosulfite were obtained when the packing loads were 0.95 kg SO4
2−-S/(m3d) and 1.76 kg HSO3
−-S/(m3 d), respectively. Moreover, the BTF could quickly restore after impact shock, such as, 0.5 h restoration time for initial pH which varied from 4.5 to 6.5, 6 d for 27 d shutdown behavior, and 4 d for 5 h high temperature shock of 85 °C. Therefore, the BTF system was an effective method for flue gas adsorbent treatment.
- Treatment of domestic greywater by geotextile filter and intermittent sand
- Authors: Sebastian Ignacio Charchalac Ochoa; Ken Ushijima, Nowaki Hijikata Naoyuki Funamizu
Abstract: Intermittent sand filtration (ISF) is an efficient system for treatment of greywater; however, the high quality of effluent and the simple set-up contrast with the high failure rate due to clogging of surface layers. The efficacy of several polypropylene non-woven geotextiles (apparent opening size from 0.10 to 0.18 mm) used as primary treatment filters to remove suspended particles from domestic greywater and the effects of this pretreatment in the performance of fine and small media size (0.3 and 0.6 mm) ISFs was examined. Results showed geotextile achieved suspended solids (SS) removal rates from 25 to 85% and chemical oxygen demand (COD) from 3 to 30%; although the portion larger than 75 μm was removed at higher rates (55–90%), particles smaller than the nominal pore size of the filter were also captured. Geotextile used as pretreatment resulted in improvement of lifetime of the ISFs over an experimental run of 60 days. The vertical profile of volatile organic matter in the ISFs was evaluated at the end of the experiment and it showed a clear reduction in the accumulation of organic material on the top layer of the ISFs, effectively avoiding its early failure by accumulation of solids.
- Adsorption of polycyclic aromatic hydrocarbons from wastewater by using
silica-based organic–inorganic nanohybrid material
- Authors: Ali Balati; Afsaneh Shahbazi, Mostafa M. Amini Seyed Hossein Hashemi
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are a group of priority pollutants, which are classified as persistent hazardous contaminants. Herein, the adsorption of three PAHs, naphthalene (NAP), acenaphthylene (ACN), and phenanthrene (PHN), from wastewater onto NH2-SBA-15 organic–inorganic nanohybrid material as a function of pH of the media (2–10), sorbent dosage (0.5–3.5 g L−1), PAH concentration (1–18 mg g−1), and temperature (25–45 °C) were elucidated. The prepared adsorbents were characterized by scanning electron microscope, transmission electron microscopy, X-ray diffractions, and thermogravimetric analysis. Among Langmuir, Freundlich, and Temkin isotherms models, it was found that the Langmuir model gave an excellent overall fit (R
2 > 0.97). The maximum adsorption capacity of 1.92, 1.41, and 0.76 mg g−1 was obtained for NAP, ACN, and PHN, respectively. Adsorption kinetics of PAHs onto NH2-SBA-15 was in accordance with the pseudo-second-order model, providing evidence that pore mass transferring was involved. PAHs' adsorption was strongly dependent on temperature, and confirmed the spontaneous and endothermic nature of the process. The optimized sorption condition was successfully applied to the real petroleum refinery wastewater samples and the adsorption capacity of NH2-SBA-15 was satisfactory for PAHs' studies as 1.67, 1.06, and 0.24 mg g−1 for NAP, ACN and PHN, respectively. Furthermore, reusability was successfully tested by five sequential recoveries.
- Validation of the Goreangab Reclamation Plant in Windhoek, Namibia against
the 2008 Australian Guidelines for Water Recycling
- Authors: Ian B. Law; Jurgen Menge David Cunliffe
Abstract: Australia has had Guidelines in place for water recycling (for all uses other than the augmentation of drinking water supplies) since 2006. These Guidelines were extended to cover potable reuse in May 2008 and have been applied to two potable reuse projects in Australia – one a trial plant in Perth, Western Australia and the second for a large AUD$2.6 × 109 scheme in Brisbane, Queensland. All reclamation plants in Australia must be ‘validated’ against the Australian Guidelines for Water Recycling prior to being put into operation. The majority of advanced reuse schemes incorporate the dual membrane process – microfiltration or ultrafiltration followed by reverse osmosis (RO) – in the treatment trains and while this membrane based treatment has been shown to produce a very high quality of product water, it does come at a cost and there is renewed interest in alternative treatment technologies that offer cost savings and are more sustainable. This paper uses data gathered in Australia from a range of advanced reclamation plants, as well as design and actual performance criteria from the Goreangab Plant, to ‘validate’ the latter and, given the longevity of the Windhoek direct potable reuse experience, lend support to more serious consideration of non-RO based plants for potable reuse applications.
- The relationship between chlorine consumption and trihalomethane formation
from hydrophobic and transphilic fractions: a comparative study between
two dams of east Algeria
- Authors: Dhaouadi Mellahi; Ridha Zerdoumi, Nacer Rebbani Abdelhak Gheid
Abstract: In Algeria, the use of chlorine in drinking water treatment is a widespread practice. When chlorine combines with natural organic matter (NOM), it forms various chlorine by-products such as trihalomethanes (THMs). In this work, we studied the relationship between chlorine consumption and THM formation, by chlorination of hydrophobic and transphilic (TRS) fractions. We compared the kinetic behavior and the THM formation potential of two major dams in east Algeria. A nonlinear regression modeling study showed a good correlation of the specific chlorine consumption and the specific THM formation. In the case of Ain Zeda dam and at pH = 7, the specific THM yield coefficients α
S were: 6.57 and 10.22 μg-THM/mg-Cl2.mg-C.L−1 for hydrophobic and TRS fractions, respectively, while at the same pH, they were 12.07 and 23.66 μg-THM/mg-Cl2.mg-C.L−1 for Ain Dalia dam. Although the NOM concentration of Ain Zeda dam was higher than that of Ain Dalia dam, the THM formation potential of Ain Dalia dam was greater than that of Ain Zeda dam. It seems clear that the water source origin and characteristics play a key role in this case. They affect the THM formation due to the complex composition of humic substances which differs from one source to another.