The homogeneous advanced oxidation process of UV/H2O2 was utilized to decolourize CI Reactive Red 195A (RR195A) as one of the most used dyes in the textile industry in Queensland. The UV radiation source was a low-pressure mercury arc lamp (60W emitting at 253.7nm). In this study, the effects of initial hydrogen peroxide (H2O2) dosage, dye concentration, pH and temperature were examined to find out the optimum operating conditions of the treatment process. Complete decolourization was achieved in the relatively short time of 20-30 minutes irradiation. Faster decolourization was achieved at low pH and high temperature. The removal rate increased with increasing initial concentration of H2O2 up to an optimum value. The decolourization reaction was found to follow at least initially first order kinetics with respect to the dye concentration. However, even after near complete removal of the active dye from the solution, approximately 60% of the COD was still remaining, indicating only partial breakdown of the dye molecule. In general, the result indicates that the UV/H2O2 technology proved to have good potential for removing dyestuff from wastewater but further treatment might be necessary to achieve complete mineralization of the organic intermediates.
In this study, the degradation of polychlorinated biphenyls (PCBs), Aroclor 1260, using the UV/H2O2 system was investigated. The effects of initial H2O2 concentration, initial pH of the solution and initial PCB concentration were studied using a batch tubular reactor equipped with a 254 nm low-pressure Hg lamp. PCB concentration was analyzed using GC-ECD as total aroclor.
Results show that there is an optimum H2O2 concentration that maybe used beyond which no significant increase in the degree of degradation was achieved. The highest PCB degradation efficiency of 87.58% after 60 minutes was obtained at a peroxide concentration of 24.71mM and PCB concentration of about 40 ppm. The initial pH of the solution also proved to have an effect on PCB degradation. Highest oxidation efficiency of 87% was obtained at pH 7 after 60 minutes at a peroxide concentration of 24.71 mM. For the effect of initial concentration of PCBs, up to a certain concentration, degradation was found to increase with increasing PCB concentration. Highest degradation efficiency of 68% and 86% after 30 and 60 minutes, respectively, were obtained at a PCB concentration of 40 ppm. A decrease in degradation efficiency was, however, observed at 80 ppm which gave a lower degradation efficiency of 79% after 60 minutes of reaction In all the runs conducted, dechlorination is the main mechanism verified by GC-MS analysis.
The use of UV/H2O2 for PCB degradation seems very promising in the treatment of wastewater containing PCBs. The results of this study are highly significant in performing a kinetic analysis on PCB degradation. Current efforts involves improvement of the process.
The decomposition of Reactive Red 141 dye wastewaters by photolysis and VUV/H2O2 process with a 185nm Vacuum-UV lamp in a batch photoreactor was studied under various initial concentrations of organics, solution pH values, dosages of H2O2, and purging gases (N2, O2, and air). The photolytic properties of Red 141 were found to be highly dependent on the solution pH. For the VUV/H2O2 system, the individual contribution to the decomposition of Red 141 by direct photolysis, and free hydroxyl radicals destruction generated from the excitement of O2, H2O, and H2O2 by an 185nm VUV lamp, respectively was differentiated by the proposed assumption. Experimental results for the VUV-only system revealed that photolytic rates of organics by purging O2 were apparently larger than those by purging N2 and the removal of Red 141 was found to be above 90%. For the VUV/H2O2 process, the reaction rates were significantly raised compared with those by direct photolysis. The individual contribution on the decomposition of Red 141 by OH. destruction generated from the excitement of H2O2 molecules was found to be higher than 50% at low pH range (pH=3) in VUV/H2O2 system, however, only 30% at high pH range (pH=11) probably because of the production of hydroxyl radicals from the H2O2 excitement was hampered by the alkaline catalytic reaction between the molecules of H2O2 and HO2-.
Pulsed lamps which irradiates ultraviolet(UV) in high luminance has been developed. The experiment to inactivate of cryptosporidium parvum was conducted with the pulsed lamp. Also the effect of inactivate to high turbidity solution was investigated. The experiment examined the comparison and the evaluation methods (growth vitality assays and infectivity assays) with other kinds of UV lamps. As a result, higher capability of the pulsed lamp was demonstrated in the high UV dose area, compared to other UV lamps. The difference between inactivation efficiencies by the low pressure mercury lamp, the medium pressure mercury lamp and the pulsed lamp was not significant in the effect of inactivate to high turbidity solution. However, the tailing phenomenon was not observed with the pulse lamp while it was with the low pressure mercury lamp and the medium pressure mercury lamp when evaluating by excystation method. Moreover, sensitivity of cryptosporidium parvum to UV irradiation was in the order of the cell culture method, the mouse infection method, and excystation method in this experiment.
Three turbid substances were added to suspensions of Cryptosporidium parvum oocysts, and changes in the degree of ultraviolet (UV) inactivation of the C. parvum oocysts were evaluated by in vitro excystation and animal infectivity. Because the dose distribution of UV irradiation delivered to oocysts in turbid water may vary according to the degree of movement of the water, experiments were performed under vigorously mixed (completely mixed) conditions and stationary conditions. The estimated kinetic inactivation rate in the completely mixed system of turbid water (190 ntu) was 4.058 cm2/mJ, which was only 15% less than that in pure water (4.690 cm2/mJ). The estimated relative infectivity in the stationary system differed markedly from that obtained by regression of the plot of UV irradiation dose versus relative infectivity in pure water. Nevertheless, values of the relative infectivity obtained in animal experiments were nearly in agreement with the calculated values. In other words, despite decreases in the dose of UV delivered to oocysts under the influence of turbid substances, the efficacy of UV in inactivation of oocysts in turbid water was almost equal to that in pure water when expressed as per unit dose. Consequently, it became evident consequently that if the dose of UV delivered to oocysts was known, the degree of expected inactivation could be estimated. In addition, we added substances that adhere to the surface of C. parvum oocysts (humin and kaoline) to suspensions of C. parvum oocysts and studied the degree of UV inactivation. Adhesion of humin or kaoline particles to the oocyst wall resulted in a reduction in UV inactivation. However, the magnitude of the log10 inactivation in a suspension containing humin or kaoline particles was only about 20% and 10%, respectively, less than that in pure water.
Under UV irradiation, titanium dioxide (TiO2) exhibits a strong bactericidal activity through the generation of hydroxyl radicals (•OH). Silver (Ag) sensitization is an effective way to enhance photocatalytic activity of TiO2. In the present study, Micrococcus lylae was used as a model bacterium to compare the bactericidal activity of Ag-sensitized TiO2 (in two different Ag/TiO2 molar ratios) and pure TiO2 (P25). When the concentration of photocatalysts was fixed on 0.2 mg/ml with 300 rpm stirring, no obvious difference observed among the three photocatalysts. However, the Ag-sensitized photocatalysts with higher Ag/TiO2 ratio showed better bactericidal efficiency when their concentration decreased (0.1 mg/ml) or the stirring speed increased (380 rpm). The results indicated that optimizing the phosico-chemical conditions of reaction promoted the efficiency of photocatalyst. Moreover, transmission electron microscopy (TEM) was used to observe the sub-cellular structural changes of M. lylae during photocatalytic oxidation (PCO). According to the TEM images, the disruption of cell wall occurred at a relatively long time after the cell death. The cause of cell death was the destruction of plasma membrane induced by membrane permeable •OH. These results supported that both modification on photocatalyst properties and optimization on reaction conditions enhanced the bactericidal efficiency of PCO.
A pure culture of Microcystis aeruginosa (NIES-98) was exposed to low-pressure (LP) or medium-pressure (MP) UV lamps and subsequently incubated under white light fluorescent lamps allowing both photoreactivation and photosynthesis. During incubation, profiles of the number of existing cells and UV-induced DNA damage were determined for each sample. The growth of Microcystis aeruginosa was inhibited by the exposure to LPUV or MPUV. Only a minor difference was observed between LPUV and MPUV both in the cell number and the DNA damage. UV-induced DNA damage just after UV irradiation was almost the same regardless of the UV fluence or the UV lamp. Meanwhile, the UV-induced DNA damage was repaired during 1day incubation after UV exposure, and the number of DNA damage appeared somehow proportional to the UV fluence after 1day incubation. A comparison between the cell number and the number of DNA damage implied that the UV-induced DNA damage mainly contributed to the cell number reduction of Microcystis aeruginosa.
The Odaiba Marine Park is a typical sightseeing place that represents Tokyo. But unfortunately the Odaiba Marine Park is not in comfortable condition for the people dabbling in seawater, because of the increase of fecal coliforms due to the CSO (Combined Sewer Overflow) system after heavy rain. Tokyo Metropolitan Government started the ocean area purification experiment with EBARA Corporation. The filtration and the ultraviolet ray disinfection were adopted for the seawater purification process. The purification zone in the Odaiba Marine Park was partitioned with two oil fences, and the water from the purification plant was continuously drained off, at 5,000m3/day for three consecutive months. The purified seawater was discharged from July to October in 2003. Moreover, the effectiveness of photoreactivation, seen as the most challenging task when adopting disinfection by ultraviolet ray, is reported as the preliminary study conducted in 2002. The model tests, using seawater mixed with untreated sewage resulted in either a lower photoreactivation rate of the coliform groups, or further inactivation of the groups. This suggests that the coliform groups of the freshwater-origin are affected by salt density in the seawater with inhibition of the photoreactivation.
Recently, ultraviolet (UV) radiation has been applied as a disinfection method for wastewater treatment plants. A high-intensity and high-power UV light source is required in the field of bacilli sterilization. The electrodeless UV lamp turns on by delivering RF-frequency power from the power supply through the matching circuit into the induction coil around the lamp. The electric current passing through the induction coil generates a magnetic field. The gas sealed inside the lamp is excited and ionized by the magnetic field, and so discharge of the gas occurs and light is emitted. Thus the discharge produces UV emission. Using RF frequency power circuit technology and optimizing UV lamp shape, we have made it possible to input power of 500W to a 500mm-length luminescent lamp. Moreover, an over 30% rate of UV radiating efficiency has been obtained. It realizes a high-intensity and high-power ultraviolet light source. Optimization of water current path in the sewage effluent disinfection has realized a colon bacillus removal ratio of 99.9%.
In this paper the possibility of UV-reactor validation based on computational fluid dynamics will be discussed and related to biodosimetry and actinometry. Microbial inactivation depends on the UV-C dose that is described as UV intensity multiplied by exposure time. As a microbe enters a chamber containing UV lamps, it will receive varying irradiance levels from lamps depending on its distance from the lamp and the exposure time will depend on the specific path of the microbe through the reactor. It is necessary for UV-C dose calculation to determine the exposure time of a particular particle (microbe) and the UV intensity as function of position in the irradiation chamber based on the assumed UV-C power emission of the lamp. We can determine UV-C dose of a particular particle as function of position using the powerful software (3D Intensity calculation) supported by computational fluid dynamics. In order to calibrate CFD model, biodosimetric tests with the Bacillus subtillis spore were carried out in the four different reactors, each reactor equipped with 3, 4, 6 and 8 lumps respectively. It was founded that CFD model for UV reactor validation was in excellent agreement with the biodosimetric results. The actinometric tests with free chlorine were also undertaken to verify its possibility as alternative to the biodosimetry and the obtained results showed that the actinometry with free chlorine was a useful tool for determination of the average UV intensity in UV reactor.
Proving UV reactor performance through validation is becoming a common requirement in wastewater, reuse water and drinking water disinfection applications. However, there is often confusion in understanding the objectives of validation and when choosing an appropriate protocol to follow. This paper will visit the fundamental rationale behind validation. The primary principle behind performance validation is to ensure that public and environmental health is being safeguarded. To do this, regulations must set risk-based disinfection targets, and reactors must be shown to have adequate performance in terms of those targets. Validation must be based on empirical results to eliminate assumptions that are unsafe. Validation must be universal for a given reactor, so that it can be applied to any site where the reactor may be installed. Protocols must not be prescriptive with consequential hindrance to innovation, and they must not be too complex so that they can be accepted and implemented by the industry. This paper will expand on these major points, showing examples of how validation protocols can violate these principles, and also showing alternatives that uphold the principles, ensuring that public and environmental health is safeguarded.
This research examined the influence of nitrogen, acetate and propionate on hydrogen production from pineapple waste extract by photosynthetic bacteria strain Rhodospirillum rubrum in batch culture. The fermentation conditions used in this study were continuous illumination fermentation (24 hours of light) and periodic illumination fermentation (alternate 12 hours of light and dark). Two levels of total nitrogen (3 mM-low level and 11 mM-high level) with various initial concentrations of acetate or propionate (5, 10 and 20 mM) were added into the production medium. Results indicated that levels of total nitrogen did not affect the production of hydrogen. Neither acetate nor propionate was used as carbon source by R. rubrum but glucose contained in pineapple waste extract was used. Periodic illuminated fermentation was more effective in producing hydrogen than continuous illuminated fermentation. The maximum hydrogen production potential (337 ml), specific hydrogen production rate (11 ml/l/h), specific hydrogen production potential (247.75 ml H2/g COD) and hydrogen yield (122 ml H2/g glucose consumed) occurred upon addition of high level of total nitrogen (11 mM) with 5 mM initial concentrations of acetate under periodic illumination and a working volume of 40 ml. Results indicated that pineapple waste extract could be effectively used as substrate for hydrogen production by R. rubrum without any carbon and nitrogen sources.
The amount of excess sludge produced in municipal wastewater treatment plants in Japan is increasing every year as the urban population increases. Phosphorus in excess sludge could be a potential phosphorus resource since at present, phosphate rock is being exhausted all over the world. Every year, Japan imports large quantities of phosphorus from abroad but much are discharged as excess sludge. Therefore, solubilization process, one method of recovering phosphorus from sludge, could be a promising solution. In this study, subcritical water process, a new technology that solubilizes sludge under subcritical condition, was applied before the phosphorus in sludge was recovered with magnesium ammonium phosphate (MAP) process. As a result, the solubilization rate of excess sludge achieved approximately 80% and about 94-97% of the phosphorus could be recovered.
This research was conducted to investigate the capability of a coupling of activated sludge and microfiltration processes with backflushing technique to reduce organic carbon and color in textile wastewater. In this study, the optimum condition of membrane operation was obtained at 0.88 m/s cross-flow velocity (CFV) and 0.4 bar transmembrane pressure (TMP). On the other hand, the optimum condition of backflushing technique was obtained at 1.6 bar pressure applied for 1 second at 1.5-minute interval. With this optimum condition, the flux was relatively stable at 5.04 L/m2.h for all SRT. At steady state, the effluent COD decreased with increasing SRT. The COD removal was more than 82 % and color removal was more than 95 %. The microorganisms involved in the system were found to be slow-growing microorganisms. Therefore, the coupling of activated sludge and membrane separation processes successfully proceeded to treat textile wastewater. Complete solids removal as well as a significant degree of organic and color removal was achieved. Sludge production was also low amounting to less than 0.2 g dried cells/ g COD removed. Thus, the treatment of unsettled textile wastewater to a tertiary effluent quality in a single unit process was made possible.
Sewage water quality from Phnom Penh City in Cambodia was studied from December 1997 to September 1999. Samples were collected from the outfalls of sewer pipes to Tonle Sap River, channels, lakes, and pumping stations. As a result, concentrations of chemical oxygen demand (COD), total nitrogen (T-N) and total phosphorus (T-P) in dry season were much higher than those of surface water in Cambodia, possibly due to the domestic wastewater. In rainy season, these amounts decreased due to attenuation by the rainwater. In dry season, 56% of suspended solid (SS) in sewage deposited as sediments in channels and lakes. The levels of Cd, Zn, Cu and Pb in the sediments of these channels and lakes were higher than those in other points of the area studied. In rainy season, SS and heavy metals were flushed outside by the rainwater. Levels of anionic and nonionic surfactants, total organic halogen (TOX) and Bisphenol-A were found to those in Japan. Both surfactants mainly came from domestic wastewater while TOX and Bisphenol-A came from specific emission sources. Daily pollutant loads of SS, COD, T-N, T-P, anionic surfactant and nonionic surfactant were 13, 53, 8.2, 1.1, 1.4 and 0.3 (g/person-day), respectively.
The present study aimed to develop an effective extraction method for bioflocculants from activated sludge. Microbial polymers obtained from activated sludge by four different extraction methods (steaming, NaOH, SDS and washing extractions) were compared in terms of yield, chemical components, and flocculating activity for kaolin clay suspension. NaOH extraction has the highest yield, while washing extraction resulted to the lowest. The main component of the polymers obtained was protein, involving saccharide and nucleic acid, although the contents were varied considerably for individual polymers. All polymers possessed flocculating activity for kaolin clay containing cations, although the degree of activity varied significantly with extraction method. The activity of the polymer extracted with NaOH was the highest, while the activity of the polymer extracted with washing was the lowest. Among the cations tested, calcium and magnesium ions promoted activity. These results indicate that NaOH extraction was the most effective method for the extraction of bioflocculants from activated sludge.