Treatability of cefazolin antibiotic formulation effluent with O3 and O3/H2O2 processes.

The effect of applying ozonation and perozonation to antibiotic cefazolin-Na formulation effluents were investigated in this study. Twenty minutes of ozonation at a rate of 1,500 mg/L-h was observed to remove COD by 38%, whereas a COD removal efficiency of 40% was achieved via H2O2 enhanced ozonation (same conditions + 31.25 mM H2O2). Both of the pretreatment alternatives were monitored to elevate the BOD5/COD ratio from 0.01 to 0.08. The initially inert COD was reduced by 38% using ozonation and by 60% employing H2O2 enhanced ozonation. In terms of the lowest achievable effluent COD levels after bio-treatment, ozonation was observed to yield a residual COD of 205 mgL(-1), while a residual COD of 135 mgL(-1) was involved for perozonation. According to the results of acute toxicity on Phaedactylum tricornutum, ozonated and perozonated samples exhibited more toxicity than the untreated effluent after 4 days. The activated sludge inhibition test demonstrated that both of the pretreatment alternatives efficiently eliminated the inhibition of investigated formulation effluent.     

城市生活污水中的污染物分类及处理性评价

以城市生活污水为对象,通过长期取样和试验分析,研究了水中SS,COD,BOD,总磷,总氮等代表性污染物的存在形态和分布规律。以0.45μm作为溶解物和悬浮物界限尺寸的分析结果表明,城市生活污水中的SS,约65％的COD,60％的BOD,50％的磷和20％的氮均以悬浮物的形态存在,这部分污染物很容易通过沉淀或混凝沉淀的方法有效去除。在研究基础上提出的评价方法和污染物分类及处理性评价模式图有助于污水处理方法的合理选择。     

Extracellular polymers in partly ozonated return activated sludge: impact on flocculation and dewaterability.

The purpose of this study was to evaluate the influence of partial ozonation of return activated sludge on settling properties and dewaterability of sludge. Sequencing batch reactors with two sets of aerobic and alternating anoxic/aerobic conditions were used. In each set, one reactor served as a control and the other was subject to the ozone treatment (doses in the range of 0.016-0.080 mg O3/mg TSS of initial excess sludge). The level of total suspended solids (TSS) in each reactor was controlled at 1,800 mg/l. To evaluate settleability and dewaterability, settling kinetic studies, sludge volume index (SVI) and capillary suction time test (CST) were used. For extraction and quantifying sludge biopolymers, thermal-ethanolic extraction was employed. The ratio of bound-to-total extracellular polymer substances (EPS) was higher for the strictly aerobic reactor than for the alternating anoxic/aerobic one, indicating the stronger structure of the aerobic flocs. After ozone treatment, the fraction of bound EPS was released and solubilized, increasing soluble EPS. Increased apparent food-to-microorganism (F/M) ratio favoured production of EPS in ozonated reactors, enhancing flocculation, which had potential to improve settling. Dewaterability, measured by CST test, was better in alternating anoxic/aerobic reactors than in aerobic ones, indicating that incorporation of an anoxic zone for biological nutrient removal leads to improvement in sludge dewatering. The negative impact of ozonation on dewaterability was minimal in terms of the long-term operation.     

Secondary effluent reclamation: combination of pre-treatment and disinfection technologies.

A study was carried out to evaluate the efficiency of secondary effluent additional treatment, using a combination of pre-treatments (ring filter, physico-chemical and infiltration-percolation) followed by disinfection methods (chlorine dioxide, peracetic acid and ultraviolet light). Three different indicator microorganisms were determined: E. coli, total coliforms and somatic bacteriophages. The results show better efficiency of physico-chemical and infiltration-percolation processes. Bacteriophages were eliminated to a lesser extent than bacterial indicators in all the treatment systems. Chlorine dioxide and peracetic acid seems to be more efficient in disinfection than ultraviolet light when a ring filter is the pre-treatment used. For the same doses and contact times, the efficiency of the disinfection methods is higher when the pre-treatment used is the physico-chemical or the infiltration-percolation system. The final effluent quality from the physico-chemical treatment train and the infiltration-percolation treatment train, followed by the disinfectants, achieves an E. coli content that allows the reuse in most of the uses described in the Spanish legislation for wastewater reuse.     

Evaluation of MBR effluent characteristics for reuse purposes.

One of the advantages of MBR is its excellent effluent quality, which is suitable for a wide range of reuse purposes. We investigated the characteristics of MBR effluent and evaluated them based on the Japanese guideline for the reuse of treated wastewater. As the result, MBR effluent showed qualitative coaracteristics that satisfy the requirement except chromaticity for recreational purpose. Further treatment, such as by oxone or activated carbon, will be required to remove the remaining color. MBR shows high removal efficiency of bacteria and other hazardous microorganisms such as Cryptosporidium. We investigated the removal efficiency of virus by MBR using coliphage as an alternative index. The results showed that high removal efficiency for coliphage could be obtained by MBR. The removal mechanism appears to be that coliphage are attached to the activated sludge and thus rejected by the membrane together with activated sludge particles. With regard to the endocrine disrupters, no significant differences were observed between MBR and CAS in the removal of main endocrine disrupters.     

Disinfection and oxidation of sewage effluent water using ozone and UV technologies.

This study was aimed at exploring the reclamation of sewage treatment plant effluent water (SEW) as an alternative water resource. For the oxidation of SEW, an ozone-UV system, based on the results of the combined ozone/UV process performed in our previous study, was set up under practical conditions, including a series type, continuous mode, semi-pilot scale operation (1.5 m3/d). As a result, the serial contact of the ozone and UV reactors showed lower CODCr and TOC removal efficiencies. However, these were greatly enhanced by recycling the water flow of the ozone-UV system at 40Q, as a result of the improvements in the transferred ozone dose in the ozone reactor and the contact efficiency between photons and ozone in the UV reactor, which approached that achieved in the combined ozone/UV process. For the disinfection of SEW, carried out in a syringe-type batch reactor, the increase of instantaneous ozone demand (ozone ID) led to a higher inactivation efficiency, an increased UV transmittance due to ozonation, and an enhanced inactivation rate of E. coli in the UV reactor. Additionally, it was concluded that the ozone/UV process could overcome the limitations of the ozone alone and UV alone processes for the reclamation of sewage effluent water.     

Prevalence of human adenoviruses in raw and treated water.

Human adenoviruses (HAds), of which there are 51 antigenic types, are associated aetiologically with gastrointestinal, respiratory, urinary tract and eye infections. The clinical importance of HAds and the potential health risks constituted by HAds in water environments are widely recognised. This study was conducted to assess the use of an optimised integrated cell culture molecular-based technique to determine the prevalence of HAds in raw and treated drinking-water supplies in South Africa. Selected supplies were monitored weekly for the presence of adenoviruses over a one-year period (July 2001 to June 2002). Drinking-water supplies were derived from acceptable quality surface water sources using treatment processes that conformed to international standards for the production of safe drinking water. Adenoviruses were detected by amplification in cell cultures, followed by amplifying the extracted nucleic acids using molecular techniques (nested PCR). HAds were detected in 29.8% (59/198) of the treated drinking water, 16% (8/50) of dam water and 44% (22/50) of river-water samples tested. The results of this study confirmed the presence of HAds in some raw and treated drinking water supplies in South Africa.     

Advanced oxidation of bleached eucalypt kraft pulp mill effluent.

In this study a poorly biodegradable (BOD/COD = 0.3) industrial alkaline ECF bleaching filtrate was treated using different advanced oxidation processes to evaluate their use in combined chemical-biological treatment aimed at increasing recalcitrant COD removal and improving final effluent quality. Oxidative treatments included ozonation combined with hydrogen peroxide (2, 5, 10, 20 mmol L(-1) O3/0.7, 2, 5, 10 mmol L(-1) H2O2) and photocatalysis with hydrogen peroxide (UV/2, 4 and 8 mmolL(-1) H2O2) and with TiO2 (UV/TiO2/0.7 and 4 mmol L(-1) H2O2). The O3/H2O2 process increased effluent biodegradability by up to 68% as a result of increasing BOD and decreasing COD. Increasing the O3 dose had a greater effect on biodegradability improvement and lignin and colour removal efficiencies than increasing the H2O2 dose. A combined oxidant dose of 5 mmol L(-1) O3 and 2 mmol L(-1) H2O2 resulted in 75% lignin removal, 40% colour removal and 6% carbohydrate loss without mineralizing the organic carbon. The photocatalytic processes led to a decrease in effluent biodegradability through combined decrease in BOD and increase in COD and did not result in efficient lignin or colour removal. Photocatalytic oxidation was apparently inhibited by the high chloride and COD levels in the alkaline filtrate, and may be more efficient in recalcitrant COD removal if performed after biological.     

Continuous and sequencing membrane bioreactors applied to food industry effluent treatment.

This work focuses on the performances of two immersed membrane bioreactors used for the treatment of easily biodegradable organic matter present in food industry effluents, for the purpose of water reuse. Two reactor functioning modes (continuous and sequencing) were compared in terms of organic carbon removal and of membrane permeability. For each working mode, pollutant removal was very high, treated water quality presented a low COD concentration (< 125 mg x L(-1)), no solids in suspension and low turbidity (< 0.5 NTU). The quality of the treated water (including germ removal) enabled its reuse on site. Moreover, by developing high biomass concentrations in the reactor, excess sludge production remained very low (< 0.1 gVSS x gCOD(-1)). The performances appeared slightly better for the continuous system (lower COD concentration in the effluent, < 50 mg x L(-1), and lower sludge production). In terms of filtration, a distinct difference was observed between continuous and sequencing systems; transmembrane pressure showed a small and constant evolution rate in continuous membrane bioreactor (CMBR) although it appeared more difficult to control in sequencing membrane bioreactor (SMBR) probably due to punctually higher permeate flow rate and modified suspension properties. The rapid evolution of membrane permeability observed in SMBR was such that more frequent chemical cleaning of the membrane system was required.     

Activated sludge image analysis system: monitoring settleability and effluent clarity.

A fully automized image analysis procedure is presented for fast and reliable characterization of the activated sludge composition. In previous research, relations between filament abundance and floc shape on the one hand, and the Sludge Volume Index on the other hand were sought. This work aims at demonstrating the use of the image analysis information as an indication for the amount of suspended solids in the effluent.     

Effect of biomanipulation on the structuring of the planktonic food web and water treatability by coagulation

The impact of planktivorous fish on the plankton community structure and character of aquatic organic matter was studied by a meso-scale enclosure experiment in a stratified reservoir. Aims of the study were (i) to examine the response of the communities with and without herbivorous zooplankton to an increased input of phosphorus and (ii) to determine the composition and coagulation properties of the organic matter produced by these communities. T'he concentration and composition of organic matter were affected both in the enclosure with planktivorous fish (F), where high algal biomass developed, and in the enclosure without fish (Z), where algae were maintained at a low concentration by zooplankton grazing. Although differences between the enclosures in concentrations of total dissolved organic matter and its hydrophobic, hydrophilic and neutral/basic fractions were relatively small, coagulation properties of the organics differed substantially. Particulate and dissolved organic matter produced in enclosure F had a positive effect on the efficiency of alum coagulation in contrast to the less readily separable organics produced in enclosure Z. The results indicate that pelagic food web manipulations to maintainin low phytoplankton biomass by zooplankton grazing may not always have positive effects on the treatability of water by coagulation.     

Membrane fouling and selectivity mechanisms in effluent ultrafiltration coupled with flocculation.

Membrane filtration is adequate for producing disinfected clear water suitable for various kinds of applications. However, fouling of membranes is the main limitation. The scope of the present study is to examine the effect of iron coagulation of primary wastewater effluent on membrane filtration, in parallel to fouling characterization of the iron itself. The fouling of ultrafiltration membranes by colloidal iron hydroxide-oxide has been studied by measuring the pore streaming potential of PES UF membrane. pH 5.5 (charge neutralization zone) provided better removal and lower fouling intensity than pH 7.8 (sweep coagulation zone), but the internal clogging at acidic pH was higher. Fouling of the membrane as measured by flux reduction was usually accompanied by a positive change in zeta potential and iso-electric point (IEP) of the membrane. An initially large change in zeta potential (without charge reversal) was seen even after relatively small amounts of iron solution were filtered through the membrane. A control experiment showed this is not due to iron adsorption equilibrium, but should probably be attributed to fouling. Change in zeta potential, can be used as an indicator for commencement of fouling even for small flux reductions. UF membrane critical flux after iron filtration can be evaluated more accurately by zeta potential than pressure drop or change in iron concentration.     

Origins of filter effluent particles: experimental study of particle deposition and detachment.

This paper investigates the relative roles of particle deposition and detachment in controlling the origin of filter effluent particles. A conceptual mathematical model was developed and laboratory-scale experiments were conducted. Laboratory experiments were performed using three sizes of fluorescent microspheres (FMs), to determine the fraction of filter effluent particles that are filter influent particles that were never removed, as well as the fraction of filter effluent particles that were detached after deposition. Experimental results indicated that particle detachment is significant beginning from the early phase of filtration. FM removal increased with filter run time, depth and particle size. For each size FM at one filter depth, FM removal increased with filter runtime to a maximum due to ripening and then decreased with filter runtime after ripening due to limited pore space remaining in the filter. The fraction of effluent particles that were detached particles increased with particle size and filter bed depth.     

Development of a monitor to simultaneously measure dissolved ozone and organic matter in ozonated water

A method for measuring both dissolved ozone (DO₃) concentration and UV absorbance was developed adopting ultraviolet (UV) absorption method (Japan Water Works Association (JWWA), 1993a, Japan Water Works Association (JWWA), 1993b) using sodium thiosulfate (Na₂S₂O₃) solution for removing residual ozone in ozonated water. A DO₃ monitor based on this method was tested. This method was proven to be effective from experimental results. The performance of the monitor was examined with continuous ozonated water. As a result, the monitor performed stably during about 2 months, so that both DO₃ concentration and UV absorbance in the ozonated water could be accurately measured. Therefore, the authors have proposed the new aquatic control system with this monitor for ozonation.     

Treatment of municipal wastewater UASB reactor effluent by unconventional flotation and UV disinfection.

Post-treatment of an UASB reactor effluent, fed with domestic sewage, was conducted using two-stage flotation and UV disinfection. Results were compared to those obtained in a parallel stabilisation pond. The first flotation stage employed 5 - 7.5 mg L(-1) cationic flocculant to separate off more than 99% of the suspended solids. Then, phosphate ions were completely recovered using carrier flotation with 5-25 mg L(-1) of Fe (FeCl3) at pH 6.3-7.0. This staged flotation led to high recoveries of water and allowed us to separate organic matter and phosphate bearing sludge. The water still contained about 1 x 10(2) NMP/100 mL total coliforms, which were removed using UV radiation to below detection levels. Final water turbidity was < 1.0 NTU, COD < 20 mg L(-1) O2 and 71 mNm(-1), the liquid/air interfacial tension. This flotation-UV flowsheet was found to be more efficient than the treatment in the stabilisation pond and appears to have some potential for water reuse. Results were discussed in terms of the biological, chemical and physicochemical mechanisms involved.     

Benchmarking of WWTP design by assessing costs, effluent quality and process variability.

Process choice and dimensioning of WWTPs is a particularly sensitive step to cost-efficiently comply with regulatory standards. This step accounts only for a small fraction of the upfront costs, but it can lead to substantial savings. This paper illustrates the results of a systematic methodology to evaluate system design/upgrade options. In contrast to conventional practice, this approach allows the choice between the most appropriate trade-off between cost of measures and effluent quality, and to assess the reliability of a process layout. It is therefore a flexible instrument to cope with the flexibility and complexity of integrated water management regulations. Results show good agreement of the simulations with extensiv benchmarking studies on actual plants. For that reason, the suggested methodology can provide valuable support also to such practices.     

Multi-component kinetics of activated sludge treatment of bleached kraft mill effluent.

This study investigated the discrepancies between the BOD removal rates measured during short term assays and those measured during continuous activated sludge treatment of bleached kraft mill effluent (BKME). A combination of batch tests and fed batch tests with oxygen uptake rate (OUR), chemical oxygen demand (COD), biochemical oxygen demand (BOD), and mixed liquor volatile suspended solids (MLVSS) measurements were used to characterize the degradation rates for the activated sludge treatment of BKME and to divide the soluble readily biodegradable substrate into two to five separate fractions based on biodegradation rates. The removal rates varied by over an order of magnitude between the most readily degradable substrates (1 x 10(-3) mg COD/mg MLVSS minute), and the more slowly degradable substrates (2 x 10(-5) mg COD/mg MLVSS minute). If the readily biodegradable fraction of BKME was modeled as one substrate, initial rate kinetic measurements from batch tests were heavily influenced by the fractions with the greatest degradation rates, while any remaining BOD in the treated effluent was predominantly from the slowly degradable fraction, giving inconsistent results. Taking the multi-component nature of the wastewater into account, batch test results can be used to predict fed-batch and continuous activated sludge reactor performance.     

Treatment of nitrogen and phosphorus in highly concentrated effluent in SBR and SBBR processes.

Various sludge treatment processes produced supernatant with high ammonia concentration from 500 to 2,000 mgN/L and generally high phosphate concentration. Conversion of ammonia into nitrite via partial nitrification has proven to be an economic way, reducing oxygen and external COD requirements during the nitrification/denitrification process. Two processes with biomass retention are studied simultaneously: the sequencing batch reactor (SBR) and the sequencing batch biofilm reactor (SBBR). At a temperature of 30 degrees C, the inhibition of nitrite-oxidizing bacteria due to high ammonia concentration has been studied in order to obtain a stable nitrite accumulation. This work has confirmed the effect of pH and dissolved oxygen on nitrite accumulation performance. During a two month starting period, both processes led to nitrite accumulation without nitrate production when pH was maintained above 7.5. From a 500 mgN/L effluent, the performance of the SBR, and the SBBR, reached respectively about 0.95gN-NO2-/gN-NH4+, and 0.4gN-NO2-/gN-NH4+. The SBBR appears to be more stable facing disturbances in dissolved oxygen conditions. Finally, the maximal phosphate removal rates obtained in the SBR reached 90%, and 70% in the SBBR, depending on ammonium accumulation in the reactor. Ammonium phosphate precipitation is likely to occur, as was suggested by crystals observation in the reactor.     

Ozonation parameter for removal of oestrogenicity from secondary effluent without by-products.

The purposes of this study are to investigate ozonation characteristics, to evaluate oestrogenicity and to confirm behaviours of by-products during ozonation of secondary effluent. For the ozonation of secondary effluent, TOC was decreased only 10% when 4 (mgO3/mgC) of ozone consumption per initial TOC. However, UV254 and SUVA was decreased approximately 65% until ozone consumption of 2 (mgO3/mgC). Ozonation was also shown to be very effective for decrease of oestrogenicity in secondary effluent. Bromate ion started to form obviously when the ozone consumption per initial TOC exceeded 2 (mgO3/mgC) and increased while the time of ozonation became longer. From these results, ozone consumption per initial TOC was shown to be an appropriate operation parameter to reduce SUVA effectively and E2 equivalent concentration to less than 0.1 nM without significant formation of bromate ion, and its value was determined to be 2 (mgO3/mgC) in ozonation of secondary effluent.     

Combined chemical biological treatment of bleached eucalypt kraft pulp mill effluent.

Effectiveness of ozonation before and after biological treatment for removal of recalcitrant organic matter in bleached kraft pulp effluents was compared. Two industrial ECF bleached eucalypt kraft pulp effluents (E1 and E2) were pretreated with 100 mg O3/L. Raw and pretreated effluents were treated biologically in bench-scale sequencing batch reactors, under constant conditions. Following biological treatment, effluents were post-treated with 100 and 200 mg O3/L. Effluent pretreatment increased effluent biodegradability by 10% in E1 and 24% in E2. Combined O3-biological treated led to small but significant increases in COD, BOD and lignin removal over biological treatment alone, but pretreatment had no significant effect on effluent colour and carbohydrate removal. Ozone pretreatment did not affect biological activity during treatment of effluent E1 but resulted in a 38% lower specific oxygen uptake rate in effluent E2. At an equivalent dose of 100 mg/L, pre-ozonation produced better quality effluent than post-ozonation, especially with regard to COD and colour. Likewise, when an equivalent dose of 200 mg/L was applied, splitting the dose equally between pre- and post-treatments was more efficient than applying the entire dose in the post-treatment. The potential for combined chemical-biological treatment to improve effluent quality has been confirmed in this study.