Performance evaluation of physicochemical processes for biologically pre-treated livestock wastewater.

The use of a combination of biological and physicochemical methods is a promising technique to reduce highly concentrated pollutants in livestock wastewater: firstly, biodegradable organic matters, nitrogen and a part of phosphorus should be removed in a biological treatment process and then residual non-biodegradable organic matters, color and phosphorus be eliminated by physicochemical methods. In this study, therefore, the integrations of chemical coagulation, activated carbon adsorption, Fenton oxidation and ozonation were evaluated to provide an appropriate post-treatment process for biologically pre-treated livestock wastewater. With applying a single method such as coagulation and Fenton oxidation, a yellowish brown color and COD still remained. According to the experimental result, the quality of treated wastewater including color was enough to be discharged after chemical coagulation followed by ozonation or Fenton oxidation process. Among these, ozonation was the most effective technology for decolorization. Neither simple biological nor physicochemical process provides an adequate treatability for the sufficient depletion of organics and decolorization when treating livestock wastewater. Considering only the removal efficiency, the integration of Fenton oxidation and ozonation would be an efficient alternative as a post-treatment.     

A membrane biofilm reactor achieves aerobic methane oxidation coupled to denitrification (AME-D) with high efficiency

Methane would potentially be an inexpensive, widely available electron donor for denitrification of wastewaters poor in organics. Currently, no methanotrophic microbe is known to denitrify. However, aerobic methane oxidation coupled to denitrification (AME-D) has been observed in several laboratory studies. In the AME-D process, aerobic methanotrophs oxidise methane and release organic metabolites and lysis products, which are used by coexisting denitrifiers as electron donors for denitrification. Due to the presence of oxygen, the denitrification efficiency in terms of methane-to-nitrate consumption is usually low. To improve this efficiency the use of a membrane biofilm reactor was investigated. The denitrification efficiency of an AME-D culture in (1) a suspended growth reactor, and (2) a membrane biofilm reactor was studied. The methane-to-nitrate consumption ratio for the suspended culture was 8.7. For the membrane-attached culture the ratio was 2.2. The results clearly indicated that the membrane-attached biofilm was superior to the suspended culture in terms of denitrification efficiency. This study showed that for practical application of the AME-D process, focus should be placed on development of a biofilm reactor.     

Potential of UV/H2O2 oxidation for enhancing the biodegradability of municipal reverse osmosis concentrates

UVC/H2O2 and VUV/H2O2 oxidation processes were evaluated for the degradation of organic pollutants in reverse osmosis concentrate (ROC) produced from a municipal secondary effluent. It was found that the oxidation by UVC/H2O2 and VUV/H2O2 processes could be described as a pseudo first-order reaction. For UVC increased oxidation occurred with increasing H2O2 dosage up to 2 mM above which improvement in oxidation performance decreased. At the same H2O2 dosage, VUV irradiation gave better overall oxidation performance. Compared with UVC/6 mM H2O2, VUV/2 mM H2O2 gave a greater rate of reduction of chemical oxygen demand, but a lower rate for reduction of dissolved organic carbon, suggesting that oxidation of organics by the two methods followed different pathways. The change of absorbance at 254 nm and fluorescence excitation emission matrix spectra of irradiated samples indicated that the large and complex compounds were fragmented rapidly by the *OH, resulting in rapid decolourisation. The biodegradability of the organics in the ROC was increased from 11% to 35% after 1 h treatment by UVC/3 mM H2O2, whereas a greater increase (41%) was obtained with VUV/2 mM H2O2. This increase in biodegradability indicates the potential for employing a subsequent biological treatment process.     

Removal of volatile organic compounds by heterogeneous ozonation on microporous synthetic alumina silicate

A hybrid process combining adsorption and ozonation was examined as an alternative treatment for odorous volatile organic compounds (VOCs). Methyl ethyl ketone (MEK) was chosen to study the influence of operating parameters. Two synthetic aluminosilicates (faujasite-Y and ZSM-5) were tested for adsorption and reactivity with ozone. The adsorption equilibrium measurement on both adsorbents showed that adsorption performance depends on temperature but is not sensitive to relative humidity, due to the hydrophobic properties of the materials. Adsorbed VOCs were oxidized at low temperature when ozonated flow was sent to the reactor. Regeneration of the fixed bed was achieved at the same time, releasing mainly CO(2) and H(2)O. Intermediates of oxidation, such as 2,3-butanedione and acetic acid, were identified, leading to incomplete mineralization. The influence of concentration and humidity are discussed. Four successive cycles were tested: after the first adsorption/ozonation cycle, the adsorption efficiency was not affected during subsequent cycles. These results show that the same sample of adsorbent can be used in the treatment process for a long time. Ozonation regeneration is a promising process for VOC removal.     

Nitrogen removal from the saline sludge liquor by electrochemical denitrification.

Sludge liquor from the sludge dewatering process has a high ammonia content. In the present study, a lab-scale electrochemical (EC) system with a pair of Ti electrode plates was used for treating the sludge centrate liquor of digested wastewater sludge with a NH4(+) - N content of around 500 mg/L. The sludge liquor had a high salinity due to seawater being used for toilet flushing in Hong Kong. The results show that the EC process is highly effective for denitrification of the saline sludge liquor. Complete nitrogen removal could be achieved within 1 hr or so. The rate of EC denitrification increased with the current intensity applied. The best current efficiency for nitrogen removal was obtained for a gap distance between the electrodes at 8 mm. Electro-chlorination was considered to be the major mechanism of EC denitrification. The formation of chlorination by-products (CBPs) appeared to be minimal with the total trihalomethanes (THM) detected at a level of 300 microg/L or lower. The power consumption for EC denitrification was around 23 kWh/kg N. Additional electro-flocculation with a pair of iron needle electrodes could enhance the flocculation and subsequent sedimentation of colloidal organics in the sludge liquor, increasing the organic removal from less than 30% to more than 70%. Therefore, the EC process including both electro-denitrification and electro-flocculation can be developed as the most cost-effective method for treatment of the saline sludge liquor.     

Strong nitrogenous and agro-wastewater: current technological overview and future direction.

Nitrogen input to our environment has increased tremendously during the last four decades. It has been recognized that most of the nitrogenous wastes are produced from animal farms and agro-industries, which discharge a large amount of nitrogen as well as organics. Various biological and physico-chemical means are considered or applied for nitrogen removal. Particularly, biological nitrite nitrification and denitrification, and struvite precipitation have received more attention as applicable processes for strong nitrogenous waste treatment. The advanced oxidation process appears to be more attractive than activated carbon adsorption in terms of the removal of refractory organics when a further treatment of biologically treated effluent is required. Technologies using membrane bioreactors were very effective for solids separation, while reverse osmosis was found to be efficient for water reuse purpose with sufficient removal of refractory organics and nitrogen along with biological treatment. Reuse or recycling of strong nitrogenous wastes and agro-wastewater will be a desirable direction for the future in order to prevent the nitrogenous and organic pollution.     

Development of a hybrid ozonation biofilm-membrane filatration process for the production of drinking water.

Drinking water sources in Norway are characterized by high concentrations of natural organic matter (NOM), low alkalinity and low turbidity. The removal of NOM is therefore a general requirement in producing potable water. Drinking water treatment plants are commonly designed with coagulation direct filtration or NF spiral wound membrane processes. This study has investigated the feasibility and potential of a hybrid process combining ozonation and biofiltration with a rotating disk membrane for treating drinking water with high NOM concentrations. Ozonation will oxidize the NOM content removing colour and form biodegradable organic compounds, which can be removed in biological filters. A constructed water was used in this study which is representative of ozonated NOM-containing water. A rotating membrane disk bioreactor downstream the ozonation process was used to carry out both the biodegradation as well as biomass separation in the same reactor. Maintenance of biodegradation of the organic matter while controlling biofouling of the membrane and acceptable water production rates was the focus in the study. Three operating modes were investigated. Removal of the biodegradable organics was consistent throughout the study indicating that sufficient biomass was maintained in the reactor for all operating conditions tested. Biofouling control was not achieved through shear-induced cleaning by periodically rotating the membrane disks at high speed. By adding a small amount of sponges in the membrane chamber the biofouling could be controlled by mechanical cleaning of the membrane surface during disk rotation. The overall results indicate that the system can favorably be used in an ozonation/biofiltration process by carrying out both biodegradation as well as biomass separation in the same reactor.     

Photocatalytical polishing of paper-mill effluents.

Photocatalytic oxidation (PCO) is a promising technology for purification of biological pretreated wastewater or destruction of non-biodegradable compounds. For this reason PCO has been investigated as a last step of purification of biologically pre-treated paper-mill effluents. The influence of the parameters pH, TiO2-modification, TiO2-concentration, catalyst re-use, concentration of substances to be oxidised (wastewater quality) has been determined. The TOC of the biologically pretreated wasterwater was up to 55 mg L(-1). This wastewater was treated with a previously presented aerated cascade photoreactor which was modified for batch experiments. A high specific oxidation rate of up to 0.76 g TOC m(-2) h(-1) as well as a complete TOC mineralization has been achieved after the optimisation of the process parameters. The complete destruction of recalcitrant compounds will offer the opportunity to reuse the wastewater in the production process. The increase of the BOD5/TOC ratio after a short irradiation period indicates the transformation of recalcitrant organic compounds to better biodegradable intermediates. The use of PCO as a pre-treatment step for the enhancement of the biodegradability of wastewater, containing recalcitrant or inhibitory compounds is an alternative to a long and energy-intensive total pollutant mineralization.     

Development of an ecologically sustainable wastewater treatment system

The present study aimed mainly for the development of a wastewater treatment system incorporating enhanced primary treatment, anaerobic digestion of coagulated organics, biofilm aerobic process for the removal of soluble organics and disinfection of treated water. An attempt was also made to study the reuse potential of treated water for irrigation and use of digested sludge as soil conditioner by growing marigold plants. Ferric chloride dose of 30 mg/l was found to be the optimum dose for enhanced primary treatment with removals of COD and BOD to the extent of 60% and 77%, respectively. Efficient anaerobic digestion of ferric coagulated sludge was performed at 7 days hydraulic retention time (HRT). Upflow aerobic fixed film reactor (UAFFR) was very efficient in removals of COD/BOD in the organic loading rate (OLR) range of 0.25 to 3 kg COD/m(3)/day with COD and BOD removals in the range 65-90 and 82-96, respectively. Photo-oxidation followed by disinfection saved 50% of chlorine dose required for disinfection of treated effluent and treated water was found to be suitable for irrigation. The result also indicated that anaerobically digested sludge may be an excellent soil conditioner. From the results of this study, it is possible to conclude that the developed wastewater treatment system is an attractive ecologically sustainable alternative for sewage treatment from institutional/industrial/residential campuses.     

Using ozone to reduce recalcitrant compounds and to enhance biodegradability of pulp and paper effluents.

The effect of ozone based oxidation on removing recalcitrant organic matter (ROM) and enhancing the biodegradability of alkaline bleach plant effluent was investigated. A bubble column ozonation tower was used in the study. The experiments were carried out at different temperatures (20 degrees C and 60 degrees C) and pH (9 and 11), with a number of biological and chemical parameters being monitored including BOD5, COD, TC, pH, color, and molecular weight distribution of organics (nominal cut off of 1,000 Da). Biodegradability of the effluent was determined based on BOD5/COD of the wastewater throughout the process. For all the experiments, ozonation enhanced the biodegradability of the effluent by 30-40%, which was associated with noticeable removal of ROM including high molecular weight (HMW) and color-causing organics by about 30% and 60%, respectively. While the biodegradability of HMW fraction increased by about 50%, there was no biodegradability improvement for low molecular weight (LMW) portion, which was originally readily biodegradable (with BOD5/COD of about 0.5). Statistical analysis of variance (ANOVA) revealed neither pH nor temperature played significant role on the ozonation process at 95% confidence level.     

Analysis of build-up of heavy metals and volatile organics on urban roads in gold coast, Australia

Urban water quality can be significantly impaired by the build-up of pollutants such as heavy metals and volatile organics on urban road surfaces due to vehicular traffic. Any control strategy for the mitigation of traffic related build-up of heavy metals and volatile organic pollutants should be based on the knowledge of their build-up processes. In the study discussed in this paper, the outcomes of a detailed experimental investigation into build-up processes of heavy metals and volatile organics are presented. It was found that traffic parameters such as average daily traffic, volume over capacity ratio and surface texture depth had similar strong correlations with the build-up of heavy metals and volatile organics. Multicriteria decision analyses revealed that that the 1-74 microm particulate fraction of total suspended solids (TSS) could be regarded as a surrogate indicator for particulate heavy metals in build-up and this same fraction of total organic carbon could be regarded as a surrogate indicator for particulate volatile organics build-up. In terms of pollutants affinity, TSS was found to be the predominant parameter for particulate heavy metals build-up and total dissolved solids was found to be the predominant parameter for the potential dissolved particulate fraction in heavy metals buildup. It was also found that land use did not play a significant role in the build-up of traffic generated heavy metals and volatile organics.     

Framework for assessment of performance of soil aquifer treatment systems.

Removal of organic matter is a critical parameter in soil aquifer treatment (SAT) as it governs and influences the removal of other contaminants by biodegradation namely trace organics, nitrogen species and microbes. A framework for analysis and prediction of the performance of SAT systems with respect to removal of organic matter under different water quality and process conditions was developed based on an extensive literature review and data analysis. Guidelines were developed to make preliminary estimates of the removal of organic matter during SAT using primary, secondary and tertiary effluents from wastewater treatment plants. These guidelines can be used as a quick tool to analyze the performance of existing SAT systems and serve as a decision support tool for feasibility studies and to save time for further detailed experimentation and design of SAT systems. Furthermore, effects of soil type and redox conditions on organic matter removal during SAT were also analyzed.     

Removal of endocrine disruptors using homogeneous metal catalyst combined with nanofiltration membrane.

Chemicals that are known or suspected of being endocrine disrupting chemicals (EDCs) have received increased attention over the past decade for their potential presence in drinking water sources. This study focuses on the development of a hybrid system that combines the advantages of nanofiltration (NF) and homogeneous catalytic oxidation, which include compactness, operational facilitation, high treatment efficiency, and selective reaction capability. Iron(lll)-tetrasulfophthalocyanine (Fe-TsPc) was employed as a homogeneous metal catalyst to degrade bisphenol-A (BPA), a representative EDC. The treatment efficiency of BPA as well as operational characteristics of the hybrid system was investigated to examine the applicability of this technique to decrease the concentration of EDCs in drinking water. Fe-TsPc homogeneous catalyst revealed a remarkable activity in degrading BPA under acidic condition. The high rejection of Fe-TsPc catalyst in the feed stream by the membrane for its large molecular weight (976 Da) and functional group (SO3(-) X4) allowed the continuous use of the catalyst for BPA oxidation reaction. The NF with Fe-TsPc/H2O2 hybrid system turned out to have higher BPA treatment efficiency comparing with the NF-only system since the hybrid system reduced BPA concentration in the feed stream by catalytic destruction of BPA as well as it mitigated concentration polarization on the surface of the membrane.     

Development of a confined water sensitive urban design (WSUD) system using engineered soils.

Innovative Water Sensitive Urban Design (WSUD) systems are being investigated at three locations to the north and south of Sydney, Australia. These systems contain porous concrete pipes that are designed so that stormwater exfiltrates through the permeable walls of the pipes into the surrounding substrate media material. The porous pipes and media material treat the passing stormwater. The primary aim of the overall project is to develop a model to describe the treatment effectiveness of confined WSUD systems. This paper focuses on the system located at the Weathertex Industrial Site, Heatherbrae. Due to wood processing operations that occur at this site, it is recognised that the surface runoff will carry a heavy organics loading. Granulated Activated Carbon (GAC) is recognised for its ability to reduce the concentration of dissolved organics present in both wastewater and stormwater. GAC was therefore chosen as a filtration medium to be investigated at this site. To maximise the effectiveness of the GAC, extensive laboratory batch studies were undertaken prior to the field system being constructed to determine the optimum GAC/sand ratio. The purpose of the experimental work was to assess the dissolved organic removal potential through sorption of various concentrations of GAC. The aim of this paper is to describe these laboratory experiments and discuss how they related to the field system. Through these experiments it was determined that a sand/GAC ratio of 25:1 was ideal for the media material at the Heatherbrae site.     

Aqua-Biomant: integrated biological and electrochemical oxidation for industrial wastewater treatment.

An innovative technology for industrial wastewater treatment has been developed. The main focus of the new system is a transformation of persistent organic compounds (biorecalcitrant COD) into a biodegradable fraction, followed by high efficient biological elimination using specialised bacteria's. To fulfill these targets the Aqua-Biomant process integrates two treatment steps: an aerated biological upflow filter and a electrochemical oxidation technique using boron doped-diamond electrodes. The advantages of the process are high efficient COD removal with reduced energy consumption combined with low total residence time.     

Use of electrochemical oxidation process as post-treatment for the effluents of a UASB reactor treating cellulose pulp mill wastewater.

The main purpose of this study was to evaluate the performance of the electrochemical oxidation process as a post-treatment for the effluents of a bench-scale UASB reactor treating simulated wastewater from an unbleached pulp plant. The oxidation process was performed using a single compartment cell with two plates as electrodes. The anode was made of Ti/Ru0.3Ti0.7O2 and the cathode of stainless steel. The following variables were evaluated: current density (75, 150 and 225 mA cm(-2)) and recirculation flow rate in the electrochemical cell (0.22, 0.45 and 0.90 L h(-1)). The increase in current density from 75 to 225 mA cm(-2) did not increased the color removal efficiency for the tested flow rates, 0.22, 0.45 and 0.90 L h(-1), however the energy consumption increased significantly. The results indicated the technical feasibility of the electrochemical treatment as post-treatment for UASB reactors treating wastewaters from pulp and paper plants.     

Degradation of bisphenol A using electrochemical assistant Fe(II)-activated peroxydisulfate process

Degradation of bisphenol A(BPA) in aqueous solution using sulfate radicals was investigated using the Fe(II)-activated peroxydisulfate(PDS) process, electrochemical process, electrochemical process with 2.5 mmol/L Na2S2O8 without Fe(II), and electrochemical assistant Fe(II)-activated PDS process. It was found that the electrochemical assistant Fe(II)-activated PDS process performed best in the degradation of BPA.The variables considered to influence the degradation efficiency of BPA were the initial concentration of Fe2 t, the initial concentration of Na2S2O8, and the current density. More than 97% of the BPA removals were achieved within 120 min under the optimum operational condition.The degradation of BPA was accompanied by the formation of phenol, hydroquinone, and small-molecule compounds such as succinic acid. The electron transfer was the principal step in the oxidation of BPA.     

Partial stream digestion of residual municipal solid waste.

Anaerobic digestion of residual municipal solid waste (MSW) has become more important than the digestion of source separated biowaste. More than 52% of the capacity available in Europe was designed for digestion of residual municipal waste by the end of 2006, while this was only 13% in 1998. Partial digestion of residual waste organics, by which only a part of the organics is digested, has been implemented to reduce the need for dewatering and subsequent wastewater treatment. The digestate coming from part of the organics is immediately mixed with the non-digested organic fraction. This organic fraction is drier and still contains a lot of energy which can be used to dry the digestate during the aerobic composting of the mixture of digested and undigested organics. Such a MBT-plant has been operating for over a year whereby 2/3 of the organics (including sludge cake) are digested (25,000 t/year) and mixed after digestion with the remaining 1/3 of the organics. Biogas production averages 125.7 Nm2 per ton fed and contained 56.2% of methane. The mixture of digestate and non-digested organics is aerated in tunnels during 4 to 6 weeks. The stabilized end product is landfilled, meeting the stringent German standards for inert landfills. By using a dry fermentation able to produce a digestate at 35% solids, there is no need for dewatering the digestate so that no wastewater is produced.     

臭氧在饮用水处理中的应用

阐述臭氧在水处理中的氧化消毒机理,其强氧化性能破坏了有机物的分子结构,将一部分有机物彻底分解,同时将大分子有机物生成小分子有机物,改变了有机物性质,提高了其可生化性。介绍臭氧在水处理中的应用,如预氧化对微污染水中有机物、无机物、藻类及颗粒物的去除,以及对饮用水消毒杀菌。     

Artemia salina acute immobilization test: a possible tool for aquatic ecotoxicity assessment

Despite the fact that the marine crustacean Artemia salina is extensively used in ecotoxicology, there is still a lack of information about its sensitivity to commonly used chemicals. In the presented study, acute toxicity of 18 commonly used chemicals - including organic solvents, industrial chemicals, metals and inorganic compounds - to A. salina was evaluated. A. salina showed a range of sensitivities to tested chemicals. Regarding all of the investigated organics, phenolic compounds expressed the highest toxicity to A. salina. Nitrite and mercury were the most toxic inorganic substances applied in the study. On the other hand, dimethyl sulfoxide, nitrate and ammonium were the least toxic. The possibility to use A. salina for interspecies correlation was assessed by comparison of sensitivities of different organisms (bacteria, fish, crustacean) to organic compounds. Correlation between various species was observed, especially between A. salina and fish. Due to the strong relation between toxicity and the logarithm of the octanol/water partition coefficient logP(OW,) lipophilicity was found to be the main factor influencing toxicity of the chosen organic compounds. No significant correlation between toxicity to A. salina and physico-chemical parameters of metals was observed.