An overview of the integration of ozone systems in biological treatment steps.

Despite the well-known potential and performance of combined biological and ozonation processes for wastewater treatment, only few full-scale applications are published. Beside the synergistic effects of such process combination, which lead to oxidation of recalcitrant and inhibitory compounds or intermediates by enhancement of their biodegradability, the key for raising applicability is the improvement of the ozonation efficiency. An overview about the history and progress of full-scale applications, which deals with combined ozonation and biological treatment is given. Recently more than 40 applications exist, but many of them are not published. Therefore, a couple of selected not yet published applications have been mentioned in this paper. Landfill leachate and industrial wastewater treatment were mostly applicated, while treatment of municial wastewater treatment plant (WWTP) effluents are of increasing interest due to several advantages such as disinfection, decolourisation and removal of persistent dissolved organic carbon (DOC) for water re-use and groundwater recharge.     

催化湿式氧化高浓度SDBS废水的研究

以过渡金属氧化物CuO为主活性组分,通过复合第二活性组分Co3O4和掺入电子助剂CeO2的考察,研制出适用于催化湿式氧化处理高浓度十二烷基苯磺酸钠(SDBS)废水的复合催化剂。实验结果表明,新制备的复合催化剂有较好的催化活性。通过对反应温度、氧气分压和废水pH值等工艺条件的考察,得出催化湿式氧化处理高浓度SDBS废水适宜的工艺条件为:反应温度为280℃、氧气分压为3 MPa、pH值为8.2,在此条件下用自制的催化剂处理初始COD质量浓度为4 942.1 mg/L的SDBS废水,在120 min内,COD去除率达到88.1%,而在相同条件下未加催化剂的湿式氧化COD去除率只有30.7%。     

Comparison of activated sludge microbial communities using Biolog™ MicroPlates

Laboratory models of wastewater treatment plants (WWTP) provide controlled systems for studying chemical biodegradability and removal as well as WWTP microbial ecology and engineering. In this study, Continuous Activated Sludge (CAS, 3-L) and Semi-Continuous Activated Sludge (SCAS, 2.5-L) units were maintained for up to 17 weeks using feedstocks of either fresh WWTP sewage, a complex synthetic wastewater, or a simple glucose/peptone feed (SCAS only). The goal of this research was to evaluate the microbial communities of the WWTP and the CAS and SCAS units to determine which laboratory models, and which feedstocks, were able to maintain the complexity of the WWTP microbial communities in the laboratory. One endpoint evaluated to this study was microbial community metabolic profiles, as measured using Biolog MicroPlates. Biolog Microplates contain 95 different pre-dried carbon sources and a tetrazolium dye used to spectrophotometrically measure oxidation of carbon sources. The Biolog carbon source utilization patterns of the CAS communities were similar to the SCAS communities when both were fed WWTP sewage. In addition, the profiles for these laboratory models remained similar to the WWTP microbial communities, even over an extended cultivation time (l6 weeks) in the CAS systems. Amendment with a complex synthetic wastewater (25% by chemical oxygen demand) did not affect microbial metabolic response in the CAS systems, but amendment (100% by chemical oxygen demand) with a simple glucosepeptone wastewater in the SCAS system resulted m a measurable shift in microbial metabolic response.     

An integrated approach for improving the wastewater discharge and treatment systems

Since treatment plants have been built all over Germany during the last decades, the water quality of receiving streams has been improved remarkably. But there are still a lot of quality problems left, which are caused e.g. by combined sewer overflows (CSO), treatment plant effluents or rainwater discharges from separate sewer systems. At present different efforts are undertaken to control sewer systems in order to improve the operation of urban drainage systems or more generally, design processes. The Emschergenossenschaft and Lippeverband (EG/LV) are carrying out research studies, which are focusing on a minimization of total emissions from sewer systems both from wastewater treatment plant (WWTP) effluents and from CSO. They consider dynamic interactions between rainfall, resultant wastewater, combined sewers, WWTP and receiving streams. Therefore, in an advanced wastewater treatment, a model-based improvement of WWTP operation becomes more and more essential, and consequently a highly qualified operational staff is needed. Some aspects of the current research studies are presented in this report. The need and the use of an integrated approach to combine existing model components in order to optimize dynamic management of combined sewer systems (CSS) with a benefit for nature are outlined.     

Photo-Fenton processes assisted by solar light used as preliminary step to biological treatment applied to winery wastewaters.

Winery wastewaters are difficult to treat by conventional biological processes, because they are seasonal and experience substantial flow variations. Photocatalytic advanced oxidation is a promising technology for wastewaters containing high amounts of organic matter. In this research work, solar assisted photo-Fenton processes of both heterogeneous and homogeneous phase are used in the pre-treatment of winery wastewaters. The results of these experiments have confirmed the suitability of the photo-Fenton processes, due to these treatments achieving purification levels of up to 50% (measured as total organic carbon). The intermediate effluents are treated adequately by aerobic biological treatment (activated sludge process), due to the decrease in organic matter concentration present in winery wastewaters. The possibility of a combined photo-Fenton process, based on the use of sunlight, and aerobic biological treatment (activated sludge) is suggested.     

Activated sludge wastewater treatment plants optimisation to face pollution overloads during grape harvest periods.

The principal objective of our study was to optimise a municipal activated sludge wastewater treatment plant (WWTP) to face high organic flows due to viticulture effluents inputs. Treatment file optimization consisted in testing different treatment lines, changing the number and volume of biological basins and clarifiers, with or without a buffer basin upstream, with a view to achieving a better reduction of COD. The actual WWTP biological stage is composed of two aerated basins whose total volume is 1365 m3. The studied cases are successively, the installation of a single basin of 1365 m3, then of several basins whose total volume remains constant and equal to 1365 m3. Another case was also considered, that of an aerated basin followed by a first clarifier and then, by another aerated basin and a second clarifier. All scenarios presented below were evaluated, for standard dry weather conditions and for high organic load conditions, as encountered during the grape harvest period. The method used was to carry out various simulations, using numerical modelling, and to compare the impact of different process line scenarios and management strategies on the activated sludge WWTP efficiencies.     

Analysing sludge balance in activated sludge systems with a novel mass transport model

In activated sludge systems the mechanically treated wastewater is biologically cleaned by biomass (activated sludge). The basic requirement of an efficient biological wastewater treatment is to have as a high biomass concentration in the biological reactor (BR) as possible. The activated sludge balance in activated sludge systems is controlled by the settling, thickening, scraper mechanism in the secondary settling tank (SST) and sludge returning. These processes aim at keeping maximum sludge mass in the BR and minimum sludge mass in the SST even in peak flow events (storm water flow). It can be, however, only reached by a high SST performance. The main physical processes and boundary conditions such as inhomogeneous turbulent flow, geometrical features of the SST, wastewater treatment plant (WWTP) load, return sludge flow, sludge volume index etc. all influence settling thickening and sludge returning. In the paper a novel mass transport model of an activated sludge system is presented which involves a 2-dimensional SST model coupled with a mixed reactor model of the biological reactor. It makes possible to investigate different sludge returning strategies and their influence on the sludge balance of the investigated activated sludge system, furthermore, the processes determining the flow and concentration patterns in the SST. The paper gives an overview on the first promising model results of a prevailing peak flow event investigation at the WWTP of Graz.     

Simultaneous determination of several veterinary pharmaceuticals in effluents from urban, livestock and slaughterhouse wastewater treatment plants using a simple chromatographic method

Minocycline, oxytetracycline, tetracycline, enrofloxacin and ceftiofur, commonly used veterinary pharmaceuticals, were searched in four urban, two livestock and two slaughterhouse effluents from wastewater treatment plants (WWTPs) in the north of Portugal. A simple method that includes solid-phase extraction followed with analysis by high-performance liquid chromatography with diode array detector was established and applied to the simultaneous determination of the five pharmaceuticals in WWTP effluents. This method, which is expeditious, inexpensive and available in most laboratories, showed to be useful for screening for problematic levels of drugs in WWTP effluents. It is known that several livestock and slaughterhouse effluents (pre-treated or treated) are discharged to the urban network before discharge into the environment. The presence of these drugs in such effluents can constitute a significant environmental problem that should be addressed, by the monitoring of these drugs and by implementation of methodologies that contribute to their decrease/elimination from wastewaters. Minocycline (≤6 μg L(-1)), oxytetracycline (≤7 μg L(-1)), tetracycline (≤6 μg L(-1)) and enrofloxacin (<2 μg L(-1)) could be detected and/or quantified in three urban effluents. Detectable levels of enrofloxacin (<2 μg L(-1)) and quantifiable levels of tetracycline (≤15 μg L(-1)) were found in the slaughterhouse effluents.     

Reuse potential analysis on WWTP effluent of industrial parks in Taiwan.

This study examined the reuse potential of the effluents discharged from several unified wastewater treatment plants (WWTPs) of industrial parks in Taiwan, with designed capacity exceeding 10,000 CMD. Parameters were selected based on the relevant reuse purposes. The "potential recycling percentage", R of the WWTP effluent was defined as the maximal percentage of pure water extractable by the "ideal reverse osmosis module" while the RO retentate still met local effluent standards and required no treatment. The analytical results demonstrated that the WWTP effluents had potential for recycling. A pilot plant was installed in one of the WWTPs. The treatment process included a sand filter, an ultrafiltration unit (UF) and a reverse osmosis module (RO). Results of this study demonstrated that the production quantity and quality are stable and appropriate for various purposes, including both industrial and domestic applications.     

Modeling the fate and transport of organic and nitrogen species in soil aquifer treatment process.

Soil aquifer treatment (SAT) is a promising technique for wastewater reclamation and reuse. This treatment strategy takes advantage of physicochemical and biological processes in the subsurface. The model employed in this study is based on MODFLOW-SURFACT (HydroGeoLogic, Inc.), a three-dimensional model for variably saturated flow and reactive mass transport. The model accounts for reactions including the nitrification of ammonium, the denitrification of nitrate, and the oxidation of organic carbon. Concentration of dissolved oxygen and biomasses involved in aerobic and anaerobic biological reactions forms the basis for estimates of nonlinear reaction rates formulated using a multiple-Monod expression. Illustrative simulations were conducted in a two-dimensional cross-sectional domain, with unsaturated and saturated zones. They examine the effects that site and operational conditions have on the performance of a SAT system. The parameters and conditions of concern included length of the wet/dry cycle, ground surface condition, and infiltration rate. From the simulations, we found that organic carbon was effectively removed in all cases. The availability of oxygen was a key factor in predicting the production and removal of nitrate. Overall, the model successfully described the fate and transport of the key constituents during the wet/dry operational periods in both unsaturated and saturated subsurface.     

Analysis and fate of insect repellents.

During summer months the insect repellent N,N-diethyl-m-toluamide (DEET) could always be detected in influents and effluents of wastewater treatment plants (WWTP) and anthropogenically influenced surface waters. In Germany the concentrations have decreased constantly since 1999, when DEET was substituted by Bayrepel. DEET can be degraded in WWTP, but only after an adaptation period and values in the influent above the threshold value. Since the year 2000 Bayrepel could also be detected during the summer months in the influents of WWTP, whereas in the effluents Bayrepel was not present.     

Determination and occurrence of organic micropollutants in reverse osmosis treatment for advanced water reuse

The growing demand on water resources has increased the interest in wastewater reclamation for multiple end-use applications such as indirect and direct potable reuse. In these applications, the removal of organic micropollutants is of a greater concern than in conventional wastewater treatment. This article presents a collection of data of trace organic micropollutants in an urban wastewater treatment plant (WWTP) in North East Spain using reverse osmosis (RO) membrane treatment. The RO rejection values of the organic molecules studied with a wide range of solute size and hydrophobicity were determined. Several chromatographic methods monitoring different endocrine disrupting chemicals (EDCs), pharmaceuticals and personal care products (PPCPs) were used. Results indicated that secondary effluents from this Spanish WWTP contained most of the studied organic compounds indicating incomplete removal of organics in the conventional treatment of the plant. However, the rejection of most micropollutants was high for all three RO membrane types (low energy, high rejection, fouling resistant) tested. It was observed that some selected micropollutants were less efficiently removed (e.g. the small and polar and the more hydrophobic) and the molecular weight and membrane material influenced removal efficiencies.     

Membrane filtration and sonication for industrial wastewater reuse

This paper presents an experimental study aimed at estimating the efficiency of the innovative process of ultrafiltration (UF) combined with sonication (Son.) for the refinement of treated effluent to be reused in wet textile processes. Such a novel approach, which has not yet been employed on a full industrial scale, has been experienced at pilot scale on the secondary effluent of the Baciacavallo wastewater treatment plant (WWTP), which treats part of the effluent from one of the largest textile industry districts in Italy. The combined treatment efficiency was assessed both on ozonated and non-ozonated Baciacavallo secondary effluent. The membrane filtration process was optimized in terms of running time, backwash, chemical addition and cleaning procedures. The sonication treatment was optimized on laboratory-scale with synthetic solutions (demineralized water added with dyestuffs) in terms of hydroxyl radicals formation rate, frequency, acoustic power, hydrogen peroxide addition, contact time and pH. The optimal conditions have been applied on the pilot-scale sonicator which was used in combination with the UF treatment. According to the experimental results, the best configuration within the Baciacavallo WWTP was the sonication of non-ozonated wastewater followed by the UF. The combined treatment guaranteed the compliance with the target values for wastewater reuse in wet textile industries. This study is part of the Research Project PURIFAST (Purification of industrial and mixed wastewater by combined membrane filtration and sonochemical technologies) LIFE + ENV/IT/000439.     

Catalytic oxidation with Al-Ce-Fe-PILC as a post-treatment system for coffee wet processing wastewater

The effluent from the anaerobic biological treatment of coffee wet processing wastewater (CWPW) contains a non-biodegradable compound that must be treated before it is discharged into a water source. In this paper, the wet hydrogen peroxide catalytic oxidation (WHPCO) process using Al-Ce-Fe-PILC catalysts was researched as a post-treatment system for CWPW and tested in a semi-batch reactor at atmospheric pressure and 25 °C. The Al-Ce-Fe-PILC achieved a high conversion rate of total phenolic compounds (70%) and mineralization to CO(2) (50%) after 5 h reaction time. The chemical oxygen demand (COD) of coffee processing wastewater after wet hydrogen peroxide catalytic oxidation was reduced in 66%. The combination of the two treatment methods, biological (developed by Cenicafé) and catalytic oxidation with Al-Ce-Fe-PILC, achieved a 97% reduction of COD in CWPW. Therefore, the WHPCO using Al-Ce-Fe-PILC catalysts is a viable alternative for the post-treatment of coffee processing wastewater.     

Advanced treatment of benzothiazole contaminated waters: comparison of O3, AC, and O3/AC processes.

Benzothiazole (BT) is a toxic and poorly biodegradable contaminant, usually found in wastewater from rubber related applications. This compound could be effectively eliminated using advanced treatment processes. This paper compares experimental results on detoxification systems based on ozone oxidation, activated carbon adsorption, and simultaneous adsorption-oxidation using ozone in the presence of activated carbon. The effect of pH (2-11), and the presence of radical scavengers (tert-butyl alcohol and sodium carbonate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with activated carbon adsorption increases the overall BT oxidation rate with respect to the ozonation process and activated carbon adsorption. In the presence of free radical scavenger, only a 44% reduction in BT removal rate is observed in the simultaneous treatment, as compared with 72% when ozonation treatment is used, suggesting that BT oxidation reactions mainly take place on the activated carbon surface.     

Water reuse for urban landscape irrigation: aspersion and health related regulations.

The Mediterranean seaside resort of Le Grau du Roi includes 40 hectares of landscaped areas spray irrigated with river water supplied through a separate network. Wastewater collected from several municipalities is treated in an activated sludge wastewater treatment plant (WWTP) and polished in waste stabilization ponds (WSPs). Planned substitution of treated wastewater for river water is hindered by spray irrigation prohibition within a 100 m distance from houses and recreational areas. WWTP and WSP effluents were monitored for pathogens with a particular attention to Legionella in Spring and Summer 2006. Helminth eggs, salmonellae and enteroviruses were never detected neither in WWTP effluent nor in the ponds. Legionella spp content was slightly higher or of the order of magnitude of river water contents. Regarding Legionella pneumophila contents, WSP effluent did not significantly differ from the river water. E.coli and enterococci contents in WSP effluents complied with the "excellent quality" criteria of the European Directive for coastal bathing waters. Therefore, substituting WSP effluents to river water is unlikely to alter health risks related to spray irrigation and, in this case, the buffer zone required by the French water reuse guidelines appears being short of support.     

Nitrogen speciation in wastewater treatment plant influents and effluents-the US and Polish case studies.

The fate of N species, particularly dissolved organic nitrogen (DON), through process trains of a wastewater treatment plant (WWTP) was investigated. In this study, three fully nitrifying plants in Illinois, USA and biological nutrient removal (BNR) plants in northern Poland were sampled for N characterization in the primary and secondary effluents as a function of the particle size distribution. The correlations between dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations were examined. The key findings are that DON becomes significant portion (about 20%) of the effluent N, reaching up to 50% of effluent total N in one of the Polish plants. The DON constituted 56-95% of total ON (TON) in the secondary effluents, whereas in the Polish plants the DON contribution was substantially lower (19-62%) and in one case (Gdansk WWTP) colloidal ON was the dominating fraction (62% of TON). The DOC to DON ratio in the US plants is significantly lower than that in the receiving waters indicating potential for deterioration of receiving water quality. In Polish plants, the influent and effluent C:N ratios are similar, but not in the US plants.     

Comparing cost and process performance of activated sludge (AS) and biological aerated filters (BAF) over ten years of full sale operation.

In the early 1990s, the Wastewater Treatment Plant (WWTP) of Frederikshavn, Denmark, was extended to meet new requirements for nutrient removal (8 mg/L TN, 1.5 mg TP/L) as well as to increase its average daily flow to 16,500 m(3)/d (4.5 MGD). As the most economical upgrade of the existing activated sludge (AS) plant, a parallel biological aerated filter (BAF) was selected, and started up in 1995. Running two full scale processes in parallel for over ten years on the same wastewater and treatment objectives enabled a direct comparison in relation to operating performance, costs and experience. Common pretreatment consists of screening, an aerated grit and grease removal and three primary settlers with chemical addition. The effluent is then pumped to the two parallel biological treatment stages, AS with recirculation and an upflow BAF with floating media. The wastewater is a mixture of industrial and domestic wastewater, with a dominant discharge of fish processing effluent which can amount to 50% of the flow. The maximum hydraulic load on the pretreatment section as a whole is 1,530 m(3)/h. Approximately 60% of the sewer system is combined with a total of 32 overflow structures. To avoid the direct discharge of combined sewer overflows into the receiving waters, the total hydraulic wet weather capacity of the plant is increased to 4,330 m(3)/h, or 6 times average flow. During rain, some of the raw sewage can be directed through a stormwater bypass to the BAF, which can be modified in its operation to accommodate various treatment needs: either using simultaneous nitrification/denitrification in all filters with recirculation introducing bottom aeration with full nitrification in some filters for storm treatment and/or post-denitrification in one filter. After treatment, the wastewater is discharged to the Baltic Sea through a 500 m outfall. The BAF backwash sludge, approximately 1,900 m(3) per 24 h in dry weather, is redirected to the AS plant. Primary settler sludge and the combined biosolids from the AS plant are anaerobically digested, with methane gas being used for generation of heat and power. On-line measurements for the parameters NO3, NO2, NH4, temperature as well as dissolved oxygen (DO) are used for control of aeration and external carbon source (methanol). Dosing of flocculants for P-removal is carried out based on laboratory analysis and jar tests. This paper discusses the experience gained from the plant operation during the last ten years, compiling comparative performance and cost data of the two processes, as well as their optimisation.     

Emissions of perfluorinated alkylated substances (PFAS) from point sources--identification of relevant branches

Effluents of wastewater treatment plants are relevant point sources for the emission of hazardous xenobiotic substances to the aquatic environment. One group of substances, which recently entered scientific and political discussions, is the group of the perfluorinated alkylated substances (PFAS). The most studied compounds from this group are perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS), which are the most important degradation products of PFAS. These two substances are known to be persistent, bioaccumulative and toxic (PBT). In the present study, eleven PFAS were investigated in effluents of municipal wastewater treatment plants (WWTP) and in industrial wastewaters. PFOS and PFOA proved to be the dominant compounds in all sampled wastewaters. Concentrations of up to 340 ng/L of PFOS and up to 220 ng/L of PFOA were observed. Besides these two compounds, perfluorohexanoic acid (PFHxA) was also present in nearly all effluents and maximum concentrations of up to 280 ng/L were measured. Only N-ethylperfluorooctane sulphonamide (N-EtPFOSA) and its degradation/metabolisation product perfluorooctane sulphonamide (PFOSA) were either detected below the limit of quantification or were not even detected at all. Beside the effluents of the municipal WWTPs, nine industrial wastewaters from six different industrial branches were also investigated. Significantly, the highest emissions or PFOS were observed from metal industry whereas paper industry showed the highest PFOA emission. Several PFAS, especially perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorododecanoic acid (PFDoA) and PFOS are predominantly emitted from industrial sources, with concentrations being a factor of 10 higher than those observed in the municipal WWTP effluents. Perfluorodecane sulphonate (PFDS), N-Et-PFOSA and PFOSA were not detected in any of the sampled industrial point sources.     

Membrane bio-reactor for textile wastewater treatment plant upgrading.

Textile industries carry out several fiber treatments using variable quantities of water, from five to forty times the fiber weight, and consequently generate large volumes of wastewater to be disposed of. Membrane Bio-reactors (MBRs) combine membrane technology with biological reactors for the treatment of wastewater: micro or ultrafiltration membranes are used for solid-liquid separation replacing the secondary settling of the traditional activated sludge system. This paper deals with the possibility of realizing a new section of one existing WWTP (activated sludge + clariflocculation + ozonation) for the treatment of treating textile wastewater to be recycled, equipped with an MBR (76 l/s as design capacity) and running in parallel with the existing one. During a 4-month experimental period, a pilot-scale MBR proved to be very effective for wastewater reclamation. On average, removal efficiency of the pilot plant (93% for COD, and over 99% for total suspended solids) was higher than the WWTP ones. Color was removed as in the WWTP. Anionic surfactants removal of pilot plant was lower than that of the WWTP (90.5 and 93.2% respectively), while the BiAS removal was higher in the pilot plant (98.2 vs. 97.1). At the end cost analysis of the proposed upgrade is reported.