Eduard Rott

Abstract

Extremwetterereignisse und Folgeerscheinungen des Klimawandels wie z. B. Hitze- und Dürreperioden und Extremniederschläge machen es erforderlich, dass Städte ihre Resilienz steigern und sich an die neuen Bedingungen anpassen. Blau-grüne Infrastrukturen können hierzu beitragen und einen wichtigen Beitrag leisten. Gleichwohl ist absehbar, dass eine Umstellung der Wasserinfrastruktur von konventionellen grauen zu blau-grünen Systemen jedoch nur im Zuge einer großflächigen Neugestaltung ganzer Stadtquartiere möglich sein wird. Der vorliegenden Fachbeitrag stellt in diesem Zusammenhang das Konzept einer Regenwasserbewirtschaftung zur Dürrevorsorge im urbanen Raum vor und erläutert, in welchen Bereichen dieses konkret angewendet werden kann.

Abstract

The zeolite clinoptilolite (CLI) is known to be a very good ion exchanger, as it consists of a three-dimensional structure formed of AlO4− and SiO4 tetrahedral, which are connected by a common oxygen atom. The micropores formed by this structure (with free diameters in the range of 0.40 nm and 0.72 nm) are fine enough to allow cations and water molecules to enter and be exchanged. CLI is a suitable, inexpensive, and globally available material for removing ammonium from highly-concentrated wastewater and is proven to be selective in ammonium uptake and regeneration since no effect of the provenance of the ammonium (matrix-free NH4Cl solution or sludge water) could be found. However, regeneration of the clinoptilolite is necessary to recover the adsorbed ammonium for further use and restore its capability for ion exchange. Within this work, the method by which clinoptilolite, loaded with ammonium (q = 8.1–16.6 mg/g) from different sludge waters and ammonium chloride solution, can be regenerated to yield a stoichiometric ammonium sulfate solution (ASS), that could be used, e.g., as a fertilizer, was investigated. A regeneration solution containing Na2SO4 (0.25 n(Na2SO4)/n(NH4+ads)) with a varying NaOH ratio (0–2.14 n(NaOH)/n(NH4+ads)) was tested. To obtain a high ammonium concentration in the eluate, a large mass fraction ω of 284 g/kg of CLI in the regeneration solution was applied. The effects of different ammonium loads, different origins of the ammonium, and residual moisture on the necessary components of the regeneration solution, in which an ASS is obtained within a contact time of 10 min at 22 °C, were studied. A stoichiometric ASS from CLI loaded up to a maximum of 13.5 mg/g was obtained with a mixture of 0.25 n(Na2SO4)/n(NH4+ads) together with 0.8–1.0 n(NaOH)/n(NH4+ads) for dry CLI, and 0.75 n(NaOH)/n(NH4+ads) for CLI with residual moisture.

Abstract

Magnetic microparticles functionalized with tailored ZnFeZr oxyhydroxide adsorbent were used for the reversible sorption of orthophosphate and recalcitrant organo-phosphonates from wastewater. The loaded particles were harvested magnetically from water, regenerated in an alkaline solution and reused numerous times. The applicability of the technology to treat brackish water reverse osmosis concentrates was tested under controlled synthetic conditions by investigating the influence of typical metals (Ca2+, Pb2+, Cu2+) on the removal of common phosphonates (HEDP, NTMP, EDTMP), and vice versa. When present at equimolar concentrations, metal cations enhanced the adsorption of phosphonates and were co-adsorbed at pH 4.0–4.5 (with removals of 83–93% for Pb2+ and 53–73% for Cu2+), likely through ternary complex formation. In the absence of metals, at pH > pHPZC ∼7 (the material point of zero charge), a drop in adsorption efficiency was observed for orthophosphate and all phosphonates. Thus, at pH 7, an increased adsorbent dose (>0.1 g/L) was necessary to remove 1 mg/L NTMP-P in 30 min. The reusability and effluent polishing potential of the ZnFeZr particles was demonstrated in a pilot test with municipal wastewater throughout 55 adsorption/desorption cycles without any drop in performance. Consistent removal of the non-reactive phosphorus species to ultra-low concentrations (<0.05 mg/L Ptot) and complete orthophosphate elimination (<0.005 mg/L PO4-P) was maintained under optimal conditions.

Abstract

Sludge water (SW) arising from the dewatering of anaerobic digested sludge causes high back loads of ammonium, leading to high stress (inhibition of the activity of microorganisms by an oversupply of nitrogen compounds (substrate inhibition)) for wastewater treatment plants (WWTP). On the other hand, ammonium is a valuable resource to substitute ammonia from the energy intensive Haber-Bosch process for fertilizer production. Within this work, it was investigated to what extent and under which conditions Carpathian clinoptilolite powder (CCP 20) can be used to remove ammonium from SW and to recover it. Two different SW, originating from municipal WWTPs were investigated (SW1: c0 = 967 mg/L NH4-N, municipal wastewater; SW2: c0 = 718–927 mg/L NH4-N, large industrial wastewater share). The highest loading was achieved at 307 K with 16.1 mg/g (SW1) and 15.3 mg/g (SW2) at 295 K. Kinetic studies with different specific dosages (0.05 gCLI/mgNH4-N), temperatures (283–307 K) and pre-loaded CCP 20 (0–11.4 mg/g) were conducted. At a higher temperature a higher load was achieved. Already after 30 min contact time, regardless of the sludge water, a high load up to 7.15 mg/g at 307 K was reached, achieving equilibrium after 120 min. Pre-loaded sorbent could be further loaded with ammonium when it was recontacted with the SW.

Abstract

Phosphonates are widely used in various industries. It is desirable to remove them before discharging phosphonate-containing wastewater. This study describes a large number of batch experiments with adsorbents that are likely suitable for the removal of phosphonates. For this, adsorption isotherms for four different granular ferric hydroxide (GFH) adsorbents were determined at different pH values in order to identify the best performing material. Additionally, the influence of temperature was studied for this GFH. A maximum loading for nitrilotrimethylphosphonic acid (NTMP) was found to be ∼12 mg P/g with an initial concentration of 1 mg/L NTMP-P and a contact time of 7 days at room temperature. Then, the adsorption of six different phosphonates was investigated as a function of pH. It was shown that GFH could be used to remove all investigated phosphonates from water and, with an increasing pH, the adsorption capacity decreased for all six phosphonates. Finally, five adsorption–desorption cycles were carried out to check the suitability of the material for multiple re-use. Even after five cycles, the adsorption process still performed well.

Abstract

Phosphonates are widely used as antiscalants for softening processes in drinking water treatment. To prevent eutrophication and accumulation in the sediment, it is desirable to remove them from the membrane concentrate before they are discharged into receiving water bodies. This study describes batch experiments with synthetic solutions and real membrane concentrate, both in the presence of and absence of granular ferric hydroxide (GFH), to better understand the influence of ions on phosphonate and phosphate adsorption. To this end, experiments were conducted with six different phosphonates, using different molar Ca:phosphonate ratios. The calcium already contained in the GFH plays an essential role in the elimination process, as it can be re-dissolved, and, therefore, increase the molar Ca:phosphonate ratio. (Hydrogen-)carbonate ions had a competitive effect on the adsorption of phosphonates and phosphate, whereas the influence of sulfate and nitrate ions was negligible. Up to pH 8, the presence of CaII had a positive effect on adsorption, probably due to the formation of ternary complexes. At pH > 8, increased removal was observed, with either direct precipitation of Ca:phosphonate complexes or the presence of inorganic precipitates of calcium, magnesium, and phosphate serving as adsorbents for the phosphorus compounds. In addition, the presence of (hydrogen-)carbonate ions resulted in precipitation of CaCO3 and/or dolomite, which also acted as adsorbents for the phosphorus compounds.

Abstract

Ten times at intervals of 1–2 months, individual treatment stages of two wastewater treatment plants (WWTPs) were analyzed for the five quantitatively most widely used phosphonates. The total dissolved concentration of the investigated phosphonates in the influents was between 131 µg/L and 384 µg/L. The nitrogen-free phosphonates 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) and 1-hydroxyethylidene(1,1-diphosphonic acid) (HEDP) accounted for an average proportion of 83–85%. Diethylenetriaminepenta(methylene phosphonic acid) (DTPMP) contributed with 13–14%, whereas aminotris(methylphosphonic acid) (ATMP) (≤15 µg/L) and ethylenediaminetetra(methylene phosphonic acid) (EDTMP) (≤11 µg/L) contents detected in the WWTP influents were comparatively low. The application of new analytical methods allowed the quantification of phosphonates in the solid fraction of the WWTP influents for the first time. High loads of phosphonates were determined (223–2555 mg/kg), indicating that 20%–80% of the phosphonates are present in the adsorbed state. The removal of total dissolved phosphonate by secondary clarification was between 69.7% and 92.4% (medians: 90.7% and 87.7%). In both WWTPs, HEDP (medians: 89.2% and 86.4%) was slightly better eliminated than PBTC (medians: 87.2% and 82.5%). In the sand filtration stage of a WWTP, the average removal was not further improved. In contrast, an additional removal of dissolved phosphonates could be achieved by activated carbon treatment (median: 96.4%). The proportion of phosphonate-P in the dissolved unreactive phosphorus fraction was consistently between 10% and 40% throughout all treatment stages.

Abstract

Sediment, suspended matter (SM), and water of a large river (Neckar; River1) and a small river (Körsch; River2) were analyzed for the phosphonates 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), 1-hydroxyethylidene (1,1-diphosphonic acid) (HEDP), aminotris (methylphosphonic acid) (ATMP), ethylenediaminetetra (methylene phosphonic acid) (EDTMP), and diethylenetriaminepenta (methylene phosphonic acid) (DTPMP). Ten samplings were performed at intervals of one to two months during one year, each covering the relevant matrices before and behind the discharge point of a wastewater treatment plant (WWTP). In River1, the total concentration of dissolved phosphonate did not change significantly (2.4–5.8 µg/L before vs. 2.5–6.6 µg/L behind WWTP; p = 0.9360). In River2, it increased significantly from <0.1–1.6 µg/L to 19–39 µg/L (p < 0.0001). Based on the median, the total phosphonate load in River1 sediment increased 1.9-fold (6.7–29.4 mg/kg before vs. 17.8–53.5 mg/kg behind WWTP; p = 0.0033) and in River2 by a factor of eight (1.8–5.0 mg/kg before vs. 18.1–51.4 mg/kg behind WWTP; p < 0.0001). This indicates that phosphonates discharged by WWTPs adsorb onto solid particles and accumulate in the sediment. In the case of River2, the SM load could reach values of 1000–1710 mg/kg behind the WWTP, presumably due to the introduction of insufficiently retained activated sludge particles of >2000 mg/kg phosphonate loads. In general, the nitrogen-free phosphonates PBTC and HEDP were most predominant in both dissolved and adsorbed form, of which HEDP had the highest adsorption affinity.

Abstract

Phosphonates are increasingly used as water-softening agents in detergents, care products, and industrial processes. Despite poor biodegradability, high removal rates during wastewater treatment (WWT) have been observed, owing to strong adsorption affinity to activated sludge and mineral surfaces. Due to phosphonates representing challenging analytes, no method for the compound-specific quantification of phosphonates from solid samples has hitherto been published. In order to improve the data foundation on the environmental fate of phosphonates, an analytical method based on anion exchange chromatography and detection by electrospray ionization coupled to tandem mass spectrometry (IC-ESI-MS/MS) was developed, allowing the trace quantification of phosphonates from surface water (LOQs between 0.04 and 0.16 $\mu$g/L), wastewater (LOQs between 0.6 and 2.3 $\mu$g/L), sediment and suspended matter of rivers (LOQ <þinspace0.1 mg/kg), and suspended matter of wastewater (LOQ <þinspace1 mg/kg). Specificity and selectivity were enhanced by the implementation of isotope-labeled internal phosphonate standards derived through synthesis. This study describes the development of a comprehensive tool set for the determination of aminotris(methylenephosphonic acid) (ATMP), diethylenetriaminepenta(methylenephosphonic acid) (DTPMP), ethylenediaminetetra(methylenephosphonic acid) (EDTMP), 1-hydroxyethanediphosphonic acid (HEDP), and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) during WWT and in the aqueous environment. In the investigated matrices, HEDP and PBTC were generally present in highest and EDTMP in lowest abundance. The phosphonate contents detected in river water were in the sub to low $\mu$g/L range, depending on the wastewater burden, whereas contents in the low to medium $\mu$g/L range were found in untreated wastewater. The loads of the solid phases exceeded the contents of the corresponding liquid phases by roughly three orders of magnitude. Current data imply that phosphonates undergo significant partitioning to the solid phase during WWT and in natural water bodies.

Abstract

Effluent of a municipal wastewater treatment plant (WWTP) was treated on-site with the UV/chlorine (UV/HOCl) advanced oxidation process (AOP) using a pilot plant equipped with a medium pressure UV lamp with an adjustable performance of up to 1 kW. Results obtained from parallel experiments with the same pilot plant, where the state of the art UV/H2O2 AOP was applied, were compared regarding the removal of emerging contaminants (EC) and the formation of adsorbable organohalogens (AOX). Furthermore, the total estrogenic activity was measured in samples treated with the UV/chlorine AOP. At an energy consumption of 0.4 kWh/m3 (0.4 kW, 1 m3/h) and in a range of oxidant concentrations from 1 to 6 mg/L, the UV/chlorine AOP had a significantly higher EC removal yield than the UV/H2O2 AOP. With free available chlorine concentrations (FAC) in the UV chamber influent of at least 5 mg/L (11 mg/L of dosed Cl2), the total estrogenic activity could be reduced by at least 97%. To achieve a certain concentration of FAC in the UV chamber influent, double to triple the amount of dosed Cl2 was needed, resulting in AOX concentrations of up to 520 µag/L.

Abstract

This work investigates the influence of ammonium ions and the organic load (chemical oxygen demand (COD)) on the UV/chlorine AOP regarding the maintenance of free available chlorine (FAC) and elimination of 16 emerging contaminants (ECs) from wastewater treatment plant effluent (WWTE) at pilot scale (UV chamber at 0.4 kW). COD inhibited the FAC maintenance in the UV chamber influent at a ratio of 0.16 mg FAC per mg COD (kHOCl–COD = 182 M−1s−1). An increase in ammonium ion concentration led to a stoichiometric decrease of the FAC concentration in the UV chamber influent. Especially in cold seasons due to insufficient nitrification, the ammonium ion concentration in WWTE can become so high that it becomes impossible to achieve sufficiently high FAC concentrations in the UV chamber influent. For all ECs, the elimination effect by the UV/combined Cl2 AOP (UV/CC) was not significantly higher than that by sole UV treatment. Accordingly, the UV/chlorine AOP is very sensitive and loses its effectiveness drastically as soon as there is no FAC but only CC in the UV chamber influent. Therefore, within the electrical energy consumption range tested (0.13–1 kWh/m3), a stable EC elimination performance of the UV/chlorine AOP cannot be maintained throughout the year.

Abstract

This work proposes a technology for phosphonate removal from wastewater using magnetically separable microparticles modified with a tailored ZnFeZr-oxyhydroxide adsorbent material which proved to be highly efficient, reaching a maximum loading of ∼20 mg nitrilotrimethylphosphonic acid-P/g (215 μmol NTMP/g) at room temperature, pH 6 and 30 min contact time. The adsorption process at pH < 7 was fast, following the pseudo-second-order kinetics model. Furthermore, NTMP adsorption onto ZnFeZr-oxyhydroxide proved to be endothermic. At pH > pHpzc ≈7 (point of zero charge of the material) a drop in adsorption efficiency was observed for phosphate and for five different investigated phosphonates. Adsorption of NTMP could not be detected at pH > 8, however, the presence of more than 0.5 mM CaII improved significantly the adsorption efficiency. Successful reusability of the engineered particles was demonstrated throughout 30 loading cycles by changing the operational conditions (dose, pH) to optimize the performance. At optimal conditions, complete phosphonate removal was observed even after 30 cycles of particles’ reuse in a synthetic NTMP-solution and DTPMP-rich membrane concentrate. In each cycle, phosphorus was desorbed and concentrated in a 2 M NaOH. Industrial phosphonate-containing wastewaters rich in calcium, e.g. membrane concentrates, proved to be especially suitable for treatment with the particles.

Abstract

This paper introduces a procedure to investigate the adsorption of phosphonates onto iron-containing filter materials, particularly granular ferric hydroxide (GFH), with little effort and high reliability. The phosphonate, e.g., nitrilotrimethylphosphonic acid (NTMP), is brought into contact with the GFH in a rotator in a solution buffered by an organic acid (e.g., acetic acid) or Good buffer (e.g., 2-(N-morpholino)ethanesulfonic acid) MES and N-cyclohexyl-2-hydroxyl-3-aminopropanesulfonic acid CAPSO) in a concentration of 10 mM for a specific time in 50 mL centrifuge tubes. Subsequently, after membrane filtration (0.45 µm pore size), the total phosphorus (total P) concentration is measured using a specifically developed determination method (ISOmini). This method is a modification and simplification of the ISO 6878 method: a 4 mL sample is mixed with H2SO4 and K2S2O8 in a screw cap vial, heated to 148-150 °C for 1 h and then mixed with NaOH, ascorbic acid and acidified molybdate with antimony(III) (final volume of 10 mL) to produce a blue complex. The color intensity, which is linearly proportional to the phosphorus concentration, is measured spectrophotometrically (880 nm). It is demonstrated that the buffer concentration used has no significant effect on the adsorption of phosphonate between pH 4 and 12. The buffers, therefore, do not compete with the phosphonate for adsorption sites. Furthermore, the relatively high concentration of the buffer requires a higher dosage concentration of oxidizing agent (K2S2O8) for digestion than that specified in ISO 6878, which, together with the NaOH dosage, is matched to each buffer. Despite the simplification, the ISOmini method does not lose any of its accuracy compared to the standardized method.

Abstract

The worldwide increasing consumption of the phosphonates 2-phosphonobutane-1,2,4-tricarboxylic acid PBTC, 1-hydroxyethane 1,1-diphosphonic acid HEDP, nitrilotris(methylene phosphonic acid) NTMP, ethylenediamine tetra(methylene phosphonic acid) EDTMP and diethylenetriamine penta(methylene phosphonic acid) DTPMP over the past decades put phosphonates into focus of environmental scientists and agencies, as they are increasingly discussed in the context of various environmental problems. The hitherto difficult analysis of phosphonates contributed to the fact that very little is known about their concentrations and behavior in the environment. This work critically reviews the existing literature up to the year 2016 on the potential environmental relevance of phosphonates, their biotic and abiotic degradability, and their removal in wastewater treatment plants (WWTPs). Accordingly, despite their stability against biological degradation, phosphonates can be removed with relatively high efficiency (> 80%) in WWTPs operated with chemical phosphate precipitation. In the literature, however, to our knowledge, there is no information as to whether an enhanced biological phosphorus removal alone is sufficient for such high removal rates and whether the achievable phosphonate concentrations in effluents are sufficiently low to prevent eutrophication. It is currently expected that phosphonates, although being complexing agents, do not remobilize heavy metals from sediments in a significant amount since the phosphonate concentrations required for this (> 50 μg/L) are considerably higher than the concentrations determined in surface waters. Various publications also point out that phosphonates are harmless to a variety of aquatic organisms. Moreover, degradation products thereof such as N-(phosphonomethyl)glycine and aminomethylphosphonic acid are regarded as being particularly critical. Despite their high stability against biological degradation, phosphonates contribute to eutrophication due to abiotic degradation (mainly photolysis). Furthermore, the literature reports on the fact that phosphonates in high concentrations interfere with phosphate precipitation in WWTPs. Thus, it is recommended to remove phosphonates, in particular from industrial wastewaters, before discharging them into water bodies or WWTPs.

Abstract

The supply of food to the growing world population requires an increasing amount of nitrogen fertilizers, which can be achieved both by the energy-intensive Haber–Bosch process and by recovering ammonium from wastewater. Within the scope of this work, it is investigated to what extent different clinoptilolites (CLIs) can be used as ion-exchangers for the removal of ammonium from highly concentrated solutions. To this end, finely ground CLIs with different grain sizes (EcoZeo 20 and CCP 20: 0–20 µm, Micro 200: 0–200 µm) were tested for their sorption properties by varying the parameters of the sorption solution (c0 = 1000 mg NH4-N/L) such as pH, temperature, or contact time. All three CLIs tested were effective at adsorbing ammonium. In a pH range from 2 to 8, all CLIs were able to eliminate ammonium equally well. Furthermore, a contact time of 60 min was sufficient to achieve 84–88% of the maximum load. At a temperature of 34 °C, the highest loading was achieved (investigated range: 10–34 °C), indicating that the adsorption process of all CLIs was exergonic and endothermic. Especially for wastewater streams with high ammonium concentrations such as sludge water from wastewater treatment plants, CLI proved to be suitable to adsorb ammonium.

Abstract

Phosphonates are an important group of phosphorus-containing compounds due to their increasing industrial use and possible eutrophication potential. This study involves investigations into the methods UV/FeII, Fenton and UV/Fenton for their removal from a pure water matrix and industrial wastewaters. It could be shown that the degradability of phosphonates by UV/FeII (6 kWh/m3) in pure water crucially depended on the pH and was higher the less phosphonate groups a phosphonate contains. The UV/FeII method is recommended in particular for the treatment of concentrates with nitrogen-free phosphonates, only little turbidity and a low content of organic compounds. Using Fenton reagent, the degradation of polyphosphonates was relatively weak in a pure water matrix (<20% transformation to o-PO43–). By means of the Photo-Fenton method (6 kWh/m3), those phosphonates with the smallest numbers of phosphonate groups were easier degraded as well at pH 3.5 in a pure water matrix (o-PO43– formation rates of up to 80%). Despite an incomplete transformation of organically bound phosphorus to o-PO43– with Fenton reagent in an organically highly polluted wastewater (max. 15%), an almost total removal of the total P occurred. The most efficient total P elimination rates were achieved in accordance with the following Fenton implementation: reaction → sludge separation (acidic) → neutralization of the supernatant → sludge separation (neutral). Accordingly, a neutralization directly after the reaction phase led to a lower total P removal extent.

Abstract

Phosphonates are to be removed from industrial wastewater before they reach municipal wastewater treatment plants or surface waters. Industrial wastewaters contaminated with the phosphonates 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), 1-hydroxyethylidene-(1,1-diphosphonic acid) (HEDP), nitrilotrimethylphosphonic acid (NTMP), ethylenediamine tetra(methylene phosphonic acid) (EDTMP) and diethylenetriamine penta(methylene phosphonic acid) (DTPMP) can be subdivided into: (1) mostly clear concentrates with a high water hardness, and (2) organically polluted wastewaters, for instance from the paper and textile industries. Our own flocculation experiments with FeIII and AlIII salts showed that, at a pH of 7.5, the adsorption affinity of polyphosphonates onto iron hydroxides and aluminum hydroxides significantly decreases with an increasing number of C-P bonds (HEDP > NTMP > EDTMP > DTPMP). In comparison to pure water spiked with phosphonates, the total P removal from concentrates occurred at similar and even lower flocculant dosage concentrations (ß = 4–8) (ß is the molar ratio of dosed metal concentration to total P concentration in the raw sample). In organically polluted industrial wastewaters, the formation of flocks, and therefore the total P decrease, only occurred after exceeding a certain flocculant concentration, which varied strongly depending on the wastewater type (ß = 0.6–86). Below that concentration, the flocculant underwent complexation, and no elimination could be observed. For most of the wastewaters, the required ß values for at least 80% total P decrease were very similar for both FeIII and AlIII. Furthermore, Ca(OH)2 as flocculant turned out to be an effective tool for total P removal and simultaneous softening of calcareous concentrates.

Abstract

Discharge of toxic industrial wastewaters into biological wastewater treatment plants may result in inhibition of activated sludge bacteria (ASB). In order to find an appropriate method of detoxification, the wastewater of a pesticide-processing plant in Vietnam was treated with three different methods (FeIII, powdered activated carbon (PAC), Fenton (FeII/H2O2)) analyzing the detoxification effect with the nitrification inhibition test (NIT), respiration inhibition test (RIT) and luminescent bacteria test (LBT). The heterotrophic ASB were much more resistant to the wastewater than the autotrophic nitrificants. The NIT turned out to be more suitable than the RIT since the NIT was less time-consuming and more reliable. In addition, the marine Aliivibrio fischeri were more sensitive than the nitrificants indicating that a lack of inhibition in the very practical and time-efficient LBT correlates with a lack of nitrification inhibition. With 95%, the Fenton method showed the highest efficiency regarding the chemical oxygen demand (COD) removal. Although similar COD removal (60–65%) was found for both the FeIII and the PAC method, the inhibitory effect of the wastewater was reduced much more strongly with PAC. Both the NIT and the LBT showed that the PAC and Fenton methods led to a similar reduction in the inhibitory effect.

Abstract

Effluent of a municipal wastewater treatment plant was treated with UV/chlorine (UV/HOCl) advanced oxidation process (AOP) in technical scale on-site using a medium pressure UV lamp with an adjustable power of up to 1 kW (Siemens AG, Germany). Results, obtained from parallel experiments, where state of the art UV/H2O2 AOP was applied, were compared especially regarding the elimination of emerging contaminants (e.g. carbamazepine, diclofenac) and hygienic aspects (bacterial count). The total estrogenic activity was measured in samples, where UV/chlorine AOP was applied. By variation of oxidant dosage at constant UV radiation as well as constant oxidant dosage at variation of UV radiation several process settings were tested. Additional experiments examined the influence of the organic load (measured as COD) on the UV/chlorine AOP performance. It could be shown that the UV/chlorine AOP is more effective concerning the elimination of emerging contaminants and hygienic aspects compared to the UV/H2O2 AOP. The total estrogenic activity of wastewater treatment effluent could be reduced by the UV/chlorine AOP significantly.