Ralf Minke

Removal of Emerging Contaminants and Estrogenic Activity from Wastewater Treatment Plant Effluent with UV/Chlorine and UV/H2O2 Advanced Oxidation Treatment at Pilot Scale

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 µg/L.

Optimized Procedure for Determining the Adsorption of Phosphonates onto Granular Ferric Hydroxide using a Miniaturized Phosphorus Determination Method

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.

Influence of Ammonium Ions, Organic Load and Flow Rate on the UV/Chlorine AOP Applied to Effluent of a Wastewater Treatment Plant at Pilot Scale

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.

Impact of new sanitation technologies upon conventional wastewater infrastructures

Abstract Separation of wastewater split streams and utilization of the resources contained therein are an important prerequisite for a sustainable wastewater treatment. In areas with existing infrastructures, this leads to transition states during which current systems must continue to operate. A simple mass-flow based method was developed to assess the impacts of an incremental transition (co-digestion of blackwater and sewage sludge) upon plant operation. The results proved that blackwater co-digestion could be easily integrated into existing wastewater infrastructures; however, beyond 8% transition thickening was required due to hydraulic limitations in the digester. Additionally, nitrogen recovery was necessary beyond 35% transition to avoid unfavorable C:N ratios. The investigated concept also led to a power gain of 11 kWh/(PE∙a) due to enhanced biogas production and aeration savings. The developed Excel-based method was considered suitable for evaluating the benefits and probable tipping points for plant operation during transition to source-separated sanitation systems.