This study reports the occurrence of eight bisphenols (BPs): bisphenol AF (BPAF), bisphenol AP (BPAP), bisphenol B (BPB), bisphenol C (BPC), bisphenol E (BPE), bisphenol F (BPF), bisphenol S (BPS) and bisphenol Z (BPZ) in wastewaters (WWs). Sample preparation involved pre-concentration with SPE cartridges (Oasis HLB), followed by derivatization using N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide with 1% tert-butyldimethylchlorosilane. Chemical analysis was based on gas chromatography-mass spectrometry. A validated method with limits of detection (LODs) at ngL range was applied to WWs collected at five Slovene wastewater treatment plants (WWTPs) and WW inflows from industrial, commercial and residential sources entering the sewerage systems of two catchments (Domžale-Kamnik (DK) and Ljubljana (LJ)). The presence of all BPs was confirmed in three inflows in DK and two inflows in the LJ catchments. High cumulative concentrations of all BPs were determined in WW from food processing facilities (LJ: 3030ngL and DK: 599ngL). A high detection frequency was observed in the WW from two textile cleaning companies (6 BPs for LJ and 8 BPs for DK). The analysis of WW from WWTPs revealed that only BPF (36.7ngL) and BPS (40.6ngL) were >LODs in the influents, whereas other BPs were detected also in the effluents. BPZ was found in the highest concentration (403ngL at WWTP-DK). WW collected at this WWTP also contained the highest amount of BPE (238ngL). Although BPs removal could not be directly compared between the WWTPs, with the exception of BPAP and BPB in the case of two smaller WWTPs (6.39%-43.2%) bisphenols were in general highly removed (≥96.2%). Finally, levels of BPC>LOD are reported for first time (WWTP in the DK catchment: 1.01ngL-11.8ngL; LJ inflow from food processing plant up to 2560ngL).

In the paper three linear aeration controllers that can be easily implemented are presented and evaluated on the activated sludge process pilot plant. Controllers differ according to the information that is used about the process, which can be oxygen in the last aerobic reactor, ammonia in the last aerobic reactor and ammonia in the influent. The aeration controllers that are addressed are: oxygen cascade PI controller, ammonia cascade PI controller and ammonia feedforward-cascade PI controller. Experiments show that, in comparison with the oxygen cascade PI controller, the ammonia cascade PI controller allows better control of effluent ammonia and airflow savings of around 23%, while the ammonia feedforward-cascade PI controller gives the best reduction of ammonia peaks and can save up to 45% of the airflow.

Two different types of carriers differing fundamentally in size, shape and structure were evaluated in parallel testing for nitrification potential using the moving-bed biofilm reactor (MBBR) technology. One of the carriers used was a cylindrical high-density polyethylene ring shaped carrier (AnoxKaldnes, K1 carrier) and the other was a spherical polyvinyl alcohol (PVA) gel bead shaped carrier (Kuraray, PVA-gel carrier). For each MBBR process, using artificial wastewater under autotrophic conditions, high maximal nitrification rates at 20 degrees C were obtained. For the K1 carrier up to 27 mgNH(4)-N/L.h (at 37% filling fraction) was found, corresponding to 49 mgNH(4)-N/L.h at the recommended maximum filling fraction of 67%. This corresponds to a nitrification area rate of 3.5 gNH(4)-N/m(2).d for the K1 carrier at 20 degrees C. For the PVA-gel carrier up to 32 mgNH(4)-N/L.h (at 9.6% filling fraction) was found, corresponding to 50.0 mg NH(4)-N/L.h at the recommended maximum filling fraction of 15%. At the recommended filling fractions, the two carriers therefore required about the same reactor volume to reach the maximum observed nitrification rate. This presumption allowed us to estimate the effective specific surface area for the PVA gel carrier up to 2,500 m(2)/m(3) versus 1,000 m(2)/m(3) when only the outer surface is considered.

Mathematical models and simulation are becoming increasingly used tools in the optimization of wastewater treatment plants. In this paper, the use of these tools is presented for wastewater treatment plant upgrading. Two case studies are presented, which will be upgraded for tertiary treatment to achieve effluent total nitrogen and total phosphorous concentrations below 10 mg/l and 1 mg/l, respectively. The plant performance after upgrading was assessed by first designing the process model, before upgrading the model for future operation under dynamic influent conditions. Long-term simulations revealed some bottlenecks in the upgraded plant performance and thus helped to improve the plant designs. In one case the total volume of the reactors was increased subsequently, while in the other case tighter denitrification control or additional reject water treatment was proposed. These results indicate that mathematical models can be considered as valuable tools to complement the established wastewater treatment plant design procedures. Advantages are gained by simulating the operation under dynamic operating conditions, precise wastewater characterization, as well as adjustment of stoichiometric and kinetic parameters to a particular wastewater treatment plant operation.

A pilot-plant study was conducted to evaluate the performance of a moving-bed biofilm reactor process using PVA-gel beads as a biocarrier. Real primary-settled wastewater was fed to the pre-denitrification system and removals of nitrogenous and organic contaminants were evaluated over a 1-year period. The results demonstrated that at a total nitrogen (TN) loading of 18 mg/L.h, a TN removal efficiency in keeping with and even exceeding the theoretical maximum efficiency based on the level of internal recycle, was possible and a nitrification rate of 15 mg/L.h was sustained with a HRT of only 2.5 h at 15 degrees C. Furthermore, soluble COD and BOD5 in the effluent of the pilot plant were reduced to levels well below most regulatory discharge limits. In addition, the possibility of using this biocarrier in a system, including the elimination of waste organic sludge, was discussed.