Pilot-scale hydrolysis of primary sludge for production of easily degradable carbon to treat biological wastewater or produce biogas.

Organic compounds in wastewater are required for the biological removal of nitrogen, but they can also be used for biogas production. Distribution of the internal organic carbon at the plant is therefore critical to ensure high quality of the treated water, reduce greenhouse gas emissions, and optimize biogas production. We describe a wastewater treatment plant designed to focus equally on energy production, water quality, and reduced emissions of greenhouse gases. A disk filter was installed to remove as much carbon as possible during primary treatment. Primary sludge was then hydrolyzed and centrifuged. The hydrolysate centrate contained volatile fatty acids and was used either for the secondary wastewater treatment or to produce biogas. The yield during hydrolysis was 30-35 g volatile fatty acid per kg dry material or 40-65 g soluble COD per kg total solid. The specific denitrification rate was 20-40 g/(g·min), which is on the same order of magnitude as that for commonly used external carbon sources. Hydrolysis at around 35 °C and pH 7 gave the best results. The hydrolysate centrate can be stored and added to the biological treatment to improve water quality and reduce emissions of nitrous oxide or it can be used to produce biogas to optimize the operation of the plant.

Municipal wastewater treatment targeting pharmaceuticals by a pilot-scale hybrid attached biofilm and activated sludge system (Hybas™).

A hybrid wastewater treatment process with combined attached biofilm (moving bed biofilm reactor) and activated sludge, named as Hybas™, was implemented for the treatment of municipal wastewater. The system consisted of six staged reactors in series including pre-denitrification and nitrification in the Hybas™ line and post-denitrification in a pure MBBR. In addition to the significant removal of nutrients and organic matter from municipal wastewater, Hybas™ also showed removal capacity for pharmaceuticals. Of particular interest was the enhanced removal for pharmaceuticals (i.e. X-ray contrast media) compared to other biological systems. Spiking experiments showed that the maximum removal rate constants (k, h-1) for 10 out of the 21 investigated pharmaceuticals (including diclofenac) were observed to occur within the two aerobic Hybas ™ reactors, operated in a flow-shifting mode that allows even biofilm growth of nitrifying bacteria. In total, 14 out of the 21 pharmaceuticals were removed by more than 50% during continuous flow operation in the all Hybas™ line and post-denitrification MBBR. The calculated and estimated removal contributions of pharmaceuticals by each individual reactor were also assessed.

Biological removal of pharmaceuticals from hospital wastewater in a pilot-scale staged moving bed biofilm reactor (MBBR) utilising nitrifying and denitrifying processes.

Hospital wastewater contains high concentrations of pharmaceuticals, which pose risks to receiving waters. In this study, a pilot plant consisting of six moving bed biofilm reactors (MBBRs) in series (with the intention to integrate Biological Oxygen Demand (BOD) removal, nitrification and denitrification as well as prepolishing Chemical Oxygen Demand (COD) for ozonation) was built to integrate pharmaceutical removal and intermittent feeding of the latter reactors aimed for micropollutant removal. Based on the experimental resultss, nitrifying MBBRs achieved higher removal as compared to denitrifying MBBRs except for azithromycin, clarithromycin, diatrizoic acid, propranolol and trimethoprim. In the batch experiments, nitrifying MBBRs showed the ability to remove most of the analysed pharmaceuticals, with degradation rate constants ranging from 5.0 × 10-3 h-1 to 2.6 h-1. In general, the highest degradation rate constants were observed in the nitrifying MBBRs while the latter MBBRs showed lower degradation rate constant. However, when the degradation rate constants were normalised to the respective biomass, the intermittently fed reactors presented the highest specific activity. Out of the 22 compounds studied, 17 compounds were removed with more than 20%.

Removal of pharmaceuticals in conventionally treated wastewater by a polishing moving bed biofilm reactor (MBBR) with intermittent feeding.

Previous studies have demonstrated that aerobic moving bed biofilm reactors (MBBRs) remove pharmaceuticals better than activated sludge. Thus we used a MBBR system to polish the effluent of an activated sludge wastewater treatment plant. To overcome that effluent contains insufficient organic matter to sustain enough biomass, the biofilm was intermittently fed with raw wastewater. The capacity of pharmaceutical degradation was investigated by spiking pharmaceuticals. Actual removal during treatment was assessed by sampling the inlets and outlets of reactors. The removal of the majority of pharmaceuticals was enhanced through the intermittent feeding of the MBBR. First-order rate constants for pharmaceutical removal, normalised to biomass, were significantly higher compared to other studies on activated sludge and suspended biofilms, especially for diclofenac, metoprolol and atenolol. Due to the intermittently feeding, degradation of diclofenac occurred with a half-life of only 2.1h and was thus much faster than any hitherto described wastewater bioreactor treatment.