The purpose of this project was to investigate the effect of selective particle removal during primary treatment on downstream biological nutrient removal processes. Bench-scale Salsnes Filter fine mesh sieves were used as a primary treatment to obtain different organic fractions to test the effect on denitrification. Activated sludge and moving bed biofilm reactor anoxic tests were performed on municipal wastewater collected from two full-scale wastewater treatment plants located around the Oslo region (Norway). About 43% of the suspended solids in the wastewater was less than 18 μm, and 14% was between 18 and 150 μm. The effect of particulate chemical oxygen demand (COD) removal on denitrification rates was very minor.
Operating experience for the first enhanced biological phosphorus (EBPR) and biological nutrient removal (BNR) plant in Norway are summarized. The primary objective during the first years of operation was to remove phosphorus at low temperatures both in an EBPR mode and a BNR mode. Enhanced biological phosphorus removal was accomplished at 5°C with 0.6 mg/L total phosphorus in the effluent, and BNR was achieved at 6 to 8°C with an average of 0.25 mg/L phosphorus and 5.3 to 9.6 mg/L nitrogen in the effluent. Solids were separated by gravity settling only. Sufficient solids retention time resulted in biological phosphorus and nitrogen removal at low temperatures with two-thirds of the sludge production compared with chemical phosphorus removal. In the approximate plug-flow biological reactor, a completely stirred tank reactor with seven compartments, a mixed liquor suspended solids concentration of 6000 to 8000 mg/L was maintained because of the excellent settling characteristics of the sludge (diluted sludge volume index ϭ 60 to 80 mL/g). Plug-flow mixing characteristics result in a substrate gradient that promotes growth of rapid-settling bacteria and depresses growth of filamentous bacteria. Organic reduction in the anaerobic and anoxic zones results in a low organic loading rate to the aerobic zones with subsequent favorable conditions for nitrification. Water Environ. Res., 72, 444 (2000).KEYWORDS: biological nutrient removal, enhanced biological phosphorus removal, low-strength wastewater, low temperature, organic loading rate, solids production. Credits. The authors thank the plant operators, Rolf Jensen and Leif Å ge Johansen, at Groos BNR WWTP. They also thank students and staff at Agder College for participation in parts of the study and Barry Rabinowitz and Patrick Coleman of Reid Crowther for valuable guidance with plant operation.
The goal of this study was to investigate what kind of impact the removal of particulate organic matter with 33μm rotating belt filter (RBF) (as a primary treatment) will have on the membrane bioreactor (MBR) performance. Two small MBR pilot plants were operated in parallel, where one train treated 2mm screened municipal wastewater (Train A) and the other train treated wastewater that had passed through a RBF with a 33μm filter cloth (Train B). The RBF was operated without a filter mat on the belt. About one third of the organic matter was removed by the fine mesh filter. The assessment of the overall performance showed that the two pilot plants achieved approximately the same removal efficiencies with regard to total suspended solids (TSS), chemical oxygen demand (COD), total phosphorus and total nitrogen. It was also observed that the system with 33μm RBF as a primary treatment produced more sludge, which could be used for biogas production, and required about 30% less aeration downstream. Transmembrane pressure was significantly lower for the train receiving 33μm primary treated wastewater compared to the control receiving 2mm screened wastewater.
The purpose of this project is to render wastewater treatment more attractive in terms of energy use and production by selective removal of organic matter (COD) with Salsnes Filter (SF) technology. Bench-scale SF fine mesh sieves were used as a primary treatment to obtain different organic fractions to test the effect on denitrification. Tests were performed using activated sludge (AS) and moving bed biofilm reactor (MBBR) processes on municipal wastewater collected from two full-scale wastewater treatment plants (wwtps) located around the Oslo region (Norway). It was observed during this study that 70 % of the organic matter was in particulate forms (pCOD). SF fine mesh sieves can remove up to 40 % of the pCOD (18 μm). The effect of pCOD removal on denitrification rates was very minor. For instance, filtration with 1.2 µm filter reduced, on average, the first DN rate by only 4 % and the second DN rate by 14 %.
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