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Joanna Czarnota, Adam Masłoń
Rzeszow University of Technology, Poland
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Abstract
The MBBR technology base on the idea of bringing together, within a single system, the best characteristics of the activated sludge and biofilm processes. With biomass immobilised on free-support media, the retention of solids in the biological reactor is enhanced. The advantages of this technology as compared with activated-sludge systems are: a higher effective sludge retention time (SRT) that favours nitrification, more limited production of sludge, more limited requirements as regards area, and resilience to toxic shock. The MMBR technology does not need recirculation of sludge, which is the case with activated-sludge systems, so process performance is independent of a secondary clarifier. Wastewater treatment based on the MBBR process in the same tank favours nitrification, since the issue of the retention time for solids becomes partly uncoupled from the hydraulic retention time. This is particularly important where a WWTP is operating at low temperatures, as under these conditions, the sludge age needed to support nitrification is relatively great, due to the low growth rates achieved by nitrifying bacteria.

The aim of the paper is the evaluation of the effectiveness of a wastewater treatment plant in Nowa Wieś (Poland). The technological system of the Nowa Wieś WWTP consists of an sieve, grit chamber, two reactors with moving bed biofilm (MBBR reactors with the EvU-Perl carriers) and two secondary settling tanks. The study includes an analysis of the efficiency of operation of the Nowa Wieś WWTP in the 2016-2018 period. The assessment of the plant’s efficiency was based on values for pollution indicators in raw and treated sewage made available by the plant operator (i.e. in relation to BOD5, COD, TSS, TN and TP), as well as on the calculated efficiency of removal of particular pollutants.

The average level of efficiency determined for the removal of organic compounds from sewage was 98.9±0.6% (BOD5) and 95.3±2.1% (COD), denoting that the average concentration of these compounds in outflow was of 4.3±2.1 and 43.3±16.7 mg O2∙dm-3 respectively. The average value for the efficiency of removal of total suspended solids was in turn 97.6±1.5%, with the average concentration on discharge equal to 8.3±4.3 mg∙dm-3. Unfortunately, in the analysed years, a dozen or so times (in about 36% of the results) the reduction of biogenic compounds proving achievable was below the level laid down by the permit, i.e. 80.0% for TN and 85.0% for TP. The average efficiencies of removal of nitrogen and phosphorus compounds from wastewater in the analysed period were in fact of 73.7±25.3% and 87.4±10.8% respectively. This denotes that the average concentration of biogenic compounds in treated wastewater was 25.4±24.4 mg TN∙dm-3 and 2.5±3.1 mg TP∙dm-3.

Keywords 
MBBR technology, activated sludge, EvU-Perl carrier material, organic compounds, biogenic compounds

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