doi:10.1016/j.biosystemseng.2007.01.001
Copyright © 2007 IAgrE Published by Elsevier Ltd.
Effect of Nitrification on Phosphorus dissolving in a Piggery Effluent treated by a Sequencing Batch Reactor
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M.L. Daumer1, 
, 
, F. Béline1, F. Guiziou1 and M. Sperandio2
1Cemagref, Environmental Management and Biological Treatment of Wastes Unit, 17 av.de Cucillé, CS 64427, F-35044 Rennes Cedex, France
2INSA Toulouse, Laboratory of Environmental Process Engineering, 135 av. de Rangueil, F-31077 Toulouse Cedex 4, France
Received 16 May 2006;
accepted 15 January 2007.
Available online 9 March 2007.
The effect of the nitrification on dissolved phosphorus during the treatment of piggery wastewater by a modified sequencing batch reactor has been observed in a previous study. The high solid mineral phosphorus content in the piggery wastewater and the chemical mechanism induced by the fall in pH during the nitrification were proposed to explain this effect. In this work, trials using modified sequencing batch reactors were performed to study the influence of the amount of nitrified nitrogen on pH (and thus solubility of the phosphorus) and determine whether the pH was the main cause of the increased phosphorus dissolving. The dissolved phosphorus was found to increase (up to 3 fold) with the increase in nitrified nitrogen. However, even if the pH was regulated this dissolving still occurred. This could be due to local variations of the pH near the bacterial floc. The modified sequencing batch reactor process management (hydraulic retention time and anaerobic/aerobic step duration) allowed the control of the amount of nitrogen nitrified in one cycle and hence the amount of the phosphorus dissolved.
Fig. 1. Schematic for the pilot equipment, treating piggery wastewaters: 1, storage tank (500 l); 2, buffer tank and the weighing system; 3, reactor (100 l); 4, foam breaker; 5, mixing system; 6, fine bubbles diffuser; 7, pH, redox potential, dissolved oxygen and temperature sensors; 8, system for water addition; 9, gas flow meter; 10, withdrawal and weighing system
Fig. 2. pH variation during the treatment cycle; the arrows indicate the beginning of the aeration step
Fig. 3. Changes in the concentration of dissolved phosphorus calcium and magnesium over a single process cycle in a pilot 100 l sequencing batch reactor (SBR: (a) cycle C1 with hydraulic retention time (HRT) of 20 d and 3 h cycle; (b) cycle C2 with HRT of 20 d and 6 h cycle; (c) cycle C3 with HRT of 20 d and 12 h cycle and cycle C4 with HRT of 10 d and 12 h cycle; 
, Ca; ■, P-PO43− for C4; □P-PO43− for C1, C2, C3; ♦, Mg
Fig. 4. Nitrification curves observed over one cycle for each of the three tests (10 l reactor) and compared to the control trial (100 s reactor); , pH 7; ■, pH 8·2; ◊, inhibited nitrification; 
, control
Fig. 5. Dissolved phosphorus observed over one cycle for each of the three tests (10 l reactor) and compared to the control trial (100 l reactor); , pH 7; ■, pH 8·2; ◊, inhibited nitrification;
, control
Fig. 6. Dissolved magnesium observed over one cycle for each of the three tests (10 l reactor) and compared to the control trial (100 l reactor). , pH 7; ■, pH 8·2; ◊, inhibited nitrification;
, control
Fig. 7. Dissolved calcium observed over one cycle for each of the three tests (10 l reactor) and compared to the control trial (100 l reactor); , pH 7; ■, pH 8·2; ◊, inhibited nitrification;
, control
Table 1.
Raw slurry characteristics; mean of three measurements except for P-PO43− and total P in Set 2 (which are based on single values)
Values in brackets are standard deviations; DM, dry matter; MM, mineral matter; TSS, total suspended solid; COD, chemical oxygen demand.
Table 2.
Operating cycle for each of the trials carried out; HRT, hydraulic retention time; feeding is during the five first minutes of the anoxic stage and discharge in the five last minutes of the aerobic stage
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