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298 94 307/02 Untersuchungen zum Stand der Umsetzung des ... 298 94 307/02 Untersuchungen zum Stand der Umsetzung des ...

bvt.umweltbundesamt.de
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Teil 3 Seite 4-33 In the Federal Republic of Germany, mainly the aerobic treatment method is used for di- rectly discharging plants. Apart from different activation method variations (single-stage, two-stage), also multi-stage plants combined with trickling filters are used. Furthermore, there are also extensive aerated wastewater lagoons. Reference to actual BREF - Prevention of stagnant waste water (4.2.6.1- p. 237) - Treatment of slaughterhouse waste water at municipal WWTPs (4.2.6.2- p. 238) 4.5.3.1 Aerobic activation methods For the full biological treatment of the concentrated wastewater from slaughterhouses and meat production plants, currently the aerobic activation method is mainly used. With single-stage activation plants for the treatment of wastewater from the meat production, only low sludge loads are purposeful. In conventional plants, the BOD5 sludge load should not exceed 0,15 kg/kg × d. The plants should be designed with a purposeful deni- trification. For the activation stages of company wastewater treatment plants, mostly circulation tanks or mixing tanks are used. With the circulation tanks, the activation ditches prevail. Apart from these, there are examples of the utilisation of round ditches in the central sec- ondary clarifier tank. When mixing tanks are used, the activation stage is often designed as a cascade. In such cases, it is recommended for the 1st tank of the cascade to provide the option of sequencing batch reactors, which makes it easier to cope with peak loads and to achieve the weekend equalisation. 4.5.3.1.1 Aerobic Digestion Aerobic digestion combined with either intermittent or alternating denitrification under anoxic conditions Description Biological nitrogen elimination is described in general terms in the Commom waste water and waste gas treatment/management systems in the chemical sector BREF. Aerobic digestion combined with either intermittent or alternating denitrification under anoxic conditions involves simultaneous aerobic and anoxic treatment of waste water, either in separate tanks or in a single tank. The process is controlled by monitoring the concentrations of ammonia and nitrogen oxides. Consequently, a number of aeration devices are automatically switched on or off. For example, a single tank may be divided into aerobic and anoxic zones. During the alternating operational method, individual, se- quentially arranged tanks are operated alternately on an aerobic or anoxic basis which

Teil 3 Seite 4-34 coincides with the simultaneous transfer of effluent between tanks. During the intermittent operational method, the tanks are operated in parallel. Achieved environmental benefits Removal of nitrogen, BOD and COD compounds from high loaded waste water steams, which have not been excluded by other means. Cross media effects Odour problems may be caused. Energy is used, e.g. during aeration. Operational data At one rendering plant where the treatment is applied, it is reported that the effluent is first subject to fat separation, solids removal using cylindrical sieves, flotation, mixing and equalisation. The treatment is then undertaken in large-volume, foil-sealed earth basins. Aeration is carried out intermittently. Full nitrogen elimination through simultaneous nitrification/de- nitrification is reportedly achieved. The main part of the BOD and COD load can be re- moved without aeration. Dimensional and operating data of the aerobic treatment stage is shown in the following table. Table 4-5: Dimensional and operating data of the aerobic treatment stage at a rendering plant Total volumes, aeration tank 1,803 m³ Value de-nitrification:value nitrification (ratio) 0.33 Inflow (Qd) 100 m³/d link to BOB/d and BOD/m 3 ?? Mixed-liquer suspended solids in the aeration tank 3.5 g/l BOD – load 346 kg BOD/d see above NH4-N – load 90 kg NH4-N/d COD:N (ratio) 5.6:1 BOD – volume load 0.19 kg BOD/(m³·d) N – volume load 0,05 kg N /(m³·d) BOD – sludge load 0.05 kg BOD /(kg TS·d) N – sludge load 0.015 kg N /(kg TS·d) Excess sludge incidence ? 66 kg/d Age of sludge (tTS) Is this of special sig- nificance 95 d Specific O2 consumption for BOD 2.09 kg O2/kg BOD

Teil 3 Seite 4-34<br />

coinci<strong>des</strong> with the simultaneous transfer of effluent between tanks. During the intermittent<br />

operational method, the tanks are operated in parallel.<br />

Achieved environmental benefits<br />

Removal of nitrogen, BOD and COD compounds from high loaded waste water steams,<br />

which have not been excluded by other means.<br />

Cross media effects<br />

Odour problems may be caused. Energy is used, e.g. during aeration.<br />

Operational data<br />

At one ren<strong>der</strong>ing plant where the treatment is applied, it is reported that the effluent is<br />

first subject to fat separation, solids removal using cylindrical sieves, flotation, mixing and<br />

equalisation.<br />

The treatment is then un<strong>der</strong>taken in large-volume, foil-sealed earth basins. Aeration is<br />

carried out intermittently. Full nitrogen elimination through simultaneous nitrification/de-<br />

nitrification is reportedly achieved. The main part of the BOD and COD load can be re-<br />

moved without aeration. Dimensional and operating data of the aerobic treatment stage is<br />

shown in the following table.<br />

Table 4-5: Dimensional and operating data of the aerobic treatment stage at a ren<strong>der</strong>ing<br />

plant<br />

Total volumes, aeration tank 1,803 m³<br />

Value de-nitrification:value nitrification<br />

(ratio)<br />

0.33<br />

Inflow (Qd) 100 m³/d link to BOB/d and BOD/m 3 ??<br />

Mixed-liquer suspended solids in the<br />

aeration tank<br />

3.5 g/l<br />

BOD – load 346 kg BOD/d see above<br />

NH4-N – load 90 kg NH4-N/d<br />

COD:N (ratio) 5.6:1<br />

BOD – volume load 0.19 kg BOD/(m³·d)<br />

N – volume load 0,05 kg N /(m³·d)<br />

BOD – sludge load 0.05 kg BOD /(kg TS·d)<br />

N – sludge load 0.015 kg N /(kg TS·d)<br />

Excess sludge incidence ? 66 kg/d<br />

Age of sludge (tTS) Is this of special sig-<br />

nificance<br />

95 d<br />

Specific O2 consumption for BOD 2.09 kg O2/kg BOD

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