1. A displacement pump has to be chosen. The most suitable would be a progressive cavity pump or a rotary lobe pump.

2. 8 kg/m³ = 8^o/_oo = 0.8 %32 kg/m³ = 32^o/_oo = 3,2 %

resulting volume: 100m³ * 0,8% / 3,2% = 25m³equals ¼ !

3. Total solids: 200 m³/d * 0.025 * 1000 kg/m³ = 5000 kg/d

500 m³/d * 0.006 * 1000 kg/m³ = 3000 kg/d

(5000 kg/d + 3000 kg/d ) / (200 m³/d +700 m³/d) = 11,4 kg/m³ = 1.14%

- 700 m³/d, 8000 kg/d, 1.14% TS

• maximum solids load: see Table 3  55 kg/(m²*d)

• required surface: 8000 kg / 55 kg/(m²*d) = 145 m², Ø= 13,6 m

• hydraulic overflow rate primary + secondary sludge:

[ (200 m³/d) / (2 h/d) + (500 m³/d) / (24h/d) ] / 145 m³ = 0.83 m/h < 1.0 /h

• hydraulic overflow rate secondary sludge

[ (500 m³/d) / (24h/d) ] / = 0.14 (quite low, adding of process water could be considered)

• depth of compaction zone:

achievable TS-concetration = 5% (table 3), overall 5% * 0,75 = 3.75 %

sludge volume: 8000 kg/d / 37.5 kg/m³ = 213 m³/d

volume of comp. zone: 213 m³/d * 36/24 = 320 m³

depth: 320 m³ / 145 m² = 2.2 m

• overall depth: sedimentation + compaction + scrapers = 1.0 + 2.2 + 0.3 = 3.5 m