Improving the efficiency of wastewater sludge pretreatment by high temperature hydrolysis before digestion

Summary

The results of investigating activated sludge and primary sludge thermal pretreatment with the purpose of improving the efficiency of anaerobic digestion are presented. The highest efficiency of activated sludge organics transfer into readily soluble form is ensured after thermal hydrolysis at 160°C. The solubility of primary sludge organic matter increases evenly with the temperature increase in the range of 100–200 °С. The maximum biogas output in the ultimate digestion test is increasing after activated sludge hydrolysis at 160°С, primary sludge hydrolysis – at 180–200°С. Digestion in a continuous mode after activated sludge pretreatment at 140–160 °С results in 53% gas generation increase. Any further hydrolysis temperature increase produces a negative impact on gas generation and disintegration of activated sludge ashless matter. Thermal hydrolysis of primary sludge in thermophilic mode is not efficient. Pretreated sludge dewatering performance is improved; consequently the flocculant dosage can be reduced by 0.8–1.0 kg/t DS.

Key words

energy efficiency , sludge , fermentation , biogas , dewatering performance , thermal hydrolysis

Tackling the problem of energy saving in the Saint-Petersburg wastewater system

Summary

The technologies of primary and secondary sludge treatment at the Saint-Petersburg wastewater treatment facilities are considered. The technologies of thermal hydrolysis and thermophilic and mesophilic digestion were suggested by European companies PWT (Germany), Veolia (OTV, France) and Cambi (Norway). Implementing the project of using the energy potential of wastewater sludge will allow Saint-Petersburg Vodokanal PUE to gain unique experience of systematic approach to the solution of sludge utilization problem.

Key words

sludge , fermentation , biogas , methane tank , mesophilic process , thermophilic process , thermal hydrolysis

Reconstruction of Typical Radial Settling Tanks with the Use of a Scraper System Finnchain

Summary

Difficulties of the operation of radial primary and secondary settling tanks with typical equipment for sludge removal (sludge disposal trucks IBR and sludge scrapers IPR) are stated. The scraper system Finnchain (Finland) devoids these shortcomings. A principle of operation of this equipment is described; basic operation data and its distinctions from analogues are presented.

Key words

sedimentation tank , sludge , sludge disposal truck , sludge scraper , fermentation , removal of nitrogen and phosphorus