Influence of pH and temperature on soluble substrate generation with primary sludge fermentation

Emine Ubay Cokgor, Seda Oktay, Didem Okutman Tas, Gulsum Emel Zengin, Derin Orhon*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

82 Citations (Scopus)


The study was undertaken to evaluate the effect of pH and temperature control on the generation of soluble fermentation products from primary sludge. The effect was tested by running parallel experiments under pH and temperature controlled and uncontrolled conditions. In fermentation experiments conducted at 20 °C without pH control, the average soluble COD release was 14 mg per liter of wastewater treated, representing a potential increase of 5% in the biodegradable COD content of the primary sedimentation effluent. The corresponding average VFA generation was 9.2 mg COD l-1. The nutrient release was practically negligible and stayed at 0.4 mg l-1 for nitrogen and 0.1 mg l-1 for phosphorus. Acetic acid accounted more than 45% of the generated VFA in all experimental runs. The acetic acid content of the VFA decreased with increasing initial VSS concentrations and higher pH levels. VFA generation by fermentation was significantly affected with temperature and pH control. Temperature change between 10 and 24 °C induced a five-fold increase in VFA generation, from 610 mg l-1 at 10 °C to 2950 mg l-1 at 24 °C.

Original languageEnglish
Pages (from-to)380-386
Number of pages7
JournalBioresource Technology
Issue number1
Publication statusPublished - Jan 2009


This study was supported by the Scientific and Technical Council of Turkey (TUBITAK) with ICTAG C018 project number. The contribution of D. Orhon was partly supported by the Turkish Academy of Sciences.

FundersFunder number
Scientific and Technical Council of Turkey
Türkiye Bilimler Akademisi


    • COD fractions
    • Mass balance
    • Nutrient removal
    • Soluble fermentation products
    • Volatile fatty acids


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