초록
<P><B>Abstract</B></P> <P>Waste generation, waste management, sustainable energy production, and global warming are interrelated environmental issues to be considered together. Wastewater treatment sludge is an organic substance rich waste which causes significant environmental problems. However, these wastes can be used as raw material in biofuel generation. This study was designed to investigate the possible utilization of waste sludge in biohydrogen production by taking these facts into consideration. For this purpose, the sludge was first pre-treated with acid and then, the solid (sludge) and liquid (filtrate) phases of acid pre-treated sludge were used as the substrates for biohydrogen generation dark fermentation. Two-factor factorial experimental design method was used in acid hydrolysis of sludge to determine the effect of pH (pH = 2–6) and reaction period (time, min) elution of chemical oxygen demand (COD), total organic carbon (TOC) and total sugar (TS), NH<SUB>4</SUB> N and PO<SUB>4</SUB> P. Statistical evaluation of the results indicated that pH significantly affects the elution of organic carbon and nutrient content of sludge while the reaction time is significant for only organic carbon content. The optimum pretreatment conditions for maximum organic and nutrient elution were determined as pH = 2 and t = 1440 min. The pretreated products, named as filtrate sludge and sludge, conducted to dark fermentation under mesophilic conditions for biohydrogen generation showed that pretreatment of waste sludge at pH = 6 is the best condition giving the maximum yields (Y<SUB>H2</SUB>) as Y<SUB>H2</SUB> = 24 mmol g<SUP>−1</SUP> Total Sugar <SUB>consumed</SUB> and Y<SUB>H2</SUB> = 41 mmol g<SUP>−1</SUP> Total sugar consumed, for filtrate and sludge, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Over 90% carbon and nutrient recovery were achieved by acid hydrolysis of sludge. </LI> <LI> The maximum nutrient and carbon recoveries were obtained at pH = 2 and t = 1440 min. </LI> <LI> Production rate and yield of hydrolyzed sludge were higher than that of raw sludge. </LI> <LI> Filtrate provided 16 times higher production rate than solid phase of sludge. </LI> <LI> The yield from filtrate was 10 times higher than that of solid phase of sludge. </LI> </UL> </P>