Habibe Elif Gülşen Akbay Habibe Elif Gülşen Akbay MÜHENDİSLİK FAKÜLTESİ ÇEVRE MÜHENDİSLİĞİ BÖLÜMÜ ÇEVRE BİLİMLERİ ANABİLİM DALI
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A novel additive for enhancing biomass energy production from agro-industrial wastes: synthesis of hydrophobic nanoporous silica aerogel and its effect on methane production

Akbay, Habibe Elif Gülşen | Başgöz, Öyküm

Anaerobic digestion (AD) is one of the most preferred processes for the treatment of organic waste. However, additional processes such as co-digestion, pretreatment, and additive addition continue to be explored to remove the limits on the applicability of AD. This study investigated the effects of hydrophobic nanoporous silica aerogel (NpSA) synthesized from waste rice husks on the anaerobic co-digestion (AnCD) of the mixture consisting of sewage sludge and fruit processing industry wastes. All bioreactors containing NpSA-free, 0.1 g, 0.2 g, 0.5 g, and 1 g NpSA (0.03–0.3 gNpSA/gVSadded) were operated in a mesophilic-batch process. Biogas and methane yields increased from 346 mL/gVS (NpSA-free) to 387 mL/gVS and from 231 mL/gVS (NpSA-free) to 288 mL/gVS, respectively, with 0.1 g NpSA addition. NpSA additive increased biogas production in all bioreactors compared to the blank. However, biogas production rate and methane content increased faster at lower doses of NpSA. Maximum soluble chemical oxygen demand (sCOD), protein, carbohydrate, and volatile solid (VS) reductions were between 45–71%, 35–54%, 44–65%, and 34–91% for NpSA added mixtures, respectively. The hydrophobic NpSA additive was effective in improving the AnCD performance and biogas/methane production. Experimental resu...

Enhancement of biohydrogen production efficiency in dark co-fermentation of sewage sludge and fruit processing wastes through ultrasonic, alkali, acid, and thermal pretreatment

Akbay, Habibe Elif Gülşen | Deniz, Fatma

The development of urbanization and related treatment/infrastructure systems has increased the number of wastewater treatment plants in cities and the amount of sewage sludge (SS) with high organic matter content coming out of them. Dark co-fermentation (DcF) of such wastes with industrial wastes of food origin with high carbohydrate (CH) content is quite attractive to produce biohydrogen, which is considered as an efficient alternative fuel of the future. This study aimed to improve batch biohydrogen production by ultrasonic (US), thermal (T), acidic (AC) and alkali (AL) pretreatment of feedstock consisting of SS and various fruit processing industry wastes (3:1 mixing ratio based on total solids (TS)). Biohydrogen production yields were 96.48, 143.95, 121.79, 119.80, 114.73, and 100.32 mL/gCHadded for untreated, T (70 °C), AC (pH: 3), AL (pH: 10), US (5 min), and US (10 min) pretreatments, respectively. However, AC (pH:4), T (100 °C), and AL (pH:8) pretreatments decreased the biohydrogen production yield by 20.2 %, 9.9 %, and 3.4 %, respectively. In this study, it was revealed that there is no linear relationship between the increase in organic matter dissolution after pretreatment and biohydrogen production efficiency after the DcF process. However, kinetic model data designed...

Electrocoagulation and nanofiltration integrated process application in purification of bilge water using response surface methodology

Gözmen, Belgin | Dizge, Nadir | Turabik, Meral | Gülsen, H. Elif

Marine pollution has been considered an increasing problem because of the increase in sea transportation day by day. Therefore, a large volume of bilge water which contains petroleum, oil and hydrocarbons in high concentrations is generated from all types of ships. In this study, treatment of bilge water by electrocoagulation/electroflotation and nanofiltration integrated process is investigated as a function of voltage, time, and initial pH with aluminum electrode as both anode and cathode. Moreover, a commercial NF270 flat-sheet membrane was also used for further purification. Box–Behnken design combined with response surface methodology was used to study the response pattern and determine the optimum conditions for maximum chemical oxygen demand (COD) removal and minimum metal ion contents of bilge water. Three independent variables, namely voltage (5–15 V), initial pH (4.5–8.0) and time (30–90 min) were transformed to coded values. The COD removal percent, UV absorbance at 254 nm, pH value (after treatment), and concentration of metal ions (Ti, As, Cu, Cr, Zn, Sr, Mo) were obtained as responses. Analysis of variance results showed that all the models were significant except for Zn (P > 0.05), because the calculated F values for these models were less than the critical F value...