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    Co-removal of P-nitrophenol and nitrate in sulfur-based autotrophic and methanol-fed heterotrophic denitrification bioreactors
    (Elsevier Sci Ltd, 2023) Yenilmez, Aylin Ebru; Ertul, Selin; Yilmaz, Tulay; Ucar, Deniz; Di Capua, Francesco; Sahinkaya, Erkan
    P-nitrophenol (PNP) can co-occur with nitrate (NO3-) in industrial and municipal wastewater due to effluent discharges from industry and agricultural activities. In this study, the simultaneous removal of PNP and NO3- was investigated under autotrophic and heterotrophic denitrifying conditions in two bioreactor columns at laboratory scale. Autotrophic denitrification with elemental sulfur showed efficient elimination of both PNP (85 % on average for 5-50 mg/L) and NO3- (99 % on average) even at feed PNP concentration of 50 mg/L. In contrast, the heterotrophic column showed significantly lower PNP removal (53 % on average for 5-50 mg/L) despite denitrification efficiency being >= 95 %. ORP was identified as a possible control parameter to modulate PNP removal efficiency. The autotrophic column showed better resiliency than the heterotrophic one under intermittent feeding of 50 mg/L of PNP. Absorbance spectra and HPLC results revealed no accumulation of PNP by-products, i.e., aminophenol, in the autotrophic column during transient feeding conditions.
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    Effects of trace elements (Fe, Cu, Ni, Co and Mg) on biomethane production from paper mill wastewater
    (Walter De Gruyter Gmbh, 2023) Toprak, Dilan; Yilmaz, Tulay; Gulpinar, Kerem; Yucel, Amine; Cakmak, Yakup; Ucar, Deniz
    Trace elements have a significant effect on biochemical reactions and therefore the presence of optimum levels of trace elements is essential for bioreactor performances. In this study, the effects of five trace elements on biomethane production have been investigated. Experimental studies have been carried out with multiple batch reactors at 15 day HRT and mesophilic temperatures. The optimum concentrations for each of the trace elements Fe, Cu, Ni, Co and Mg were found as 5, 0.5, 0.5, 0.5 and 100 mg/L, respectively. Among tested trace elements, Cu was the one which provided the highest biomethane production. Cu addition was resulted in a 46 % increase in biomethane production followed by Co with 24 %. The biomethane production rate for these two trace elements was 191.70 and 110.77 ml CH4/g COD, respectively. Optimum levels for Ni, Fe and Mg increased biomethane production rate by approximately 14.3, 10 and 17 % compared to control groups, respectively. Because the exact amount of trace element requirement for each industry/reactor is different, specific case studies should be performed for each application. These results could be used as initial trace element concentrations for further continuous studies.
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    Sequential sulfur-based denitrification/denitritation and nanofiltration processes for drinking water treatment
    (Academic Press, 2021) Asik, Gulfem; Yilmaz, Tulay; Di Capua, Francesco; Uçar, Deniz; Esposito, Giovanni; Sahinkaya, Erkan
    Efficient and cost-effective solutions for nitrogen removal are necessary to ensure the availability of safe drinking water. This study proposes a combined treatment for nitrogen-contaminated groundwater by sequential autotrophic nitrogen removal in a sulfur-packed bed reactor (SPBR) and excess sulfate rejection via nanofiltration (NF). Autotrophic nitrogen removal in the SPBR was investigated under both denitrification and denitritation conditions under different NO3− and NO2− loading rates (LRs) and feeding strategies (NO3− only, NO2− only, or both NO3− and NO2− in the feed). Batch activity tests were carried out during SPBR operation to evaluate the effect of different feeding conditions on nitrogen removal activity by the SPBR biofilm. Bacteria responsible for nitrogen removal in the bioreactor were identified via Illumina sequencing. Dead-end filtration tests were performed with NF membranes to investigate the elimination of excess sulfate from the SPBR effluent. This study demonstrates that the combined process results in effective groundwater treatment and evidences that an adequately high nitrogen LR should be maintained to avoid the generation of excess sulfide.