Atık Yağ, Gres ve Lipid Maddeleri ile Uzun Zincirli Yağ Asitlerinin Anaerobik Prosesle Arıtılabilirliği Üzerine Derleme Çalışması

Abstract

Bu derleme çalışması kapsamında yağ, gres ve lipid maddelerinden (YGLM) anaerobik biyoteknoloji ile biyoenerji eldesi, atıksulardaki kaynakları, oluşumları, biyolojik parçalanma özellikleri, anaerobik arıtım mikrobiyolojisi ve uygulamaları incelenmiştir. Etkin YGLM giderimi gerçekleştiren gerçek ölçekli anaerobik proses uygulamalarına ait bilgi ulusal literatürde bulunmamakta ve mevcut uygulamalar kentsel çamur çürütme ile endüstriyel ölçekte atıksulardan kolay ayrışabilir organik madde giderimi ile sınırlı kalmaktadır. Hindistan ve Çin gibi fosil yakıt kaynağı bulunmayan ülkelerde evsel atıksuların da anaerobik arıtıma yönlendirilmesi, bu prosesin uygulama potansiyelinin geniş kapsamını göstermektedir. YGLM evsel ve birçok endüstriyel atıksu/atıkta farklı konsantrasyonlarda bulunurken sonraki biyolojik arıtım performansını korumak için çoğunlukla yağ ayırma ünitelerinde atık olarak atıksulardan ayrılmakta ve depolama sahalarına veya çimento fabrikalarına gönderilerek uzaklaştırılmaktadır. Mevcut durumda aerobik prosesle işletilen ve yüksek maliyetlere yol açan endüstriyel atıksu arıtımında anaerobik prosesin yaygınlaşması ve YGLM’nin enerji kaynağı olarak prosese katılması önemli ekonomik katkı sağlayacaktır. YGLM’nin yüksek metan/enerji eldesine dönüşüm potansiyelinin optimum şekilde açığa çıkması için uygun reaktör tipi seçimi ile organik yükleme hızı (OYH), besleme modu ile inhibisyon önleme gibi özel proses işletim şartları gerekmektedir. Bu çalışma, yenilenebilir enerji kaynağı olarak YGLM’nin anaerobik prosesle değerlendirilmesine yönelik sahada arıtım ile akademik araştırma çalışmalarına katkı sağlaması amacıyla literatürde verilen teorik ve uygulama bilgilerinin derlenmesi ile oluşturulmuştur. YGLM’nin ilk basamak hidroliz reaksiyonunda oluşan ara ürünlerin yüksek sayıda C zincirli ve hidrofobik yapıları nedeniyle anaerobik mikroorganizmalar üzerinde inhibisyon etkisi oluşmakta, biyokütlenin reaktörde flotasyonu ve sonrasında kaçışı ile proses bozulması gerçekleşmektedir. Yapılan ilk arıtım çalışmalarında inhibisyon etkisinin kontrolünde toplam yağ asidi konsantrasyonunun eşik değeri belirlenmiş fakat ilerleyen araştırmalarda farklı yağ asidi türleri için farklı inhibisyon değerleri ve etkileri belirlenmiştir. Ardışık anaerobik reaksiyonlarla yağ asitlerinin oksidasyon hızını ve yönünü etkileyen önemli mikrobiyal reaksiyonlar belirlenmiştir. Kesikli besleme modu, reaktörde biyokütle tutunumu sağlayan düşük OYH, floküler çamur ve mezofilik sıcaklık seviyesi gibi işletim koşulları ile yeterli seyrelme sağlayan reaktör tipleri uygun bulunmuştur. Ayrıca protein içerikli atıklarla çoklu anaerobik çürütmenin avantaj ve potansiyeli belirtilmiştir.

Keywords

• Yağ
• Gres
• Lipid
• anaerobik
• arıtım
• yenilenebilir enerji
• uzun zincirli yağ asitleri
• inhibisyon
• işletim

A Review on the Anaerobic Treatability of the Waste Oil, Fat, Grease and Lipid Materials and Long Chain Fatty Acids

Abstract

In this study, origins, characteristics, anaerobic treatability studies and applications including related microbiology were reviewed towards the removal and energy gain from fat, oil and grease (FOG) matter and their intermediate products present in the wastewaters. This review was aimed to contribute to the national literature and design of the full-scale applications on efficient conversion of FOG matter in waste and wastewaters to biogas using anaerobic treatment as nationwide applications are mostly limited to industrial wastewaters with biodegradable soluble organic wastes at industrial scale. Operational biogas plants receive mostly organic wastes originating from animal husbandry and agricultural activities at pre-described rates by the manufacturers. Worldwide applications proved the large range of feasibility for anaerobic process from complex wastes to dilute municipal wastewater. FOG is present in many industrial and municipal wastewaters but mostly separated in DAF units and disposed in landfills or cement factories. FOG presents a high potential for energy recovery in the form of methane gas through anaerobic biotechnology. Performance data were presented regarding to optimum operational characteristics and reactor choice for implementation in the field. Specific operational parameters as organic loading rate (OLR), feeding mode and prevention of inhibition are required to achieve the potential due to the first and slow hydrolysis stage and intermediate products which possess high C number and low solubility in water (hydrophobic) inducing low degradability and inhibitory characteristics. Hydrophobic fatty acids get adsorbed on the bacterial cell wall, prevent the transfer of materials essential to cell metabolism and promote the biomass float and getting washed out of the reactor where biomass immobilization is crucially important to overcome the inhibitory effect. Failure of the process is the gradual result disabling longterm operation. First research studies focused on the threshold value for the total fatty acid concentration tolerable before the start of inhibition and then single fatty acid characteristics were investigated. Several activities conducting and promoting beta-oxidation of fatty acids were stated. Sequential feeding, low OLR, biomass immobilization and reactors enabling sufficient dilution were emphasized for optimum conversion of FOG to methane. Additionally, co-digestion with proteinaceous wastes were presented with synergetic advantages.

Keywords

• Fat
• Oil
• Grease
• Anaerobic
• Treatment
• Renewable Energy
• Long Chain Fatty Acids
• Inhibition
• Operation

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