Publication: Monitoring of anammox bacteria under gradually increasing heavy metal concentrations
Abstract
Enerji ve maliyet verimli nitrojen giderimi için umut vaadeden bir teknoloji olarak anammox keşfinden beri pek çok araştırmacının ilgisini geçmiştir. Gerçek ölçekli anammox uygulamalarının sayısındaki artışa rağmen bu uygulamanın yaygınlaşması düşük büyüme hızı, yüksek sıcaklık ve nitrojen ihtiyacı ve organikler, tuzlar, fosfat, sülfat ve ağır metaller gibi inhibitörlere değişken tepkiler vermesiyle kısıtlanmıştır. Bu inhibitör maddeler arasında ağır metaller özellikle endüstriyel atık sularda ve katı atık sızıntı suyunda sıklıkla bulunur. Literatürde ağır metallerin anammox üzerindeki etkileriyle ilgili çalışmalar bulunabilir, fakat bu çalışmalar genellikle proses mühendisliği bakış açısıyla işletme parametrelerine odaklanmıştır. Anammox prosesinde ağır metal inhibisyonunun daha kapsamlı anlayabilmek için detaylı bir moleküler inceleme gerekmektedir. Dahası, literatürdeki çoğu rapor kısa süreli maruziyetlerin anammox üzerindeki etkileri hakkında bilgi vermektedir; uzun süreli maruziyetlerin incelenmesi gerçek ölçekli anammox prosesleri için oldukça önemlidir.Bu çalışma kapsamında uzun süreli Bakır (Cu (II)) ve Kadmiyum (Cd(II)) maruziyetlerinin zenginleştirilmiş anammox kültürü üzerindeki etkileri incelenmiştir. Yeni nesil dizi analizi ile Bakır ve Kadmiyum maruziyet reaktörlerindeki baskın tür Candidatus Kuenenia olarak belirlenmiştir. Bunun yanı sıra Candidatus Brocadia ve Candidatus Scalindua varlığı da yeni nesil dizi analizi ve floresan in situ hibridizasyonu ile doğrulanmıştır. Maruziyet sırasında sistemdeki anammox bakterileri dalgalı bir profil göstermiştir; ilk maruziyetin hemen ardından Candidatus Kuenenia miktarı önemli biçimde azalmış, bir süre sonra adaptasyona bağlı olarak tekrar artmış ve son olarak 2,75 mg/ L Cd(II) veya 5,5 mg/ L Cu(II) ile elimine edilmiştir. Çok düşük metal konsantrasyonlarında bile sistemden atılan Candidatus Scalindua aksine Candidatus Brocadia ağır metal maruziyetinde büyüme eğilimi göstermiştir.
Since its discovery, anammox have caught the attention of many researchers as a promising technology for cost and energy efficient nitrogen removal. Despite the increasing number of full-scale anammox applications, spreading of this process has been limited by different factors like its slow growth rate, high temperature and nitrogen load needs, and its highly variable responses to the common inhibitory substances like organics, salts, phosphate, sulphate and heavy metals. Among these inhibitory substances, heavy metals are frequently found in wastewaters, especially in industrial discharges and landfill leachates. Numbers of research papers about effects of heavy metals on anammox can be found in the literature, but mostly with a focus on operating parameters with the perspective of process engineering. A detailed molecular examination is a necessity for the deeper understanding of heavy metal inhibition on anammox process. Furthermore, most of the reports in the literature focus about short-term exposures of heavy metals on anammox process, whereas investigation of long-term exposures is all important for full-scale anammox applications.In the scope of this study, effects of long-term Copper (Cu(II)) and Cadmium (Cd(II)) exposures on enriched anammox culture were monitored. Dominant genus in both Cu(II) and Cd(II) exposure reactors was determined as Candidatus Kuenenia by next-generation sequencing (NGS). Besides, the existence of Candidatus Brocadia and Candidatus Scalindua were confirmed by next-generation sequencing and fluorescence in-situ hybridization (FISH). During the exposures, anammox bacteria in the system showed a fluctuating profile, right after the first exposure Candidatus Kuenenia lessened significantly, after a while started to increase again due to self-adaptation and finally eliminated by 2.75 mg/ L Cd(II) or 5.5 mg/ L Cu(II) concentrations. Candidatus Brocadia showed a tendency to growth under both Cd(II) and Cu(II) exposures unlike the Candidatus Scalindua which was washed out from the system even at very small heavy metal concentrations.
Since its discovery, anammox have caught the attention of many researchers as a promising technology for cost and energy efficient nitrogen removal. Despite the increasing number of full-scale anammox applications, spreading of this process has been limited by different factors like its slow growth rate, high temperature and nitrogen load needs, and its highly variable responses to the common inhibitory substances like organics, salts, phosphate, sulphate and heavy metals. Among these inhibitory substances, heavy metals are frequently found in wastewaters, especially in industrial discharges and landfill leachates. Numbers of research papers about effects of heavy metals on anammox can be found in the literature, but mostly with a focus on operating parameters with the perspective of process engineering. A detailed molecular examination is a necessity for the deeper understanding of heavy metal inhibition on anammox process. Furthermore, most of the reports in the literature focus about short-term exposures of heavy metals on anammox process, whereas investigation of long-term exposures is all important for full-scale anammox applications.In the scope of this study, effects of long-term Copper (Cu(II)) and Cadmium (Cd(II)) exposures on enriched anammox culture were monitored. Dominant genus in both Cu(II) and Cd(II) exposure reactors was determined as Candidatus Kuenenia by next-generation sequencing (NGS). Besides, the existence of Candidatus Brocadia and Candidatus Scalindua were confirmed by next-generation sequencing and fluorescence in-situ hybridization (FISH). During the exposures, anammox bacteria in the system showed a fluctuating profile, right after the first exposure Candidatus Kuenenia lessened significantly, after a while started to increase again due to self-adaptation and finally eliminated by 2.75 mg/ L Cd(II) or 5.5 mg/ L Cu(II) concentrations. Candidatus Brocadia showed a tendency to growth under both Cd(II) and Cu(II) exposures unlike the Candidatus Scalindua which was washed out from the system even at very small heavy metal concentrations.