Atıksu Arıtma Çamurlarının Sürdürülebilir Kullanım Alternatifleri: Öncelikli Yaklaşımlar

Abstract

Atıksu arıtma proseslerindeki mikrobiyal besin zincirinin doğal son ürünleri olan arıtma çamurları, çevre için büyük risk oluşturan atık maddeler arasında sayılmaktadırlar. Arıtma çamurlarının sekonder bir kirletici olarak birikmesi, söz konusu atıkların, işlem gördükten sonra uygun yöntemlerle bertaraf edilmesini zorunlu kılmaktadır. Çamur bertarafı için birçok yöntem bulunmakla birlikte, son yıllarda atıksu arıtma çamurlarının sürdürülebilir kullanımını hedef alan yaklaşımların hem ekonomik, hem de ekolojik açıdan ilgi odağı olduğu görülmektedir. Günümüzün öncelikli yaklaşımları çerçevesinde arıtma çamurları atık bir malzeme olarak düşünülmemekte, geri dönüşümü ya da yeniden kullanımı mümkün olan bir kaynak olarak değerlendirilmektedir. Arıtma çamurlarının yeniden kullanımı kapsamında en yaygın uygulama, stabilize edilen çamurun tarımsal arazilere gübre olarak verilmesidir. Çamurun toprak ortamına girmesiyle, bünyesinde bulunan bitki besin maddeleri ve organik maddeler topraktaki doğal döngülerine katılmakta ve tarımsal üretimde ekonomik kazanç sağlanmaktadır. Ancak son yıllarda yapılan çalışmalar, geleneksel kirleticilerin yanısıra çamurdaki mikrokirleticilerin de çevre ve insan sağlığı için bir tehdit oluşturduğuna dikkati çekmektedir. Bu çalışmaların ortaya koyduğu endişeler, tarım arazilerine yapılan çamur uygulamalarının ölçeğini ve halkın kabulünü kısıtlamaktadır. Bu nedenle, atıksu çamurlarının farklı amaçlarla kullanılmasına yönelik çalışmalara ağırlık verilmiştir. Bu kapsamda, susuzlaştırılmış arıtma çamurları ile çamurların yakılması sonucu elde edilen küller, çimento ve birçok yapı malzemesinin üretiminde katkı maddesi olarak kullanılabilmektedir. Diğer taraftan atıksu çamurundan enerji geri kazanımına yönelik farklı yaklaşımlara sahip pek çok teknoloji geliştirilmiş ve çok sayıda araştırma yapılmıştır. Yakma ve termal enerji geri kazanımı yoluyla elektrik üretimi, atıksu çamuru için popüler bir sürdürülebilir kullanım alternatifi olarak kabul edilmektedir. Ancak çamurun yüksek nem içeriği ve düşük ısıl değeri yüksek enerji tüketimine sebep olmakta ve ek yakıt ihtiyacı söz konusu olabilmektedir. Arıtma çamurlarından elde edilen toplam enerji miktarlarını arttırmak için, kurutma aşamasında harcanan enerjinin azaltılması ve farklı senaryolar ile net enerji dengelerinin sağlanması konularında daha fazla çalışmanın yapılmasına ihtiyaç vardır. Atıksu çamurundan proteinler, enzimler, polihidroksialkanoatlar, biyosürfaktanlar gibi katma değerli ürünlerin elde edilmesi ise, pek çok avantaj sunan ve gelecekteki çamur yönetimi alanında önemli bir yer tutabilecek yenilikçi bir yaklaşımdır. Atıksu çamurundan elde edilebilecek biyo ürünler ve değerli kaynaklar, sürdürülebilir yeşil ürün alternatifleri olarak çok farklı alanlarda kullanılabilme potansiyeline sahiptir. Arıtma çamuru tabanlı biyorafineri süreçlerinin teknolojik-ekonomik performansının daha detaylı olarak ortaya konması için kapsamlı çalışmaların yapılması gerekmektedir.

Keywords

• Atıksu arıtma çamuru
• Sürdürülebilir kullanım
• Yeniden kullanım
• Geri kazanım

Sustainable Utilization Alternatives for Sewage Sludge: Priority Approaches

Abstract

Wastewater sludges, which are the natural end products of the microbial food chain in wastewater treatment processes, are among the waste materials that pose a great risk for the environment. The accumulation of sludge as a secondary pollutant obliges those to be disposed by appropriate methods after being treated. Although there are many methods for sludge disposal, it is seen that the approaches targeting the sustainable use of wastewater sludges have been the focus of interest both economically and ecologically. Within the framework of today's priority approaches, sludge is not considered as a waste material, it is considered as a resource that can be recycled or reused. The most common practice among reuse methods is application of stabilized sludge as fertilizer to agricultural lands. With the entry of sludge into the soil environment, the plant nutrients and organic substances in sludge participate in their natural cycles in the soil and economical gain is achieved in agricultural production. However, recent studies draw attention to the fact that micropollutants in wastewater sludge, as well as traditional pollutants, pose a threat to the environment and human health. Concerns raised by these studies limit the scale of sludge applications to agricultural lands and its public acceptance is reduced. Therefore, many studies have been conducted to use sludges for different purposes. In this context, dewatered sludges and sludge ashes can be used as additives in the production of cement as well as many construction materials. Moreover, many technologies with different approaches to energy recovery from wastewater sludge have been developed and many researches have been carried out. Electricity generation through incineration and thermal energy recovery is considered as a popular sustainable usage alternative for wastewater sludge. However, the high moisture content and low calorific value of the sludge cause high energy consumption and additional fuel demand may occur. In order to increase the total amount of energy obtained from the sludge, further work is needed to reduce the energy spent in the drying phase and to achieve net energy balances with different scenarios. Obtaining value-added products such as proteins, enzymes, polyhydroxyalkanoates, and biosurfactants from wastewater sludge is an innovative approach that offers many advantages and can take an important place in the area of sludge management in the future. Bio products and valuable resources that can be obtained from wastewater sludge have the potential to be used in many different areas as sustainable green product alternatives. Comprehensive studies are required to reveal the technological-economic performances of the sludge-based biorefinery processes.

Keywords

• Wastewater sludge
• Sustainable Usage
• Reuse
• Recovery

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