Microwave Effects on Soluble Substrate and Thermophilic Digestibility of Activated Sludge

Abstract

Thickened waste-activated sludge (TWAS) was subjected to microwave pretreatment and athermal irradiation. The soluble phase of each type of TWAS pretreatment was subject to ultrafiltration in series using progressively smaller pore-size membranes (300, 100, 10, and 1 kDa) and biodegradability tests. Microwave pretreatment solubilizes a considerable amount of the suspended organic substrate, but athermal irradiation also causes solubilization of organic matter, although at a smaller scale than microwave. Proteins are particularly sensitive to athermal irradiation, and both microwave and athermal irradiation are capable of changing the size distribution of dissolved organic matter. Athermal irradiation and microwave have a substantially different effect on thermophilic anaerobic biodegradability of the various size fractions obtained after ultrafiltration. Slight inhibition and decrease in total biogas production was measured in some microwave tests. Athermal irradiation does not cause a decrease in maximum biogas production rate in any test and increases slightly biogas production.

Microwave and ultrasound pre-treatments influence microbial community structure and digester performance in anaerobic digestion of waste activated sludge

“…Microwave irradiation is another, relatively new, technique identified as an energy-efficient alternative to conventional thermal pre-treatment (Mudhoo and Sharma 2011). A combination of thermal and athermal effects has been postulated as the mechanism for sludge disintegration by microwave treatment, with the latter involving the interruption of hydrogen bonds due to rapid changes in dipole orientation of cell membrane macromolecules (Coelho et al 2014;Eskicioglu et al 2007).…”

Superparamagnetic Iron Oxide Nanoparticles as Additives for Microwave-Based Sludge Prehydrolysis: A Perspective

“…High temperatures can also decrease solubility of gases and enable formation of gas domains (bubbles) in the slurry and cause additional stress for cell walls by pressure release if they interact with the cells . On the other hand, elevated temperatures (70–180 °C) were reported to cause low-molecular-weight sugars and amino acids to polymerize and form recalcitrant polymer-like organic compounds via Maillard reactions potentially deteriorating the performance of AD. ,,,− Nonthermal MW effects or direct MW interactions are caused by polar and polarizable molecules rapidly oscillating under the incoming electromagnetic waves. The MW energy is converted to heat by internal resistance to rotation, ,, possibly triggering bond decomposition. , Nonthermal MW decomposition pathways are speculative in the literature, and these effects are still unknown.…”

Düzenli Depolama Alanlarından Sızıntı Suyunun Mikrodalga Işınlama ile Arıtılmasına Genel Bakış

“…MD ile dezentegrasyonda, hedef sıcaklık, sıcaklık yükselme hızı, uygulama süresi vb. işletim koşulları atık içeriğindeki organik maddenin çözünürlüğünü etkilemektedir [139][140][141]. 160-180 °C gibi yüksek sıcaklıklar ve uzun uygulama süreleri (30-60 dak.…”

“…), atık biyolojik çamurların parçalanmasında optimum işletim koşulları olarak belirtilmesine rağmen [142], yüksek sıcaklıklarda organik madde yapısının bozulması ile anaerobik çürütme sürecinde CH 4 gaz hacminde azalmaya neden olmaktadır. Öte yandan, yüksek sıcaklıkların (180°C) düşük moleküler ağırlıklı şekerlerin ve amino asitlerin polimerize olmasına ve Maillard reaksiyonları (karamelizasyon) yoluyla yeniden kalsitrant polimer benzeri organik bileşikler oluşturmasına neden olması, MD sürecini takip eden anaerobik çürütme süreç performansını bozmaktadır [139,141]. Çözünür KOİ'nin CO 2 'e dönüşümü meydana gelebileceğinden, 120°C' nin üzerindeki yüksek sıcaklıklarda çözünür KOİ'de bir azalma olasıdır [143].…”