Details

Autor(en) / Beteiligte

• Kong, Zheng
• Wang, Zhiyao
• Lu, Xi
• Song, Yunqian
• Yuan, Zhiguo
• Hu, Shihu

Titel

Significant in situ sludge yield reduction in an acidic activated sludge system

Ist Teil von

• Water research (Oxford), 2024-09, Vol.261, p.122042, Article 122042

Ort / Verlag

England: Elsevier Ltd

Erscheinungsjahr

2024

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• •An acidic-activated sludge process was stably operated under pH of 4.7 for 400 days.•The acidic system achieved 58 % lower sludge yield than the neutral system.•Settleability and organic matter removal did not deteriorate in acidic systems.•Low pH and in-situ FNA enhanced both cryptic growth and energy uncoupling. Minimizing sludge generation in activated sludge systems is critical to reducing the operational cost of wastewater treatment plants (WWTPs), particularly for small plants where bioenergy is not recovered. This study introduces a novel acidic activated sludge technology for in situ sludge yield reduction, leveraging acid-tolerant ammonia-oxidizing bacteria (Candidatus Nitrosoglobus). The observed sludge yield (Yobs) was calculated based on the cumulative sludge generation and COD removal during 400 d long-term operation. The acidic process achieved a low Yobs of 0.106 ± 0.004 gMLSS/gCOD at pH 4.6 to 4.8 and in situ free nitrous acid (FNA) of 1 to 3 mg/L, reducing sludge production by 58 % compared to the conventional neutral-pH system (Yobs of 0.250 ± 0.003 gMLSS/gCOD). The acidic system also maintained effective sludge settling and organic matter removal over long-term operation. Mechanism studies revealed that the acidic sludge displayed higher endogenous respiration, sludge hydrolysis rates, and higher soluble microbial products and loosely-bounded extracellular polymer substances, compared to the neutral sludge. It also selectively enriched several hydrolytic genera (e.g., Chryseobacterium, Acidovorax, and Ottowia). Those results indicate that the acidic pH and in situ FNA enhanced sludge disintegration, hydrolysis, and cryptic growth. Besides, a lower intracellular ATP content was observed for acidic sludge than neutral sludge, suggesting potential decoupling of catabolism and anabolism in the acidic sludge. These findings collectively demonstrate that the acidic activated sludge technology could significantly reduce sludge yield, contributing to more cost- and space-effective wastewater management. [Display omitted]