Enhanced denitrification using high-molecular-weight poly(lactic acid) blended with lactide as an effective carbon source

Chunying Si; Sheng Wang; Zhen Chen; Guoming Hu; Xuanying Zhao; Ping Sun; Quanxing Zhang; Wei Jiang

doi:10.1016/j.biortech.2023.129542

Enhanced denitrification using high-molecular-weight poly(lactic acid) blended with lactide as an effective carbon source

Bioresour Technol. 2023 Nov:387:129542. doi: 10.1016/j.biortech.2023.129542. Epub 2023 Jul 22.

Authors

Chunying Si¹, Sheng Wang¹, Zhen Chen¹, Guoming Hu¹, Xuanying Zhao², Ping Sun¹, Quanxing Zhang¹, Wei Jiang³

Affiliations

¹ State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
² Jiangsu Nanda Huaxing Science and Technology of Environmental Protection Co. Ltd, Yancheng 224001, China.
³ State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China. Electronic address: jiangwei@nju.edu.cn.

PMID: 37482201
DOI: 10.1016/j.biortech.2023.129542

Abstract

The utilization of wasted Poly(lactic acid) (PLA) as low-cost carbon sources in solid-phase denitrification is hindered by its low biodegradability, which can be attributed to its high molecular weight. This study presents a new approach by blending high-molecular-weight PLA with a small amount of ʟ-lactide (PLA/LA_x) to treat nitrate-contaminated wastewater. The addition of ʟ-lactide enhanced the release of carbon from high-molecular-weight PLA. An impressive denitrification efficiency of 96.7% was achieved, accompanied by extremely low levels of accumulated NO₂^--N (0.1 mg/L) and NH₄⁺-N (0.4 mg/L). The quantity of ʟ-lactide used significantly impacted the bacterial community structure. A high abundance of the phyla Bacteroidota and Chloroflexi associated with polymer degradation was observed. The most dominant denitrifier was the genus unclassified_f__Rhodocyclaceae belonged to the phylum Proteobacteria. This study demonstrates that blending PLA with just 5 wt% lactide can transform it into a highly effective solid-phase carbon source to eliminate nitrates.

Keywords: Environmentally friendly; Functional bacterial community; Nitrate-contaminated wastewater; Wasted biodegradable plastics.

MeSH terms

Carbon* / metabolism
Denitrification*
Molecular Weight
Nitrates / metabolism
Polyesters / metabolism

Substances

poly(lactide)
dilactide
Carbon
Polyesters
Nitrates