Enhancing Anaerobic Digestion of Simulated Plateau Blackwater with Highland Barley Straw Biochar
Tian Shuai
School of Engineering, Xizang Minzu University, Xianyang, China, Key Laboratory of Water Quality Safety and Water Environment Health of Xizang Autonomous Region, China and Key Laboratory of Water Pollution Control and Ecological Restoration of State Ethnic Affairs Commission, Xizang, China.
Hao Yubo
School of Engineering, Xizang Minzu University, Xianyang, China, Key Laboratory of Water Quality Safety and Water Environment Health of Xizang Autonomous Region, China and Key Laboratory of Water Pollution Control and Ecological Restoration of State Ethnic Affairs Commission, Xizang, China.
Zhao Yimin
School of Engineering, Xizang Minzu University, Xianyang, China, Key Laboratory of Water Quality Safety and Water Environment Health of Xizang Autonomous Region, China and Key Laboratory of Water Pollution Control and Ecological Restoration of State Ethnic Affairs Commission, Xizang, China.
Gao Shuangqian
School of Engineering, Xizang Minzu University, Xianyang, China, Key Laboratory of Water Quality Safety and Water Environment Health of Xizang Autonomous Region, China and Key Laboratory of Water Pollution Control and Ecological Restoration of State Ethnic Affairs Commission, Xizang, China.
Guo Xinyu
School of Engineering, Xizang Minzu University, Xianyang, China, Key Laboratory of Water Quality Safety and Water Environment Health of Xizang Autonomous Region, China and Key Laboratory of Water Pollution Control and Ecological Restoration of State Ethnic Affairs Commission, Xizang, China.
Li Shuping
School of Engineering, Xizang Minzu University, Xianyang, China, Key Laboratory of Water Quality Safety and Water Environment Health of Xizang Autonomous Region, China and Key Laboratory of Water Pollution Control and Ecological Restoration of State Ethnic Affairs Commission, Xizang, China.
Zhu Mingchao *
School of Engineering, Xizang Minzu University, Xianyang, China, Key Laboratory of Water Quality Safety and Water Environment Health of Xizang Autonomous Region, China and Key Laboratory of Water Pollution Control and Ecological Restoration of State Ethnic Affairs Commission, Xizang, China.
Meng Jiang
School of Engineering, Xizang Minzu University, Xianyang, China, Key Laboratory of Water Quality Safety and Water Environment Health of Xizang Autonomous Region, China and Key Laboratory of Water Pollution Control and Ecological Restoration of State Ethnic Affairs Commission, Xizang, China.
*Author to whom correspondence should be addressed.
Abstract
Background: Anaerobic digestion of blackwater is attractive for sanitation and resource recovery in high-altitude regions, but low pressure, low oxygen availability and cold stress can slow hydrolysis, acid conversion and methanogenesis.
Aims: This study evaluated whether biochar produced from locally available highland barley straw can improve blackwater digestion under simulated plateau conditions.
Study Design: Batch adsorption and anaerobic digestion experiments were performed using highland barley straw biochars prepared at 300-700 ℃, with the 600 ℃ biochar selected for digestion tests.
Methodology: Ammonium removal was monitored for 4320 min using an initial NH4+-N concentration of about 30 mg/L. Anaerobic digestion was conducted in 2 L reactors at 65 kPa, with a highland control (HC) and a biochar-amended group (HB, 5 g/L). Chemical oxygen demand (COD), pH, volatile fatty acids (VFAs) and cumulative methane were followed for 30 d.
Results: The 600 ℃ biochar achieved 98.77% NH4+-N removal and an equilibrium adsorption capacity of 2.54 mg/g. Adsorption followed a pseudo-second-order model (R2 = 0.981), indicating a dominant chemisorption contribution. Biochar raised final COD removal from 96.09% to 98.01% and shortened the time needed to reach COD below 60 mg/L from 24 to 18 d. Cumulative methane increased from 118.96 to 146.35 mL/g COD, while the fitted maximum methane production rate increased by 88.31%.
Conclusion: Highland barley straw biochar can simultaneously retain ammonium, accelerate COD removal and improve methane recovery from simulated plateau blackwater. The approach links sanitation improvement with straw valorization and provides a low-cost route for decentralized treatment in plateau agricultural and pastoral settlements.
Keywords: Plateau blackwater, highland barley straw, biochar, anaerobic digestion, ammonium adsorption, methane recovery