Nitrogen Removal for Liquid-Ammonia Mercerization Wastewater via Partial Nitritation/Anammox Based on Zeolite Sequencing Batch Reactor

Lei Zheng,Yuchen Chen,Songwei Zhou,Lijuan Zhang,Xingxing Wang,Yongxing Chen,Xiaojun Wang,Zhenguo Chen

doi:10.3390/w12082234

Lei Zheng, Yuchen Chen + Show 6 more

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https://doi.org/10.3390/w12082234

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Abstract

Liquid-ammonia mercerization is commonly used to enhance the quality of cotton fabric in the textile industry, resulting in a large amount of liquid-ammonia mercerization wastewater (LMWW) containing high concentration of ammonia to be disposed of. This study proposes a partial nitritation/anammox (PN/A) process based on stable nitritation by a zeolite sequencing batch reactor (ZSBR) for the nitrogen removal of LMWW. The ZSBR could quickly achieve stably full nitritation with a nitrite accumulation ratio higher than 97% and an ammonia removal rate of 0.86 kg N·m−3·d−1 for the raw LMWW with an ammonia level of 1490 mg/L. In order to avoid anammox inhibition by free nitrous acid, the ZSBR was successfully changed to PN operation with diluted LMWW for effluent meeting anammox requirements. The next anammox reactor (an up-flow blanket filter (UBF)) realized a total nitrogen removal efficiency of 70.0% with a NLR (nitrogen loading rate) of 0.82 kg N·m−3·d−1 for LMWW. High-throughput sequencing analysis results indicated that Nitrosomonas and Candidatus Kuenenia were the dominant bacteria in ZSBR and UBF, respectively. All results revealed that the PN/A process based on ZSBR as the PN pretreatment process was feasible for LMWW, facilitating cost-effective and low-carbon nitrogen removal for LMWW treatment in the textile industry in the future.

Highlights

Since pure cotton is well-known to have greater breathability and hygroscopicity than chemical fiber materials, clothes made from cotton are softer and more comfortable
Proposed a novel pH-dissolved oxygen (DO) control strategy and observed apparent nitrite-oxidizing bacteria (NOB) inhibition and the promotion of ammonium-oxidizing bacteria (AOB) after 33 days of operation, while the nitrite accumulation ratio (NAR) increased to 90%
This study found that high DO (>4 mg/L) could not promote NOB activity and efficient nitrite accumulation was obtained in zeolite sequencing batch reactor (ZSBR)

Summary

Introduction

Since pure cotton is well-known to have greater breathability and hygroscopicity than chemical fiber materials, clothes made from cotton are softer and more comfortable. These kinds of clothes always have poor wrinkle resistance and are likely to deform or shrink after long wear and numerous washes. This problem can be greatly improved by mercerizing cotton fabric [1]. Compared to the traditional mercerization process, the new mercerized finish technological process, employing liquid-ammonia, helps to improve tactile impression, abrasive resistance, and wrinkle. Cotton fabric processed by liquid-ammonia mercerization is known as a high-end product in the market

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