Evaluation of a Full-Scale Suspended Sludge Deammonification Technology Coupled with an Hydrocyclone to Treat Thermal Hydrolysis Dewatering Liquors

Pascal Ochs,Ana Soares,Po-Heng Lee,Zhuoying Wu,Tom Stephenson,Benjamin D Martin,Eve Germain,Mark Van Loosdrecht

doi:10.3390/pr9020278

Abstract

Suspended sludge deammonification technologies are frequently applied for sidestream ammonia removal from dewatering liquors resulting from a thermal hydrolysis anaerobic digestion (THP/AD) process. This study aimed at optimizing the operation, evaluate the performance and stability of a full-scale suspended sludge continuous stirred tank reactor (S-CSTR) with a hydrocyclone for anaerobic ammonia oxidizing bacteria (AMX) biomass separation. The S-CSTR operated at a range of nitrogen loading rates of 0.08–0.39 kg N m−3 d−1 displaying nitrogen removal efficiencies of 75–89%. The hydrocyclone was responsible for retaining 56–83% of the AMX biomass and the washout of ammonia oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was two times greater than AMX. The solid retention time (SRT) impacted on NOB washout, that ranged from 0.02–0.07 d−1. Additionally, it was demonstrated that an SRT of 11–13 d was adequate to wash-out NOB. Microbiome analysis revealed a higher AMX abundance (Candidatus scalindua) in the reactor through the action of the hydrocyclone. Overall, this study established the optimal operational envelope for deammonification from THP/AD dewatering liquors and the role of the hydrocyclone towards maintaining AMX in the S-CSTR and hence obtain process stability.

Highlights

Deammonification is an ammonia removal process widely used to remove ammonia from sludge dewatering liquors after anaerobic digestion (AD)
sludge continuous stirred tank reactor (S-CSTR) of this study was slightly lower when compared with other studies
Thefirst first part the analysis focused the ammonia removal and process stability

Summary

Introduction

Deammonification is an ammonia removal process widely used to remove ammonia from sludge dewatering liquors after anaerobic digestion (AD). In THP, steam (160–180 ◦ C) is applied to the sludge, changing the sludge rheology, breaking down complex macromolecules and promoting hydrolysis [1]. This enables the loading rate to the AD to be increased, which subsequently increases the biogas production [1]. The enhanced hydrolysis results in ammonia concentrations in sludge dewatering liquors of >1000 mg N L−1 [1,2]. These liquors can be treated by a follow on deammonification process for ammonia removal. Ammonia and nitrite are converted to nitrogen gas by anaerobic ammonia oxidizing bacteria (AMX) [4]

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