An Analysis of Operation Conditions and Microbial Characteristics in Swine Wastewater Treatment Plants with Spontaneously Enriched Anammox Bacteria

Miyoko Waki,Tomoko Yasuda,Toshimi Matsumoto,Takafumi Nagamine,Yasuyuki Fukumoto,Hirohide Uenishi,Ryu Suto,Chikako Ishimoto

doi:10.3390/pr9061010

Abstract

The spontaneous enrichment of anammox bacteria has been reported in swine wastewater treatment facilities. However, their causative conditions and microbial characteristics, which this study aims to explain, are poorly understood. We discovered eight treatment facilities where the collected red biofilms exhibited high anammox activity levels at 57–843 µmol-N2/g-ignition loss (IL)/h and anammox DNA concentrations of 4.3 × 108–1.6 × 1012 copies/g-IL. The facilities used various wastewater treatment methods—six of them employed a multi-stage continuous reactor, whereas aeration tanks were continuously aerated at another combination of six facilities. Levels of dissolved oxygen (DO) in these tanks were fairly low at ≤1 mg/L. Pyrosequencing of the biofilms indicated the presence of 3–62.5% Planctomycetes, and the dominant anammox in each biofilm comprised three operational taxonomic units (OTUs) similar to Candidatus Jettenia asiatica, Ca. Brocadia fulgida, and Ca. B. caroliniensis. This suggested that some particular species of anammox bacteria naturally thrive when operating a swine wastewater treatment facility at low DO levels. The frequent enrichment of anammox biofilms at the sampled sites indicated that these treatment facilities were good seed sources of anammox; therefore, anammox treatment would be a viable method for the removal of nitrogen from swine wastewater.

Highlights

Nitrogen (N) pollution in water systems due to livestock excrement has become a serious problem owing to the worldwide increase in livestock populations [1]
These results showed that red biofilms contained high concentrations of living anammox bacteria
Enriched anammox biofilms were found in conventional activatedsludge facilities at eight swine farms in Japan

Summary

Introduction

Nitrogen (N) pollution in water systems due to livestock excrement has become a serious problem owing to the worldwide increase in livestock populations [1]. In Japan, pig farming, in particular, generates a large amount of wastewater containing nitrogen; an appropriate treatment method is required. The activated-sludge process is the most widely used method for wastewater treatment in swine farms in Japan. Untreated swine wastewater is a mixture of urine, feces, and service water; this is first pre-treated by removing suspended solids using screens, gravity sedimentation, or mechanical separation with chemicals, and treated with the activated-sludge process. Various activatedsludge processes, such as a sequencing batch reactor and a single or multi-stage continuous reactor with or without a membrane, are employed. Nitrogen removal by the conventional process in the swine wastewater treatment process is limited; using anaerobic ammonium oxidation (anammox) technology for nitrogen removal is desirable

Objectives

Methods

Results

Conclusion