Monitoring H₂S Levels in Biodigesters

Introduction

The Problem and Its Environmental Impact

Breweries across the United States and around the world are increasingly adopting anaerobic digesters as a sustainable solution for treating their wastewater. The need for this is due to the unique challenges breweries face when dealing with their wastewater. Brewery wastewater contains a range of substances, including sugars, starch, grains, hops, and yeast, that make water treatment difficult for municipal plants. This is in part because these waste products exhibit a high biochemical oxygen demand (BOD), which is the amount of oxygen consumed by organisms as they break down waste.

This elevated BOD is a serious concern since it can lead to oxygen depletion in waterways where the brewery waste is discharged. Improper discharges can cause serious harm to local wildlife. The severity of this problem is highlighted by the fact that the Environmental Protection Agency (EPA) in the United States has filed lawsuits against producers for failing to adequately treat their wastewater discharges.

Anaerobic digesters offer several advantages over other treatment options. These advantages include both smaller reactor sizes and lower initial capital investments. As an added benefit, they also have minimal energy requirements and can produce valuable biogas which can be used for heat or electricity generation. By breaking down the waste substances in the digester prior to discharge, breweries can not only meet environmental regulations, but also generate green and renewable biogas to power their operations.

The Importance of Monitoring H₂S (Hydrogen Sulfide)

Critical to the success of anaerobic digestion is the monitoring of H₂S. H₂S is a gas produced by anaerobic bacteria as they digest wastewater, and even in small doses, it can be extremely toxic. This can pose a significant risk to workplace safety. Another potential problem posed by H₂S, is the generation of corrosive products that can harm the digestor’s construction. In the headspace above the liquid phase of the digester, sulfur-oxidizing bacteria can generate sulfuric acid from H₂S, which can damage the concrete used in the construction of these digesters. Typically, H₂S also needs to be removed from the biogas before it is burned for heat or electrical power as both it and its combustion products are corrosive. Online measurements in any of these applications are extremely helpful to ensure the safe and effective operation of the biodigester.

Applied Analytics OMA-300: A Solution for H₂S Monitoring

Applied Analytics’ OMA-300 process analyzer is an excellent choice for users seeking a hassle-free method of monitoring H₂S levels in their biodigesters. Unlike paper tape analyzers, which rely on reacting toxic lead tape with the process sample to determine concentration, the OMA-300 exposes the sample to ultraviolet light. This allows the analyzer to detect H₂S’ unique absorption fingerprint as well as the amount of H₂S present in the sample. It should not be underestimated how life-changing this feature can be for an operator. Unfortunately, many operators overlook both the cost and regulatory challenges associated with disposing of lead waste.

The OMA-300’s construction also helps to eliminate downtime due to its solid-state design. Unlike traditional paper-tape analyzers which rely on reels of tape that can jam or fail, the OMAs cutting-edge design does not contain moving parts.

As breweries continue to grapple with the environmental and regulatory challenges posed by wastewater treatment, anaerobic digesters, and advanced monitoring tools like the OMA-300 will enable producers to meet their environmental requirements, in a way that is safe, sustainable, and reliable.

Example

Figure 1

Figure 1: OMA-300 UV-Vis Analyzer and sample conditioning system monitoring H₂S in biogas at a brewery water treatment facility

Further Reading