Odour not to be sniffed at
Statutory authorities have to deal with odour complaints from a variety of industries and sectors including the water industry. Nicole Harrison, environmental consultant at Crestwood Environmental, discusses the process
The regulators have a duty under the Environmental Protection Act 1990 (EPA 90) and Environmental Permitting Regulations 2010 (EPR 2010) to investigate cases where odour may be causing statutory nuisance or breaching the conditions of an EPR Permit. Statutory nuisance is defined as ‘any smell arising on industrial or trade or business premises and being prejudicial to health or a nuisance’.
Causing statutory nuisance or a failure to comply with a Permit can result in enforcement action/prosecution and ultimately the closure of site operations. Whilst the closure of a sewage treatment works would be impracticable, a local authority can issue an Abatement Notice under EPA 90, to a water company, to bring about compliance within a given timeframe.
The Environment Agency (EA) can prosecute for any serious breaches of the conditions of an EPR Permit. Therefore, any activities that are potentially odorous should have procedures in place to reduce their risk of causing a statutory nuisance or a breach of a Permit.
Determining whether a nuisance has been caused is difficult and is usually subject to an individual’s perception. Olfactometry is the measurement of the strength and performance of odours.
Crestwood Environmental has been trialling an olfactometer new to the UK, the Nasal Ranger, which provides a confident, scientific method for ambient odour quantification. The Nasal Ranger, which was developed by US company St Croix Sensor, goes beyond traditional estimation methods and has the ability to easily determine ambient odours as a dilution-to-threshold (D/T) ratio at specific locations surrounding or within a waste facility boundary. Rather than a subjective description of odour, the equipment allows the accurate measurement and quantification of the scale of the odour present. There are no laboratory fees associated with the technique, making the innovative odour environmental monitoring time and cost effective.
The olfactometer allows the mixing of odorous ambient air with filtered odour-free air in a controlled volume ratio achieved via two airflow pathways. The odorous ambient air can flow through the orifices in the D/T Dial - located on the end of the device, and the odour-free air enters through multi-media cartridges – located on either side of the device.
The mixed airflows then travel down a barrel and into the user’s nose. The rate at which the recipient must inhale is required to be the factory calibration flow rate of 16-20l/minute.
To ensure this rate is achieved, the measure of the total volume of airflow that is travelling through the barrel is determined and confirmed via a greenlight signal to ensure the correct inhalation rate is achieved. If a red signal is produced the inhalation rate has not been achieved and must be re-tested.
The D/T dial controls the volume of carbon filtered air with the volume of odorous air. Decreasing the filters, using the dial, allows more ambient odorous air to enter the device. The point at which an odour can be detected from the user determines the D/T ratio.
The odour is quantified and a description of the odour is recorded. Quantifying odours can be beneficial for accurate recording and monitoring of daily operations, comparing operating practices, in response/to validate any complaints, following a specific event, monitoring compliance, gathering background information, confirming the effectiveness of odour control measures.
Crestwood Environmental has undertaken odour monitoring surveys at the perimeter of sewage treatment works. The purpose of the monitoring has been to quantify the degree of odour on and surrounding the site from an independent source. The environmental monitoring takes into consideration the meteorological data, including wind direction/speed, relative humidity and barometric pressure, local topography, the GPS locations of each monitoring point and on-site activities at the time of monitoring.
The EA (England and Wales) have a number of instruments and are trialling them for detecting odour intensity; their officers have been trained appropriately and the Nasal Ranger is included in the H4 EA Odour Guidance. One water company in England has a Nasal Ranger and is using it to identify potentially odorous operations.
The use of the Nasal Ranger has proved a useful tool for Crestwood when working with site operators, statutory bodies and neighbours to be able to independently and scientifically quantify and report on the degree of odour arising on and around a site.
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