Effluent Monitoring and Targeting

A major overhead for any processing plant is effluent discharge. In accordance with the water industry act 1991, any company having significant quantity of trade effluent must obtain consent prior to making a discharge to the public sewer network or to a water course.

Effluent Monitoring and Sampling

Responding to today’s industry requirements, businesses are starting to focus on the need for not just automated sampling and effluent monitoring, but for complete engineered solutions including the use of monitoring and targeting systems to control costs and remain within consent. Helen Dennen, Analytical Product Specialist at Endress+Hauser Ltd, discusses the importance of employing accurate and reliable methods of sampling and analysis, as well as monitoring and controlling systems to ensure efficient plant operation and cost savings.

The self-monitoring obligation

More stringent regulations and consent requirements are continually being put in place to maximise compliance by industrial companies, and minimise harmful discharges to the environment. The typical consent parameters include pH, temperature, organic load, suspended solids and ammonia, and breach of the consent limits can prove costly to offending companies.

Companies whose processes have a high pollution potential are also governed by Environmental Permitting Regulations (EPR). Previously recognised as the Integrated Pollution Prevention and Control (IPPC) directive, they are policed by the Environment Agency (EA) and Scottish Environment Protection Agency (SEPA). They are designed to prevent, reduce and eliminate pollution at source, and to ensure compliance with the legislation, operators must use Best Available Techniques to prevent emissions. Where that is not possible, they must reduce them to an acceptable level.

Further legislation came into force on March 1^st 2009. The Environmental Liability Directive adopts the ‘polluter pays’ principle, aiming to hold those responsible for causing damage liable for remedying it. Additionally, those who have caused threat of damage will be responsible for taking preventative steps to avoid future damage.

All of these obligations make the need for accurate sampling and monitoring a vital necessity.

On-site Effluent Sampling

On-site effluent sampling is a widely used method of obtaining accurate samples and monitoring effluent discharges. In the absence of representative sampling, the trade effluent officer will simply take a sample of the effluent when on site – however, if this is a high load period, such as after a plant wash down, the effluent billing could be incorrectly inflated. On site samplers enable fully automated sampling, defined distribution and thermostatic storage of effluent.

The sampler positioning and set up are vital in ensuring that the samples obtained are representative of the effluent profile. Whether sampling is based on time, flow or quantity is dictated by the process and/ or regulatory requirements. For example, in applications such as batch processes the flow will vary according to production schedules.

Sampling techniques

Furthermore, the sample distribution can also be configured as required. Simple composite sampling involves gathering the samples in a single container and balancing out high and low load periods to give an overall limit upon which correct charges can be made. For a complete picture of the load profile, a sample distribution, for example 24x1 litre bottles, enables accurate identification of the peak load periods. Understanding these periods can help in highlighting problem areas and enable measures to be put in place.

Continuous Monitoring

In addition to basic sampling, effective monitoring of the effluent can be carried out by automated measurement stations. Continuous monitoring offers significant advantages over the ‘grab sample’ technique using laboratory analysis - real time monitoring of consented parameters such as pH and COD enable swift action to be taken in the event of an incident - whereas if monitoring by grab sample, the effluent has already gone to drain by the time any issue has been identified.

Continuous real-time monitoring reveals missed information when relying on grab samples.

Automated Monitoring & Targeting: a vital business investment

It is clear that investment in accurate and reliable monitoring equipment can help in optimising effluent treatment processes and minimise product losses. Monitoring and targeting (M&T) is a mechanism for controlling energy consumption and cost. A useful M&T system can be extremely simple and applied effectively to effluent monitoring.

By importing flow and analysis data into the system along with consent information, trade effluent charges can be defined, recorded and reported. Additionally, reporting frequency can be set on an hourly basis to quickly highlight potential problem areas, enabling measures to be put in place to quickly and effectively remedy them. Consequently the effluent treatment process is optimised and facilitates significant cost reductions - a major consideration in the current climate.

It becomes apparent that the selection of the appropriate sampling method and energy monitoring system go hand in hand when it comes to effective and cost-effective effluent monitoring and treatment. In order to achieve efficient wastewater monitoring processes and return on investment, businesses need to make a vital step further to more all-round solutions that cover not only analytical instrumentation but also contribute to business performance.