To manage effluent treatment costs, you must first understand the makeup of your effluent stream, and how it’s influenced by your production activities. Effluent treatment broadly falls into three categories:
A company’s chosen treatment route depends on several factors, eg the volume and characteristics of effluent, space available on site, and available treatment capacity at the local municipal waste water treatment works. There are financial and operational considerations for each.
A company may not be able to obtain the consent conditions it desires for discharge to sewer, and so may need to pre-treat to a standard that enables it to comply with the consent conditions, or re-examine its production plans.
For instance, dairies and breweries, due to the biological strength and volume of their effluent, are typically unable to discharge direct to sewer without some pre-treatment.
Selecting the most appropriate technology with the right capacity to meet treatment needs seems obvious advice. Yet, many get this wrong and end up with high operating costs and a problematic plant; a greater problem than the one they were trying to solve! So, before committing to a treatment route, do the groundwork, really understand your requirements. Simply screening or balancing or removing solids could be sufficient.
Once you’ve eliminated equipment failure, check for changes to effluent volume/characteristics, or changes in temperature. New shift patterns or a transient workforce, unreported spillages, changed production methods/cleaning agents can all affect the waste.
A jam producer who starts producing pickles will generate a more acidic effluent, for instance, which could negatively affect the treatment process.
A sudden increase in production, such as in seasonal businesses, can create treatment problems if unplanned. The answer may be installing temporary treatment capacity during busy periods – there can be problems in ‘underloading’ in ‘off peak’ periods. This can be prevented through a modular plant design, with treatment stages brought online or offline, or by the plant being artificially fed during the off-peak season.
For example, a low volume concentrate waste, normally disposed of by tanker, being fed to the plant at a controlled rate.
Mogden charges can range from £450 per year to a six-figure sum in the UK. The charges are calculated by a formula:
The elements are weighted. By using the formula, and associated tariffs applicable to the local water company, along with information from effluent monitoring at site, a view can be taken on where savings can be found.
For example, a 40% reduction in trade effluent charges may be possible by reducing suspended solids by 85% and COD by 50%. However, don’t forget to factor in the cost of achieving this reduction.
Some reduction might be achieved by switching your product strategy away from one that makes a disproportionate contribution to your Mogden charge. Equally, when assessing new product lines, weigh up the effect on effluent volume and characteristics.
In essence, understand the close interplay between effluent streams and production profitability, and cost savings will follow.
Clwyd Jones works for SPS, which provides process solutions for ageing or under-capacity treatment plants, peak season surges and a reduction in Mogden charges.
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