Managing trade effluent

No good comes from failing to control the bad stuff; many companies are unaware of the environmental damage and big fines they will face if site effluent is not disposed of appropriately.

In this article, Dave Walker, commercial director at Detectronic, and with over 25 years’ experience in trade effluent management, offers some advice on understanding what your site is discharging and keeping on the right side of the law.

It’s easy to see how trade effluent could fall down the list of priorities when you are managing a busy food or drink processing site. However, failing to stay within the limits of your agreed trade effluent consent could land you in deep water with expensive environmental clean-up costs and fines in excess of £40,000.

The good news is that once you understand the rules and what your consent levels are, it’s fairly straightforward to keep on top of it.

So, what is Trade Effluent?

“Trade Effluent is any liquid waste, other than surface water and domestic sewage that is discharged in a public sewer”. Sites within the food and drink sector may have fats, oils and grease, chemicals, detergents, solids, heavy metal rinses or food wastes contaminating their waste water.

A consent agreement between the discharger and sewage undertaker determines the volume and concentration of materials a company is allowed to release into the waste water discharge stream. Detectronic works with companies to keep them compliant by introducing measures to monitor and manage trade effluent and water consumption more efficiently and often saving them money too.

Our range of sensors and instrumentation can monitor flows of water, waste water, surface water and water quality composition. The ORAKEL System can monitor parameters including but not limited to organics, suspended solids, pH,  chlorine and metals.

Recently,by helping a processing plant take control of its waste water and reduce the strength of its effluent produced following repeated breaches of their consent, the company is benefiting from annual savings in excess of £110,533 per year.

To maintain these savings and ensure continuous environmental compliance, sensors are to be installed which will monitor and trigger basic screening of the processes waste carryover “raw material”. In addition to the sensor technology being deployed, a simple balancing tank arrangement will also be put in place and used to hold back higher strength liquors before releasing them back into the final effluent stream when concentrations have fallen below a safe level. By understanding the complex effluent streams on site, working with production managers and segregating the waste in this way, spikes in the combined oxygen demand (COD) are easily removed in a cost efficient way producing a more polished trade effluent for final discharge. (See Fig 1).

Releasing harmful waste doesn’t just affect the environment; it damages reputations and results in severe penalties, which are ever increasing. Don’t let the next big fine be yours. It takes just a few simple steps to take control of your trade effluent.

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Fig 1

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Fig1 left

When the COD goes above T1 Trigger level, the trade effluent stream is screened and passed through a final polishing stage.

In this example, removing the spikes reduced the daily load from 1696 Kg/day to 1187 Kg/d and introduced a saving for the company in excess of £110,533 per year.

NB: in certain processes, simple periodic averaging of the specific individual trade effluent load can also reduce the overall daily Load Kg/d without the need for additional treatment.

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NOTE: For client security the data used in this article has been changed for illustrative purpose only. In the illustration above, annual trade effluent before removing the COD spikes was calculated at £495,553 per year.

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Fig2

C= (R + V + B1) + (B2 x Ot/Os) + (S x St/Ss)
C = Unit Charge calculated £/M3
R = Receive and Convey Sewage charge
V = Primary Treatment charge
B = Biological treatment charge
S = Sewage sludge charge
Ot = Chemical Oxygen Demand (COD) in mg/l of trade effluent after 1 hr quiescent settlement at pH 7
Os = Chemical Oxygen Demand (COD) in mg/l of average strength sewage
St = suspended solids in mg/l of trade effluent at pH 7
Ss = suspended solids of average strength sewage

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Fig2 left

The Mogden Formula used to calculate the annual cost of effluent discharged.

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