Where does your water go?
All the water which comes into your workplace will eventually find its way back out into the environment. Along the way, your company will either deliberately load it with contaminants and use it as a transportation medium or, possibly, contaminate it accidentally.
It is then discharged to either controlled waters or to the sewerage system.
Mass balance exercises are also useful in predicting the quantity of water flowing through your site and its processes.
A company can choose to carry out some treatment process to remove contaminants from surface water drainage or foul water before discharge.
You will need to understand where your waste water goes and check that the connections go where you think they do. This will involve examining drainage plans and looking at the drains themselves to verify those plans.
In poorly mapped or highly modified systems, specialised surveys using such techniques as closed circuit television (CCTV) may be appropriate.
What contamination are you likely to add?
As well as the destination of your waste water and its quantity, you will also need to know what materials are flowing with it. When assessing your potential emissions, both accidental and deliberate, the following need to be considered:
- What materials do you have in storage? Surface water drains are vulnerable to pollution. Spillages and leaks from tanks and drums are a major cause of substances entering these drains, which run untreated into surface waters.
- What materials can be released into your surface water drains? Run off can pick up substances, such as powder, zinc from roofing or other contamination, on the way to surface waters. Activities in yards and car parks can release contamination (see below).
- What potentially polluting activities happen in your yard or car park? Water from washing equipment, vehicles, plant, yards etc is all effluent and should not be allowed to run into surface water, onto open ground or even to sewer, unless consented, e.g. using detergents can emulsify oils which can then flow freely through interceptors.
- If there is a fire, where will the fire fighting water go and what will it contain? A fire can result in all manner of chemicals being washed into foul and surface water drains, and even to groundwater. The Environment Agency is concerned about fire brigades washing contamination into local drains and waters.
It is possible that you could find the difficulty of dealing with a fire compounded by a prosecution under the Water Resources Act 1991. If the receiving waters fed by your site drainage are at risk, you should consider diverting the flow to some impoundment if possible.
Your interaction with the sewerage undertaker
Your company’s interaction with the sewerage undertaker is part commercial and part regulatory. You will reach a commercial agreement with them to take away and treat your wastewater. Their inspectors will come on your site to take samples of the waste water and ensure ongoing compliance. If you breach the conditions of your consent, they can prosecute you.
Saving water – minimising waste
As with any other waste, the most environmentally-friendly and economically viable option is to ensure that as little water as possible is used. Less water usage results in a reduced wastewater discharge.
The following is an action plan for saving on water usage, wastage and discharges:
- Introduce simple minimisation measures such as flow restrictors, hose pipe automatic cut off valves, or triggers, etc. – these can all help to ensure that water is used effectively and not wasted.
- Redesign processes where possible to make the best use of water, e.g. redesigning spray bars in a machine where components are rinsed clean.
- Fit spray taps, reduced flow and timed flow taps, as well as timed flow urinals and dual flow toilets, to reduce ‘domestic’ water consumption.
- It is also important to make people aware of the need to report leaks and failures in control systems to help assist the company manage water consumption.
- Put spill prevention procedures in place and carry out regular drills. Preventing spills will prevent sudden unplanned waste water discharges.
- Plan for other emergencies, for example, preventing hose water entering the nearby watercourse in the case of a fire (see Envirowise)
Pre-treatment
Treating wastewater before it leaves your site may be of benefit for discharges to surface water and to foul sewer. Here are some examples of treatment processes:
- Physical/chemical procedures such as sedimentation, precipitation, flocculation, interceptors, neutralisation, oxidation/reduction, electrolysis, ion exchange can be used to separate and remove various soluble and non-soluble contaminants
- Reverse Osmosis can be used to separate oil/water emulsions, for example, machinery coolant. The emulsion is passed along a plastic pipe containing a porous membrane inner tube. Water molecules are able to pass through the pores of the membrane, but the oil molecules are too large.
- Biological treatment, similar to aerobic sewage farms or anaerobic culture systems, can only be used for removal of organic substances – it is used in the chemical and pharmaceutical industries.