Reducing Water Use & Effluent In The Furniture Industry

Last updated: (February 2005)

Introduction

Furniture manufacturing sites use water in various processes as well as generating a variety of effluents. This Reference Note provides a summary of relevant legislation and best practice in water usage and the treatment of waste waters.

Background

Sites involved in the manufacture of furniture will frequently not realise the importance of water usage and effluent disposal within their operations. However, a wide variety of processes consume water and generate effluent.

Potential uses for water include:

• domestic services such as toilets and drinking water
• water back booths used for trapping wood coating over spray
• cleaning of water based spray lines and veneer presses
• vehicle washing
• water based metal degreasing plants
• cooling for solvent based metal degreasing plants

• boiler blowdown - excess liquid from water based heating systems which contains corrosion inhibitors
• compressor condensate – an oil/water mixture produced by air compressors

Compared to many raw materials, water is only a small cost for most furniture manufacturing sites. However, when all related costs associated with water use are added into the equation, a significant sum may be involved. Costs may be incurred through:

• purchase of fresh water
• pumping costs on site
• capital costs – of pumps, pipes and tanks
• maintenance costs
• treatment costs
• disposal of used water

Legislation

The Water Resources Act is designed to protect "controlled waters". These include rivers, streams, ditches, ponds, territorial waters (within 3 miles of national boundary) and groundwater. Surface water drains are used to discharge rainwater from sites into controlled waters (including to groundwater via soakaway).

Consequently, such drains are an important pathway for carrying spillages into controlled waters. These discharges receive no form of treatment (as they would from a sewage treatment works via foul sewer) and as a result many major pollution incidents occur from pollutants travelling down surface water drains each year. Such pollution will normally constitute a breach of Section 85 of the Act, under which it is an offence to "cause or knowingly permit any poisonous, noxious or polluting matter, or any solid waste to enter controlled waters".

In effect, this legislation makes it an offence to discharge anything other than rainwater into surface water drains and controlled waters without a consent from the regulator, eg the Environment Agency in England and Wales. Frequent areas of contravention include veneer press washdown effluent, air compressor condensate, vehicle washdown water, spillages and loose sawdust washed into drains by rain water.

Scotland

The Water Resources Act 1991 does not apply in Scotland. Instead, water controls are provided by the Control of Pollution Act 1974 and the Water Act 1989 as amended by the Environment Act 1995. In reality, although the names are different, the requirements are similar. For example, the main offences under the WRA are contained in s85 and these are mirrored by s30F of COPA.

Water Industry Act 1991

Many furniture manufacturers will produce "trade effluent". This is defined as "any liquid, either with or without suspended particles, which is wholly or partly produced in the course of any trade or industry carried on at trade premises". It includes liquids such as:

• boiler blowdown
• compressor condensate
• vehicle washdown
• veneer press wash down water
• water back booth effluent

Under the Water Industry Act, companies wishing to discharge trade effluent to foul sewer must hold a consent from the local sewerage undertaker. Charges may be levied according to effluent nature, concentration and volume.

The Water Industry Act 1991 does not apply in Scotland. Foul sewer controls are provided by the Water (Scotland) Act 1980 as amended by the Water Act 1989. Sewerage and drainage services are covered by the Sewerage (Scotland) Act 1958.

Environment Act 1995 - Contaminated Land Provisions

The contaminated land provisions of the Environment Act are expected to take effect during 2000. They will place a duty upon regulators to cause their area to be inspected from time to time for the purpose of identifying contaminated land. Where contamination is identified, clean up will have to be undertaken by the "appropriate person" to a level that is suitable for the current or intended use.

Water Usage

This section provides some common sense advice to reduce the cost and environmental impact of water usage.

General

• The measurement of water usage is essential to highlight trends, abnormalities, the potential for savings and the effect of water minimisation measures.
• Consider the use of a systematic water minimisation programme along the lines of that outlined in various ETBPP documents.
• Monitor usage over time to detect any leaks. These will show up as rising consumption at times when it would not be expected.
• Check water meters during down-time, eg shutdown or the end of a shift. Usage will generally be minimal in a furniture factory, unless there is a leak or appliances have been left running.
• Leaks can arise from damaged pipeline connections, worn valves, flooded floats on water tanks and corroded pipe work.
• Consider the inclusion of water minimisation issues within other training programmes.

• Ensure taps are not left running/dripping. A dripping tap can lead to an annual loss of 9,500 litres – around ?13 worth.
• Consider fitting percussion (push) taps on all washbasins – these can lead to a 50% reduction in water usage
• Implement controls in toilet areas - such as the prevention of unnecessary urinal flushing via controls. Passive infrared flush controls can lead to a 70% reduction in water. Reducing the capacity of each flush in a WC via a "hippo", brick or other cistern volume adjuster can save 16%.
• One furniture manufacturer fitted urinal controls at around ?60 per washroom. These resulted in a 46% saving in water consumption!

• Eliminate unnecessary washdowns
• If water is used for washing, can it be circulated a number of times - eg using "dirty" water as a pre-wash?
• Some companies utilise water back booth filtration systems which remove solids from the effluent. As a result, booth effluent only needs to be tankered away twice per year rather than once per quarter.
• Sewage is normally charged on the basis of a percentage of the clean water delivered to the site. If a significant amount of your company water consumption is due to water back booths, such liquid will be tankered off site rather than going down the drains. Therefore check your water bill to see the estimated percentage of water delivered that is charged as sewage out. If this is too high, contact the sewerage provider.
• Where water is used in condensers to cool solvent-based metal degreasing plants, attention should be paid to the siting of the degreaser, water pipes and water storage tank. The closer this equipment is to sources of heat (eg process machinery) the more water and energy will be required for cooling.
• Open loop water cooling is sometimes employed using a constant stream of fresh water. Consideration should be given to closing this loop with the use of a water tank and cooling tower.

Effluent Disposal

Many air compressors produce an oil/water mixture known as condensate. All too often this is discharged to surface water drain or direct to ground through a pipe running through the compressor house wall.

Condensate is a trade effluent and there are a variety of options for dealing with it. Oil/water separators can be fitted to the compressor and these will draw off the oil allowing it to be sent for recycling. Alternatively, condensate may be discharged to foul sewer under consent from the sewerage undertaker. Some sites prefer to collect condensate in drums and dispose of them via a registered waste contractor.

Boiler blowdown
Certain heating systems use water filled pipes which are dosed with corrosion inhibitors. These may discharge liquid or blowdown on a regular basis. Depending on the nature and concentration of the chemicals, blowdown may be classifiable as special waste or may be suitable for discharge to foul sewer under consent.

Vehicle washing
It is often assumed that vehicle washing is not a source of environmental concern as so many vehicles are washed in a domestic environment. However, lorry washing on site will generate a trade effluent containing detergent or cleaning solvent, oil and solids which will typically discharge to surface water drains or direct into the ground.

Such discharges require a consent – and regulators such as the Environment Agency prefer that the drains from the washing area are diverted to foul sewer under consent from the sewerage undertaker. Where this is not possible, washing should occur off-site at a specialist facility.

Veneer press washdown
Urea formaldehyde based glue is normally used to bond veneer to board material. Most glue spreaders require regular cleaning to prevent a build up of adhesive. Water is normally used for cleaning and effluent will be generated as a result.

This effluent will contain urea, formaldehyde and particulates. The preferred disposal route will depend on the quantity and concentration. Surplus glue that can be scraped off a veneer press can be left to set hard enabling it to be disposed of as general waste.

The greater the water content, the lower the chances of washdown water setting. Some companies place the effluent into a settling chamber allowing the solids to be segregated, dried and hardened. The liquid effluent can then be disposed of to foul sewer under consent. Others discharge the effluent straight from the veneer press into the foul sewer under consent. However, this may lead to pipe clogging, depending on the nature of the washdown.

Water back booth effluent
Some wood coating operations use water back booths for trapping overspray. Booths hold a fixed quantity of water which is pumped to the top of the booth and released along its length to form a water curtain, through which air is extracted. The liquid will collect particulate matter and solvents – though the latter will evaporate off if they are not water soluble.

Booths require treatment for pH and to prevent legionnaires’ disease. Particulate matter will generally be removed by dosing with chemicals which make the solid matter float or sink. Depending on the rate of booth usage, the water may need changing every quarter. Tankers are generally used in this case.

Some companies utilise water back booth filtration systems which remove solids from the effluent. As a result, booth effluent only needs to be tankered away twice per year rather than once per quarter.

Certain companies also use the booth effluent as a method of disposing of waste thinners and surplus coatings. This is not advisable as it will increase the toxicity of the effluent and could lead to it being classified as special waste. In addition, solvent which is tipped into the effluent cannot be reused or sent for recovery.

The Future

The EU Landfill Directive may affect the disposal of certain liquid wastes such as water back booth effluent. From 2001 the disposal of non-special liquid wastes will not be allowed in new landfill sites and it will have to be phased out at existing sites by 2009.