Frequently Asked Questions

What applications can the Sand Lane Recovery System be used for?
Dewatering and rinsing of sand from sand lanes or other sources. The system removes the residual slurry liquor containing most of the organic matter and bacteria allowing the early re-use of the sand.

Can I use the Sand Lane Recovery system to directly recover sand from slurry?
Unfortunately not, the system is only designed to dewater and rinse sand once it has been separated from the slurry.

How does the Sand Lane Separation System work?
Sand recovered from the sand lane is loaded into a hopper from where it is fed via a variable speed auger onto a vibrating screen. The motion of the screen removes most of the slurry liquor which passes through the screen deck into the sump below. The sand is retained on the dewatering deck and can optionally be rinsed with clean water and/or biocide solution.

What is the typical moisture content of the recovered sand?
This varies depends on the particle size distribution of the sand. The finer the sand the higher the retained moisture content.

How quickly can I re-use the sand?
This depends on advice from you vet/ animal hygiene specialist. By using a combination of clean rinse water and/or biocide the sand should be sufficiently sterile for immediate use. However, it might still be necessary to stockpile it for a short while to allow the drainage of the residual free liquid. Without the use of rinse water and/or biocide it may be advisable to windrow the sand for a longer period to allow drainage and breakdown of the small amount of residual organic matter.

What routine maintenance is required?
The only routine maintenance required is the regular greasing of pumps/motors in accordance with the manufacturer’s recommendations.

What wear parts are there?
The sand feed auger will be subject to wear – on other applications this has needed to be replaced every 5 years or so. Alternatively, the auger can be fitted (at extra cost) with replaceable polyurethane wear shoes. The pumps are rubber lined minerals industry units specifically designed for pumping sand slurries. These give a much longer life than conventional pumps. The screen decks are made from poly urethane to give a long life.

What applications can a rundown screen be used for?
Separation of coarse fibre/debris from dilute slurry

Can I use a Rundown Screen to separate fibre from undiluted Slurry?
Unfortunately not, as the undiluted slurry is too viscous/thick to allow separation.

How does the Screen work?
As the dilute slurry flows down the face of the screen, the liquid together with most of the fine organic matter and sand passes through the screen into a collection sump. The captured coarse organic matter is moved down the screen by dilute slurry and is further dewatered using an optional roll press.

What is the typical solids/moisture content of the separated fibre?
This varies with the consistency of the fibre being separated and the degree of dilution. Typical values are 20% to 30% solids i.e. water content of 70% to 80%.

What is the screen made from?
The screen is made from stainless steel wedge wire bars. We use wedge wire rather than perforated plate as it is stronger and the shape of the bars help to reduce clogging.

What size screen openings are available?
Wedge wire screens are available in a range of openings typically from 0.25mm up to 3mm. Importantly because of the screen inclination, the apparent opening is approximately 50% of the actual opening. For example, a 3mm wedge wire screen has an effective separation size of 1.5mm.

How is the screen sized?
As the material to be separated varies between applications, wedge-wire screens are sized on their clean water capacity. This is then downrated depending on the nature of the slurry to be separated.

What routine maintenance is required?
The screen needs to be pressure washed at least daily to remove trapped fibre particles. During periods of hot weather, the screen may need to pressure washed more frequency to prevent the organic matter “baking” on. Alternatively, an automatic wash systems can be provided at an additional cost.

What wear parts are there?
As there are no moving parts on the screen itself and there should be little wear of the wedge wire. There will however be some wear on the roll press, which, depending on the application, may require replacing every one to two years.

Why is nutrient removal/control becoming increasingly important?
Recently published studies show agriculture accounts for 40% water pollution in the UK.  In comparison sewage pollution now accounts for 32%

What contaminants are most important?
The principal pollutants of concern are Nitrogen (in the form of ammonium), phosphorous and potassium.  Over application of these in the form of either slurry/manure or artificial fertiliser has led to the build-up of excess concentrations in the soil.   These then seep into the watercourse with rainfall runoff.

Other principal contaminants of concern are Biological Oxygen demand (BOD) and chemical oxygen demand (COD) due to the particulate and dissolved organic matter in the slurry.  This forms a food source for waterborne bacteria which consume the available oxygen in the water to the detriment of aquatic life.  Typical BOD values are:

Source: Reading University

The BOD loading in a 500 head herd is roughly equivalent to a small town with a population of around 5000 people.

How much nutrient does a conventional separator remove?
A conventional fibre separator (such as a screw press) only removes a small proportion of the nutrients as most of the nutrients are either in the form of very fine (colloidal) solids or dissolved in the slurry liquor.  Use of a centrifuge increases recovery but still leaves a significant proportion of the nutrient in the slurry liquor.

So how can the nutrients be removed?
These can be removed by adding chemicals to precipitate and/or combine the nutrient into solids which can then be physically separated from the slurry liquor.  This results in a slightly coloured liquid low in solids and nutrients- commonly referred to as “Tea Water”

Is it possible to get the water recovered from the slurry clean enough to discharge to surface water?
Yes, but this requires additional process stages.   After removing most of the nutrients the slurry liquor still contains other contaminants which are harmful to the environment (for example BOD/COD, ammonia, etc.).    Additional treatment stages would be required to remove these to level acceptable for discharge.

Would I need a permit to discharge the water recovered from slurry?
Yes, you need a permit from EA/SEPA/NRW to discharge any treated water to a surface water course or a Trade Effluent Consent to discharge it sewer.  The permit would stipulate the required water quality – which for discharge to surface water depends on the size and characteristics of the receiving watercourse.

Is it possible to get the water derived from the slurry clean enough for re-use?
It is possible to get the water clean enough for re-use but at a cost.  Typically, this involved multiple treatment stages culminating in use of membrane filtration/ Reverse Osmosis. A process that would allow recovery of a proportion (but not all the liquor as water for re-use).

Is there a one size fits all solution to nutrient removal?
Not really as each farm has its own unique challenges.  Our approach is to work with each farmer to develop a bespoke solution to each problem.  That way we can achieve the required water quality without incurring excessive cost.

Can the additional treatment stages be added at a later date?
Yes, as the nutrient removal/water recycling involves a number of separate process stages it is possible to add these at a later date to further improve the treated water quality.