Answer by Tommy Butler, Butler Manufacturing Services Ltd.
If grease in excess of 50 mg/l is contained in the sewage stream, it will negatively affect the performance of your sewage treatment plant, regardless of the technology because the vast majority of sewage treatment plants are based on a combination of settlement/biological treatment, where a biofilm (bacteria and other microorganisms) consumes the biological content of the sewage in combination with settlement e.g. BOD and make it safe for discharge.
Grease more correctly referred to as Fats, Oil and Grease or ‘FOG’ for short is very difficult to break down and does not settle out well. FOG will coat the biofilm making it impossible for the biofilm to access the oxygen it needs to breath. Therefore, as the level of FOG in the sewage increases the growth and performance of the biofilm is negatively affected, eventually to the point where no biofilm can survive and there is little or no sewage treatment. High levels of grease will also be contained in the effluent further increasing the BOD/SS content. No to mention the pungent smell of high level of rancid grease!
This is why all premises with commercial cooking on site must have properly sized and maintained grease traps installed. The first part being that the grease trap(s) remove FOG to a level of 10 mg/l and the second that they are regularly inspected and emptied as soon as they are full. If there is more than one kitchen on the site each should have its own grease trap.
BMS, in our 36 years of business, have come across countless situations where either no grease traps or inadequate grease traps are installed and secondly even if the correct grease traps are installed, that they are not regularly inspected and emptied.
Not only does FOG have consequences for a Sewage Treatment System but it will also progressively block pipes forming ‘Fatbergs’, which will eventually mean expensive professional cleaning of the sewage pipes is required. For this reason, it is recommended that everyone including residents in private accommodation do not put FOG straight down the drain!
Example of a Giant Fatberg blocking a pipe
The good news is that BMS have substantially improved the performance of many sewage treatment systems by installing properly sized grease traps (if not already in place) and working with the owners to ensure a proper maintenance regimen is in place. As part of our sewage treatment solution BMS manufacture static grease traps to European EN1825 Standard.
A lot of people view removing grease as dead money but not doing so as described above is not only illegal but will have a lot of negative consequences. Indeed, a lot of commercial establishments have been fined and even threatened with closure due to their poor grease trapping regimen.
Typical biofilm surface with high inlet Fats, Oil and Grease (note the grey greasy appearance with the absence of a biofilm compared to the healthy surface below)
BMS Rotor with healthy growth at large Irish Hotel after properly sized and maintained grease trap is resolved.
The use of heavy degreasers, enzymes and heating elements, in our experience causes more harm than good, as it typically only pushes the problem further down the pipes or indeed, into the sewage treatment plant, again with all the negative consequences as described above.
If there is a FOG problem at a site, the solving of this problem will definitely improve the performance of your sewage treatment plant, sometimes substantially.
Finally, if you need a sewage treatment solution for your hotel, restaurant, pub or tourist site, we have 36+ years’ experience producing effluent to the highest standards available worldwide e.g. BOD/SS < 5 mg/l, NH4 < 5 mg/l, TN < 10 mg/l & P < 1 mg/l. However, one of the first places we will start is checking what grease trapping you have in place and what maintenance is being done!
BMS GT08 Grease Trap in operation at a large Irish Hotel with high function/wedding business (note the large amount of FOG trapped). This is installed adjacent to the kitchen before entering the sewage stream. The installation of this grease trap immediately solved a large grease problem at the BMS Blivet sewage treatment plant. Please note that this is only maintained when the grease trap is checked regularly.
About BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with a lot of expertise in wastewater and stormwater.
BMS manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks/filters & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more.
Design Services offered by the BMS
BMS have over 35 years’ experience in sewage, wastewater and surface water design
BMS can design your sewage, wastewater or surface water management system for you from the ground up.
- BMS can design a customised sewage treatment system specifically for each project. BMS will produce a detailed process description including design calculations and drawings for approval.
- BMS can design your full surface water management or SuDS system from first principles.
- BMS have invested in specialist software, which produces comprehensive design data. The design will include a full proposal, drawings and design calculations.
- BMS can offer advice on sizing/selecting the correct attenuation/infiltration system, petrol/oil interceptor (separator), vortex silt/oil/debris defender, outlet flow controls & storage tanks.
- BMS uniquely offer a ‘one stop shop’ from design to installation for our surface water management products.
- All products are ISO 9001:2015 Quality manufactured in Ireland and Europe.
- BMS offer free Continuing Professional Development (CPD) Seminars on Sewage Treatment and Surface Water Management both virtually or in person.
- BMS can design a custom pump station solution for your requirements in GRP/FRP. This can include emergency storage and valve chambers and are normally delivered ‘ready to go’.
- BMS can design a vehicle wash water recycling system for you with 100% Recycle and Zero Discharge.
The question above was an interesting one we received from a French customer this week. A lot of sewage treatment plants are installed in the lowest area of a site to try and achieve gravity flow into it. However, with more intense rainfall becoming the norm, low lying areas can often be prone to surface flooding. Sometimes large areas of sites can be subject to flash flooding and ponding.
The good news is Butler Manufacturing Services can offer a number of different solutions:
1. If the installation location is subject to flash flooding you can install our market leading Blivet Sewage Treatment Plant completely above ground and then pump the sewage up to it. The top of the Blivet is 2.3 m above ground so as long as the inlet and outlet pipes are water tight, this solution along with anchoring to a concrete slab and water tight electrical conduits, will ensure continuous sewage treatment even during flooding. Of course the only down side is that sewage needs to be pumped to the treatment plant. You can see a good example below of a plant installed with anchoring to resist seasonal/flash flooding.
2. In the above case floodwaters can rise to 2.5 m, so we recommended to the customer that the Blivet is installed on a 0.5 m raised slab, meaning the Blivet will be above the max flood level with an extra 200 mm safety margin.
3. For a lower lying area with some ponding, BMS can work with you to install a surface water drainage solution around the plant, to make sure that no flood water enters the plant, drawn from our complete one stop shop for surface water management.
4. Another solution is to install our Blivet Sewage Treatment System in a concrete basin with a prefabricated shed above it and some surface water management.
We cannot say we have seen every scenario but having manufactured sewage treatment plants since 1986, which have been exported to 50+ countries, so we have seen a lot and have had to come with up some very innovative solutions.
If you have sewage treatment project with an installation prone to ponding/flooding or any other sewage treatment project, please contact BMS on +353433326100 or email: [email protected] or log on to www.butlerms.com
Example of BMS Blivet Sewage Treatment Plant installed above ground with anchors to mitigate against intermittent site flooding.
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location.
Answer
Thank you for your question. The level of maintenance required after installing a surface water attenuation, infiltration or SuDS system is a very hot topic especially when the local municipal authority will be taking the area in charge and will have to look after maintenance in the future. Naturally as budgets at local level are stretched the last thing local authorities want to do is commit funds to ongoing maintenance.
The good news is that BMS have pioneered two different ways to make an attenuation, infiltration or SuDS system essentially maintenance free.
How do we make BMS Drainmax Tunnels Maintenance Free?
With our Drainmax Tunnel attenuation/infiltration system we recommend the installation of an isolator row. The row is completely surrounded by a permeable geotextile with a MacTex liner at the base. The Drainmax comes with 52 slotted holes per tunnel which allow the water to infiltrate out into the rest of the tunnels in an installation. However, all solids are contained within the isolator row, which means maintenance is confined to this row. The MacTex liner allows jet washing of the isolator row and means all solids can be washed through to the outlet manhole if required. However, if an isolator row is combined with a BMS Petrol/Oil Interceptor up stream and a BMS Stormbreaker Defender vortex silt/oil/debris downstream of the isolator row then maintenance is virtually eliminated bar emptying the interceptor and Defender when full.
You can see examples of systems on the next page, furthermore you can watch a video on the Drainmax below
How do we make BMS Stormbreaker System Maintenance Free?
Our Stormbreaker Attenuation/Infiltration system is a class leading Irish designed and manufactured Agrément certified system that is exceptionally strong and can take huge loads and is also very easy to transport/install. As it is a crate like system, we have devised a different way to prevent solids getting into the system.
We start off by placing a liner on the ground and then placing a perforated pipe directly on the base. The pipe is wrapped in a permeable geoxtextile, which is then covered in 200 mm of clean stone. The stone base forms part of the storage volume of the attenuation system and the Stormbreaker is then assembled directly on top of it. All solids are maintained within the distribution pipe and the water percolates upwards into the Stormbreaker system. Any solids in the pipe are washed through to the outlet manhole, it can also be jetted if required. Again all maintenance is confined to the inlet/outlet manholes and if the perforated distribution pipe is combined with a BMS Petrol/Oil Interceptor up front and a BMS Stormbreaker Defender vortex silt/oil/debris downstream of the isolator row then maintenance is virtually eliminated bar emptying the interceptor and Defender when full. An oil level alarm can even be placed in the interceptor which will alert when emptying is required.
You can watch a video showing a demonstration installation of BMS Stormbreaker at this link including the installation of the perforated pipe; https://youtu.be/4Y-4XbA7kVg
One Stop Shop for Surface Water Management and Design
BMS uniquely offer a ‘one stop shop’ from design to installation for our surface water management products.
BMS can design your full surface water management or SuDS system from first principles. We have invested in specialist software, which produces comprehensive design data. The design will include a full proposal, drawings and design calculations. This service is completely free to our customers.
BMS can also offer advice on sizing/selecting the correct attenuation/infiltration system, petrol/oil interceptor (separator), vortex silt/oil/debris defender, outlet flow controls & storage tanks.
If we can help, please do not hesitate to contact us.
Figure 1: Sample BMS Drainmax Installation
Figure 2: Drainmax Isolator Row during installation
Figure 3: Sample BMS Stormbreaker Installation
Figure 4: Stormbreaker perforated pipe wrapped in a geotextile
Full Customer Question:
How do you calculate the correct size of grease trap for a restaurant, hotel, canteen, pub or cafe?
Answer:
There a number of ways to size and select a grease trap according to EN1825-2:2002 Grease Separators – Part 2: Selection of nominal size, installation, operation and maintenance:
1. Measurement of flow
2. Based on catering equipment
3. Based on type of establishment
4. Special Calculation
All of the methods are complex and time consuming. The good news is that we can do it for you for free! However, in this post we will show you and example of how to do it based on Establishment Type.
The formula is:
This is where is gets complicated!
The Temperature Factor, Density Factor and Detergent and Rinsing Aid are read off tables/graphs:
The Max Wastewater Flow (l/s) Qs requires another calculation!
To this calculation you first need to work out the average flow volume per day from the establishment from the formula and tables below:
So tying it all together and taking the option of a Canteen Kitchen here is a full sample calculation:
- 1200 Meals/day from 07:00-15:00 (8 hours/day)
- t = 8 h
- M = 1200 meals
- Vm = 5 l (from table)
- F = 20 (from table)
- V = 1200/day (M) x 5 l (Vm) = 6000 l/day.
- QS = 6000 l/day (V) x 20 (F) ÷ 3600 x 8 h (t) = 2.33 l/s
- ft = 1.0 fd = 1.0 fr = 1.3
- 2.33 l/s QS x 1.0 (ft) x 1.0 (fd) x 1.3 (fr) = 3.03 l/s
- Nearest separator: NS 4.0 l/s (BMS GT04)
The whole process is quite complicated! Let us do the hard work for you, give us a call on +353 43 3326100 email us or email us on [email protected]
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Full Customer Question
Can you explain how BMS use parallel (lamellae) plates for sewage settlement?
Answer
Thanks for the question. Parallel or Lamellae Plate Settlers have been used to settle solids in potable water treatment for many years. The main criteria to achieve settlement is the upward flow velocity. The is flow in m3 ÷ by the surface area of the settlement tank in m2.
To achieve good settlement you need to achieve an upward flow velocity of 0.9 m/h or better.
For example, for a flow of 10 m3/h you would need at least 11.1 m2 of surface area to achieve an upward flow velocity of 0.9 m/h.
Parallel/lamellae plates radically increase the surface area in a given area. A unique feature of the BMS Blivet is the utilisation of lamella plate settlers in both the Primary Settlement and Final Settlement Zones.
BMS worked with Dr. Michael Rodgers from the National University of Ireland Galway to adapt parallel plates for use in sewage treatment when the Blivet was being developed. The lamellas, at 60° slope and 50 mm (Primary) and 25 mm (Final) spacing, allow the average upward flow velocity of 0.9 m/hr to be achieved in approximately 25% of the volume required for conventional settlement tanks. This is the main contributor to the overall compactness of the system.
A sewage treatment balance tank at a large hotel in Ireland.
You can see how the parallel plates work in the short 3D video below.
A bit about the company
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Full Customer Question
Good morning, I am the manager of a medium sized hotel. We are looking at upgrading our sewage treatment system. We do a lot of events like weddings and conferences and a lot of our customers tend to leave in the morning and come back in the evening as they take advantage of all the amazing local amenities around us. This means that a lot of our flow can come over 4-6 hours per day. Our current system does not handle this very well and backs up/brakes down regularly. Can your system cope with these uneven flows?
Answer
Thank you for your question. We can certainly design a system to handle these uneven flows. A sewage system prefers to have smaller regular flows rather than irregular large once off flows. Therefore, the approach that Butler Manufacturing Services (BMS) would take is two fold. Firstly, we would install a balance tank up front of the sewage treatment system with at least twelve hours capacity. We would fit it with two pumps (primary and back up) that operate on a timer rather than by level controls. In this way the treatment plant with get regular even flows. In the mornings/evenings or during events the tank will fill up and then gradually will pump itself down during quiet periods such as overnight ensuring the treatment plant gets regular flows and does not get overloaded. In the case of the tank filling to capacity, a high level float will switch both pumps on until the excess load is pumped down and the pumps will then go back to the timer.
The second part of the approach is via the BMS Blivet. The BMS Blivet copes with variable loads exceptionally well because it operates by a fixed film of bacteria which grow on the BMS rotors. Growth is directly proportional to the incoming load and cannot be washed away. The BMS Aerotor is also a unique system where the sewage flow has to pass through each Aerotor before moving on the next treatment stage, this is called ‘plug flow’. This means that the Blivet cannot be underloaded, which is great during low season when lower loads will be coming into the plant and growth quickly will ramp up when you experience busy periods. It also means the Blivet cannot be bypassed even in high flows.
We have done quite a few recent hotel installations and are confident that we can provide a low maintenance solution, which will provide excellent sewage treatment and will also last for many years to come. As the Blivet is a completely self contained modular system, it also easy to add on extra capacity in the future when hopefully your operations expand further.
A sewage treatment balance tank at a large hotel in Ireland.
View of a full view of a BMS Sewage Treatment Plant including an up front Balance Tank
A bit about the company
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Thanks for the question.
When calculating the size of a primary settlement tank for domestic type sewage e.g. from a house, school, hotel, camp site or base etc. you are looking to achieve a set upward flow velocity. In the case of a horizontal settlement tank you are generally looking to achieve an upward flow velocity of less than 0.9 m/hr. To do this you need to provide an adequate surface area.
For example, based on population for 400 Population Equivalents (PE) where 1 PE = 200 L of flow and 60 g of BOD:
Flow: 400 PE x 200 l/PE = 80,000 l/day or 3333 l/hr or 3.33 m3/hr.
Standard Upward Flow Velocity = 0.9 m/hr.
3.33 m3/hr ÷ 0.9 m/hr = 3.7 m2 is the minimum surface area required for settlement.
The settlement will often be sized on 3 x Dry Weather Flow (DWF), this would require 3 x the surface area to achieve good settlement.
3 x 3.7 m2 = 11.1 m2 is the minimum surface area required for settlement.
Standard BMS settlement tanks provide a settlement surface area of 1.64 m2 per linear metre. This means that a BMS settlement tank 6.8 m or greater in length will provide adequate settlement.
An innovation that BMS have pioneered in terms of package sewage treatment is using lamellae plate settlers to achieve settlement in a far smaller space. The lamellae plates considerably expand the available surface area for settlement meaning that the required upward flow velocity can be obtained in approx. 1/3 of the space compared to a conventional primary settlement tank design. This one of the main reasons along with the unique design of the BMS Aerotor next generation RBC, that the BMS Blivet is the most compact ‘all in one’ package sewage treatment system available.
Examples of standard BMS Horizontal Flow Settlement Tank & BMS Lamellae Plate Primary Settlement Area built in a BMS Blivet.
A bit about the company
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Thanks for the question. A Package sewage treatment plant is a completely self contained system for sewage treatment that is ‘plug & play’ and should incorporate the following elements in one outer tank;
- Include adequate primary and final settlement/clarification.
- Adequate biological treatment.
- Sludge Storage, preferably at least 3 months.
- Sludge return from final settlement (if required).
- Be delivered ‘ready to go’.
- Fully road transportable assembled.
- Fit inside a standard 40 foot container for transport.
In essence it should be a complete sewage treatment solution that does not require extra tanks to work e.g. extra settlement/sludge storage.
The diagram below shows what a package sewage treatment plant should contain;
Other highly desirable traits;
- Fully portable when completely assembled and can be moved if required.
- Can be placed above/below/partially below ground without a concrete surround.
- Requires minimal maintenance, power and spare parts.
One such system that was designed with the above in mind is the BMS Blivet Package Sewage Treatment Plant, which meets all the above criteria. For this reason it was the only specified package sewage treatment plant for all US Military camps in Iraq after testing against other systems.
The Blivet has been exported via truck/40 foot container to 40+ countries worldwide over 20+ years. It is proven in every conceivable environment and climate extreme.
Figure 2: Blivet Package Sewage Treatment Plant on truck ready for delivery;
Let us know if we can help you with your package sewage treatment plant requirement? BMS offer a free package sewage treatment design service.
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Tommy Butler
Thanks for the questions.
We do indeed have solution for above ground sewage treatment in the form of the BMS Blivet Package Sewage Treatment Plant.
One of the main features of our Blivet package sewage treatment system is that it can be placed above ground free standing with no extra supports. It is also extremely compact, all units can fit in a standard 20/40 foot container. Installation is as easy as lifting it onto hard standing and then connecting the inlet/outlet pipes & electricity. The plant can be fully functioning in a few hours. It also allows the easy addition of extra units if a population increases as it is a complete self contained modular system. This type of installation is especially suited where temporary sewage treatment is required, where the inlet is via a pumped feed, where there is bad ground or a lot of rock close to the surface. To move it to another site is only a matter of emptying it fully and disconnecting the inlet/outlet pipes & electricity. BMS offer a free sewage treatment design service, so please contact us if you require an above ground package sewage treatment system.
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Tommy Butler
We need a discharge license for our car/truck wash. Do you have a solution so that we do not have to get a discharge license or if we are not granted one?
Thank you for your question. We have a great solution in the BMS Recyclone, which can be set up to work in a closed loop with no discharge. Basically, every time you wash a vehicle you lose some of the wash water, approximately 10% is left on the vehicle and 5-10% in evaporation depending on the temperature. The Recyclone recycles 100% of the used wash water that falls down into the collection trap below the vehicle for immediate reuse. However, as you are losing water all the time 15-20% the wash water will have to be topped up to continue washing. Therefore, due to the 100% recycle these is no discharge. At times when the wash is not functioning e.g. at night the wash water overflows from the Recyclone back to the start of the system e.g. holding tank/silt trap/interceptor etc. The system in essence cleans itself at night without discharging. The first tank in the Recyclone is a settlement/sludge tank, which needs to be desludged periodically.
The Recyclone also gives you the bonus of large saving on water charges and as it is completely plug&play is ideal for both new of existing sites and is compatible with all washing systems.
A BMS Recyclone beside a Car/Truck/Van Wash
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Customer Question: How do you calculate expected dry weather flow and Volume of effluent to be discharged per day?
Dry Weather Flow is in essence the sewage flow, from a premises without the addition of any surface water.
Dry Weather Flow (DWF) Full Definition: The average daily sewage flow entering a Sewage Treatment Plant or sewer measured following 7 days without rain (excluding local or Bank holidays etc) and during which on the preceding 7 days, rainfall did not exceed 25 mm on any day.
The volume of effluent is usually calculated using population equivalents (PE) 1 PE is the amount of sewage generated by one person living in a domestic dwelling and is generally taken as 200 L of flow and 60 g of BOD/day. Therefore, the DWF for a 10 PE premises would be:
10 x 200 L = 2000 L.
Full worked examples of how to calculate PE in different situations can be found in our Education Blog in Sewage Parameters 3: Population Equivalent (PE) Parts 1 & Population Equivalents (PE) Part 2. If you have any further questions please do not hesitate to contact Butler Manufacturing Services Ltd (BMS) We will be continuing to be update our education blog with helpful straightforward information on sewage treatment and the terminology surrounding it.
A bit about BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
BMS certainly do, you can find 12 pictures of a rural 50 PE wastewater treatment plant that we recently upgraded below. It includes a BMS BL500 Blivet Package Sewage Treatment Plant, control panel and flow meter. The site contained a lot of spoilage which had to be removed along with other civil works. Also some innovative grading of the ground avoided the need to install lifting pumps as was originally planned, saving money and maintenance in the long and short term. This finish of the site is excellent and blends into the small rural community. BMS can provide a full design and build excellent value fully installed package sewage treatment plant.
A bit about BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Customer Question: When designing a Sewage Treatment process for a caravan park what Population Equivalent (PE) do you assign to each caravan unit?
Dear Customer,
Thank you for your enquiry. The Irish EPA assign the follow figures to Caravan Sites:
Estimating the occupancy of different caravans or mobile homes is more difficult. Generally, it is best to plan for peak occupancy, therefore the normal size of caravan used on site of in general should be ascertained. They have normal occupancy numbers assigned to them and these can just be multiplied by the figures above. If it is an established site their occupancy figures should be analysed and multiplied based on the figures above to obtain the peak occupancy, especially during the July/August peak season.
If it is a new site, the best way might be to try and obtain figures from a nearby (as possible) site. Their figures can then be analysed based on the various plots on the site and an average occupancy per caravan/mobile home/tent per day obtained at different times of the year. This could then be applied to the new site based on their maximum number of plots available.
BMS have over 35 years of experience and are specialists in providing custom sewage treatment solutions for caravan parks, camping sites and hotels.
More answers such as the above can be found in our education blog.
A bit about BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
| Caravan Type | Flow (L/Person/Day) | BOD (G/Person/Day) |
| Touring | 50 | 35 |
| Static (Not Serviced) | 75 | 35 |
| Static (Fully Serviced) | 150 | 55 |
| Tent Sites | 50 | 25 |
Thank you for the question. The BMS Aerotor is actually a next generation RBC, with all the advantages of traditional RBCs such as low maintenance costs and power requirements with none of the disadvantages such as one sided growth placing eccentric loads on the shaft, flow bypass in shock loading conditions and lack of aeration…
Seamus Butler, BMS Managing Director, is the inventor and original patent holder of the Aerotor, which is manufactured at BMS factory in Longford, Ireland and is in more than 50 countries worldwide. The Aerotor is also the biological heart of the world’s most compact sewage treatment plant, the BMS Blivet.
Unlike old activated sludge and RBC systems the Aerotor is a hybrid of active aeration and fixed film reaction with an intense spiral GRP (Fibreglass) media mounted on a rotating horizontal shaft meaning that 97% of the Aerotor’s surface area is actually inside the rotor drum rather than only on the outside as is the case with traditional RBC systems. The rotational media is enclosed in an outer drum to provide active aeration, intense surface area and net hydraulic lift. The BMS Aerotor is self-cleansing and no extraneous pumping or sludge returns are required.
When settled sewage liquor flows into an Aerotor unit, it is piped to the first chamber of the BMS Aerotor which contains a lift rotor. The liquor enters the rotor through 50 mm inlet ports on the peripheral face of the rotor. The rotor is rotating at 6 rpm and the internal spiral formation lifts the liquor and cascades it through the 100 mm sandwich sections, making contact with the surface biomass (fixed film reaction) while actively aerating the liquor. The liquor emerges from the lift rotor below the centre of the rotor on the opposite face to the peripheral 50 mm inlet ports and spills into a captive tray to be conveyed into the next rotor compartment. Here it enters a float rotor below the centre and the same process occurs as in the lift rotor. This continues until the final splitter box in the BMS Aerotor which divides the elevated flow between a 110 mm recirculation pipe and a pipe into the separated final settlement zone. The BMS Aerotor is in essence a plug flow system, which ensures full treatment up to 3 x DWF and up to 6 x DWF for up to 2 hours. The rate of recirculation, which is under gravity due to the 450 mm lift occurring in the lift rotor, can be adjusted by hand stops in the splitter box.
This unique ability to recirculate under gravity means that the flow can be adjusted depending on process requirements and without the need for extra pumping. In low flows recirculation can be set to high to maintain growth and/or maximise treatment. Equally recirculation can be adjusted downwards during high flows. This is especially useful on sites that experience seasonal flows such schools, hotels and caravan parks. The recirculation can also be readjusted upwards to achieve intensive nitrification (the reduction of ammonia) and in the case of the Blivet denitrification (the reduction of Nitrate and Total Nitrogen) in the primary settlement area, which acts as an anoxic zone.
Overall the BMS Aerotor is a world leading package low power & low maintenance solution for package sewage treatment that can achieve multiple high quality effluent parameters such as BOD & Suspended Solids (SS) of less than 10 mg/l, Ammonia of less 5 mg/l, Phosphorus of less than 1 mg/l and Total Nitrogen of less than 10 mg/l.
You can see how the Aerotor works as part of the our class leading Blivet ‘all in one’ Package Sewage Treatment System in the short video below:
Thank you for your question, if you any queries about the above answer or have questions on any areas of package waste water or surface water treatment please do not hesitate to Contact BMS.
A bit about BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
Thank you for your question on the difference between the final effluent standard produced by a package sewage treatment plant and the stream standard.
The difference between the 2 is as follows:
1. Effluent Standard or Final Effluent Standard is the standard of effluent that a given wastewater treatment plant (WWTP) needs to produce based on a set maximum inlet load in terms of Flow, BOD, SS (Suspended Solids) & Ammonia (NH4), Nitrate (NO3), Nitrite (NO2), Total Nitrogen (TN), Orthophosphate (OP) and Total Phosphate (TP) if specified. The outlet effluent parameters are set relative to the influent parameters. N.B. Industrial effluent may have other parameters listed. Package sewage treatment is concerned with the treatment of normal domestic sewage or equivalent.
2. The Stream standard is the standard of the water in a particular water course to which a sewage treatment plant is discharging into. If a stream standard exists the Effluent standard for a particular WWTP is set by working back from the Stream standard. For example if a water course is used for drinking water, bathing or as a fishery, the stream standard and thus the effluent standard discharging into that stream will be set relatively high and will probably include low BOD/SS and NH4/TN/TP concentrations.
However, if a watercourse can provide significant dilution/biodegradation then the stream standard can be set lower, thus resulting in a lower effluent standard.
The stream standard is often set relative to the ‘assimilative capacity’ of a watercourse. This means how much dilution/biodegradation it can provide before pollution such as Oxygen stripping or eutrophication results.
A bit about BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
I have received a laboratory analysis report for effluent from my sewage treatment system and am wondering what the difference between BOD and COD is? Do I need to get both BOD and COD tested?
Thank you for your question. COD stands for ‘Chemical Oxygen Demand’ where BOD stands for Biochemical Oxygen Demand.
It is a test of the amount of oxygen required to oxidise organic matter in a sewage sample by chemical oxidation with a powerful oxidising agent such Potassium Dichromate. COD is closely related to BOD or Biochemical Oxygen Demand, the difference being that BOD is a test of the level of organic matter that can be biologically oxidised while COD is a test of the amount of organic matter that can be chemically oxidised. (A full explanation of any of the parameters can be found by clicking on the blue links).
The higher the BOD/COD the more oxygen stripping capacity the discharged effluent has when discharged into receiving waters (oxygen is used biologically/chemically to break down the organic matter) and the more potential for damage to biological life in those waters.
COD is normally higher than BOD because more organic compounds can be chemically oxidised than biologically oxidised. This includes chemicals toxic to biological life, which can make COD tests very useful when testing industrial sewage as they will not be captured by BOD testing.
In regards to normal domestic effluent e.g. BOD & Suspended Solids (SS) 300 mg/l, which is usual for package sewage treatment systems, COD is not always stated as part of the discharge license. If it is not part of your license you do not need to get it tested. However, COD does have a big advantage over BOD in that the test only takes approximately three hours, as opposed to the five days required for BOD testing and it is usually possible over a period of time to establish a ratio of BOD:COD, which allows extrapolation of the BOD.
More information can be found by clicking on the Chemical Oxygen Demand Link.
A bit about BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements.
We still have a few more questions to answer as regards Petrol/Oil Interceptors (Separators), next up; What is the difference between a Class 1 and Class 2 Separator?
Petrol/Oil Separator:
Another word used to describe an interceptor.
Class 1 Interceptor:
Designed to achieve a concentration of 5 mg/l of petrol/oil at discharge under normal conditions, includes a coalescer. A Class 1 Interceptor is usually required for discharge to any surface water.
Class 2 Interceptor:
Designed to achieve a concentration of 100 mg/l of petrol/oil at discharge under normal conditions. Normally used when discharge is to a foul sewer.
BMS have introduced a full set of Petrol Interceptor/Holding Tank Sizing & Selection Charts to help you easily size and select an Interceptor/Holding Tank suitable for your requirements. They can be downloaded at this link.
A Load of BMS Petrol/Oil Interceptors
A bit about BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
We would be delighted to discuss any requirements.
Following on from last week’s question on the difference between a Petrol/Oil Interceptor & a Separator, another customer asked; What are the different types of Petrol/Oil Interceptor (Separator) and what is the difference between them?
There are 2 main types of Petrol/Oil Interceptor;
Full Retention Interceptors, which are designed to treat the full flow delivered by a drainage system up to 50 mm/hr.
Bypass Interceptors which, are designed to treat flows of up to 5 mm/hr. This covers 99% of rainfall.
A Full Retention Interceptor is normally used when there is a risk of regular contamination of surface water run off with petrol/oil and/or the risk of larger spills e.g. vehicle maintenance areas, heavy goods parking areas or where frequent vehicle manoeuvring takes place.
A Bypass Interceptor is normally used when there is a risk of infrequent light contamination of surface water run off with petrol/oil and/or the risk of only small spills e.g. car parks, airports, industrial estates, roads and other low risk areas.
Under normal flow conditions the BMS Full Retention Interceptor is designed to retain the full contents of an oil spill or contamination up to flows of 50 mm/hr. For flows under 5 mm/hr a bypass interceptor functions in the same way. In the case of storm water flows above 5 mm/hr an internal vortex a rrangement allows the stormflows to bypass the retention chamber, this has the benefit of considerably reducing the size of the interceptor required while still treating 99% of rainfall. The majority of pollutants in any storm water event will be trapped before the bypass takes place.
BMS have introduced a full set of Petrol Interceptor/Holding Tank Sizing & Selection Charts to help you easily size and select an Interceptor/Holding Tank suitable for your requirements. They can be downloaded at this link.
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations. We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. Let us know when suits.
A Load of Bypass Interceptors leaving the BMS Factory
We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience. Please do not hesitate to contact us.
The last in our customer questions regarding Petrol/Oil Interceptors/Separators is; How do you calculate the size of a Petrol/Oil Separator needed for a site?
Firstly you need to determine if you require a Bypass Interceptor or a Full Retention Interceptor; this is answered in a previous Customer Question answer; What are the different types of Petrol/Oil Interceptor (Separator) and what is the difference between them? Secondly you need to determine if you require a Class 1 or Class 2 Interceptor; this is also answered in our last customer question answer; What is the difference between a Class 1 & Class 2 Separator?
After selecting the interceptor size and type, the correct size of interceptor is based on the flow into it based on rainfall onto a given surface area, this is known as nominal size or NS.
Each interceptor is allocated a nominal size based on EN858; the European Standard for Interceptor Design and Sizing. This will indicate the nominal flow that the interceptor is sized for e.g. 4 l/s. A full retention interceptor with a capacity of 4 l/s would be designated NS04 while a By-Pass interceptor with the same capacity would be designated NSB04.
(Please note Petrol/Oil Separator and interceptor mean the same thing)
Example 1
An interceptor required for a 25,000 m2 car park discharging into a local authority surface water sewer.
As there is a low chance of oil spillage a Bypass Interceptor would be most appropriate.
As discharge is to a surface water sewer a Class 1 Interceptor, which is designed to achieve a concentration of 5 mg/l of petrol/oil at discharge under normal conditions and includes a coalescer and a closure mechanism is most appropriate. A Class 1 Interceptor is usually required for discharge to any surface water.
Based on EN858 a drainage are of 25,000 m2 gives a nominal size (NS) of 45 l/s.
So in this case BMS would select a BMS PB5 Class NSB 47 l/s Bypass Interceptor, which is the closest available in our range.
Example 2
An interceptor required for a 1,700 m2 fuelling area discharging direct to surface water.
Due to the high risk or fuel spillage a Full Retention Interceptor designed to contain the full contents of a full spill is required.
As discharge is to a surface water a Class 1 Interceptor, which is designed to achieve a concentration of 5 mg/l of petrol/oil at discharge under normal conditions and includes a coalescer and a closure mechanism is most appropriate. A Class 1 Interceptor is usually required for discharge to any surface water.
Based on EN858 a drainage area of 2,600 m2 gives a nominal size (NS) of 47 l/s.
So in this case BMS would select a BMS PB9 Class 2 NS 47 l/s Full Retention Interceptor, which is the closest available in our range. Please note that the Nominal Size of a Full Retention Interceptor can also be denoted as NSF e.g. NSF; 47 l/s.
BMS have introduced a full set of Petrol Interceptor/Holding Tank Sizing & Selection Charts to help you easily size and select an Interceptor/Holding Tank suitable for your requirements. They can be downloaded at this link.
A bit about BMS
BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world. It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more. Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link
A BMS PF10 Full Retention Interceptor arriving on site in Malta
