An overview of MMF & high volume water filtration for a maltster in Perth, a water-hungry industrial process.
Ancient brewing & malting techniques. Source: Wellcome Collection.
Malting is one of those interesting occupations that’s been around since the dawn of time. Although the true origin is lost to history, ancient Egyptians supposedly placed malt into a wicker basket which was then lowered down into open wells. After steeping in the cool, pure well water, the malt undergoes germination and drying before becoming a finished product. From there, malted grain can be used to make beer, whiskey, and a range of products in the food & beverage industries.
Modern malting processes appear quite different, but the principles are the same. Importantly, water is still a critical component in the water-hungry process of industrial malting. On average, for every tonne of malt produced, around 5m3 of high purity water is required for the steeping process. Water filtration systems designed to produce such high volumes of water must be highly efficient, robust and easily maintained.
Advanced Watertek was contracted to design, manufacture, and commission a high volume industrial water filtration solution for an established malting company in Perth. The system had to be containerised and self-sufficient, and was required to produce 1,200m3 of highly filtered product water per day. This filtered water was to be utilised for steeping, still a water-intensive process.
Containerised filtration systems are mobile, weatherproof, and self-sufficient.
The malting facility was located only 20 kilometres out of Perth, capital of Western Australia. Our client was drawing their process water from the municipal supply, meaning the water was already potable and relatively clean.
Unlike many of our jobs, we didn’t need to remove any soluble salts from the feed water via reverse osmosis. Chlorine removal was being done downstream, so we only had to bring total suspended solids (TSS) down to an acceptable and controlled level. Most industrial processes benefit from a low level of TSS in feed water. High levels of suspended solids can affect coagulation, mixing and disinfection efforts.
Multimedia filled pressure vessels do the work in multimedia filtration (MMF).
The volumes of water called for two multimedia pressure vessels - polyethylene tanks wrapped in fibreglass for strength. These multimedia vessels and their contents form the heart of the filtration system. Stainless steel fixings and supports create a skeleton, and Schedule 80 PVC valves and fittings carry the water throughout the system. Roughly 25,000 litres of filtered water flows out of each pressure vessel every single hour.
Principles of multimedia filtration (MMF)
Multimedia filtration (MMF) is a process via which suspended matters and sediment is removed from water by passing it through a suitable filter media. In this case, we used three different medias forming six individual layers.
- 3 layers of gravel
- 2 layers of sand of different size
- 1 layer of anthracite
The raw water containing suspended matter and turbidity passes through the filter bed, which traps matter of gradually decreasing size. The efficacy or selectivity of multimedia filtration can be designed to requirements, depending upon the type of media used in the filter. With the combination of media above, our system performs reliable sediment filtration down to less than 20 microns.
Manual backwash valves for each multimedia pressure vessel.
Principles and importance of backwashing.
Multimedia sediment filtration is a physical removal of suspended matters from water. Over time the filter bed traps and accumulates these suspended solids. This sediment build-up will increase resistance to the flow of water through the bed, potentially decreasing production rates. To prevent this happening and interfering with production, the filter bed needs to be backwashed at regular intervals.
To perform backwashing of a multimedia pressure vessel, a large amount of water is passed at a low pressure through the filter bed in the opposite direction to the service flow. This backwash flow loosens the bed and removes accumulated matter, carrying it toward the drain. Normal backwashing frequency depends upon the sediment load in the raw water and the size of the filter bed, however, a typical frequency is once every 24 hours for an average duration of 15 minutes.
A good filtration system makes backwashing a simple task for operators, knowing that our systems will always outlast the average employee lifetime. In the case of this particular job, there’s five butterfly valves, each clearly demarcated between normal operation and backwashing procedures. For this job, they’re manual. Manual valves are cost effective and durable. You can however opt for full automation, which is common with larger jobs. Motorised valves, combined with a control panel and PLC, will do this job for you automatically, every day without fail.
Containerised filtration systems are plug and play – just connect and go.
The filtration system was manufactured and delivered in roughly 8 weeks. The containerised systems are completely plug-and-play – all they need is a connection to an inlet and to a drain. The municipal water supply provides adequate pressure, so no pumps are required to force water through the system.
Simplicity. That’s what this job, and this article, are all about. The end result is a highly reliable, independent source of highly purified water ideal for industrial applications such as malting, brewing, or any food and beverage application.
If you’re considering a high volume filtration solution, there may be viable alternatives to MMF, depending on your requirements. Advanced Watertek have also previously installed stainless steel screen filters on a municipal water supply to provide high volume water filtration for a hotel in the Perth CBD. MMF was out of the question due to space restrictions. These types of screen filters are state-of-the-art, self-cleaning and highly efficient.
Multimedia filtration is ideal for many high volume filtration jobs because it’s resilient. Gravel, sand and anthracite takes a long time to wear out, and this is extended further with correct backwashing protocols. Plus, it’s low maintenance and low cost. We recommend replacing the multimedia every three years on average. Sand and gravel aren’t expensive, so you won’t be caught out by expensive maintenance years down the track.
Three years later our malting client got back in contact. They were scaling up and wanted another system, exactly the same.
Advanced Watertek manufactured, delivered and commissioned an identical MMF system right alongside the first unit. This doubled production capacity to 2,400m3/day, or 2,400,000L/day.
Containerised water filtration systems installed at malting facility, Perth.
Bad systems don’t last. Good ones do.
The two systems have now been in place and in operation for 11 and 8 years, respectively.
The process of water filtration is complex – but it’s not complicated. A well designed filtration system will employ simple principles. This should lend itself to a durable, low-cost and easily maintained solution. Whichever method of filtration you choose, a good water treatment system should work for you, not the other way around.