While the ratification for the IMO's BWM Convention has recently been approved and will come into force in September 2017, the USCG's Type Approval & AMS regulations will take more time. However, the prospect of both is pressuring key industry players to seriously scrutinize the validity of available BWT systems for present and future deployment.
These systems operate in challenging conditions across the globe and so the filtration component of these systems has become an integral component of the overall system because of its ability to validate system efficiency and, in some circumstances, even successful operation to regulation standards.
Figure 1. The Filtersafe patented Everclear System.
Ballast water treatment (and filtration) is an application exposed to an array of different water conditions and is also susceptible to challenging operating conditions as maritime vessels travel the world. Water quality and density at uptake can vary dramatically depending on the season and the location with water exhibiting profiles typically found in freshwater, brackish water and seawater.
Salinity levels in ballast water treatment (BWT) systems are often in the range of 3.1%–3.5%, though they can be even higher in some regions. These variances, along with changing water temperatures, result in a broad gamut of organic matter requiring filtration prior to treatment. Species are typically segregated into two bands; Phytoplankton (10–50 micron) and Zooplankton (>50 micron).
Moreover, a BWT system is exposed to dramatic levels of sediment (TSS) in many ports, which further affects a system's ability to eradicate organic organisms at the disinfection stage. It is due to both these factors, the high loads of organic matter and TSS, that filtration is required to play such a significant role in a system's performance and commercial viability.
Removal of TSS prior to disinfection is a markedly more effective process because the latter stage then has less turbidity to contend with when nullifying the threat of organic matter. This usually has a direct correlation to a system's energy consumption, time in operation and chemical loading. In addition, and just as importantly to the end user, it ensures a lower operating cost. Removal of organisms at a pre-treatment stage as opposed to at the disinfection stage also has a direct effect on the efficacy of a system as it reduces Biological Oxygen Demand (BOD) & Chemical Oxygen Demand (COD) at the time of disinfection.
In light of these challenges, BWT system providers are almost unanimously selecting screen filtration as their pre-treatment solution to protect costly disinfection units from such challenging and dramatically varying waters at uptake. Screen filtration has been proven to provide distinct advantages over other methods of filtration in this application. BWT vendors have recognised that leading screen filtration technology is capable of removing a large quantity of foreign material from a variety of water types whilst maintaining a very high flow rate to service the requirement of an expedient ballasting process.
Ballast Water Treatment systems are also susceptible to a number of technical constraints which are especially concerning in retro-fit projects. Often, the key design constraints of these systems revolve around filter footprints as well as access for installation and maintenance (both critical factors in being able to install a system in non-compliant vessel). However, other key concerns include the specification and location of existing system infrastructure namely the ballast water pump size and its location. This often leads to pressure concerns at the inlet of a system as it is not uncommon to have a ballast water pump some distance from the location of the retro-fit system (especially noticeable in large vessels like a VLCC vessel which require flow rates of up to 7400 m3/hr).
Responding to the BWT challenge
Filtersafe is a key supplier of automatic screen filters to the industry and has been since the market's inception. Throughout the last decade, as the BWT market has moved out of its infancy, it has become clear to many that the industry is hinged on filtration solutions at the pre-treatment stage.
As of 2016, almost all key BWT systems providers acknowledge and rely on automatic screen filtration in order to meet the required regulatory performance standards. By listening to the market over the course of the last decade and working with its customers, Filtersafe has developed automatic screen technology that provides a reliable and easily adopted filtration solution.
Drawing on its experience in screen filtration, the company has re-engineered the automatic screen filter concept to respond to the specific challenges in the application of ballast water filtration. This directly translates to automatic screen filters specifically designed to adhere to classification standards utilized by the maritime industry. In addition, Filtersafe has added to its offerings by developing patented technologies specifically to address the rigours presented in water with high loads of TSS and organic matter.
Reliable filtration is essential for BWT
Filtersafe's ability to service the ballast water market lies in its filtration solutions. By utilising its exclusive cleaning technologies, the company is able to confidently specify 25, 40 and 50 micron automatic screen solutions that BWT systems providers and shipowners can rely on. In fact, Filtersafe has conducted extensive testing worldwide in the most challenging of conditions to ensure its automatic screen filters are always clean and reliably return to the nominated differential pressure.
It is clear that the pre-treatment filtration market of Ballast Water Treatment differs greatly from other applications. Where typical screen filtration applications normally operate above the 50 micron range, BWT requires consistent and reliable filtration as low as 25 micron in some instances.
Filtersafe is able to respond specifically to these challenges with its Smartweave and NozzleX technologies, which are having a profound impact on the industry's interpretation of automatic screen filtration for BWT pre-treatment. Filtersafe intends to generate further product development in this market segment as well as others with its patented automatic screen technologies.
Figure 2. Typical Filtersafe MULTI filters installation on-board a vessel.
Figure 3. Filtersafe Retrofit installation.
Figure 4. BS-603, a typical Filtersafe filtration unit capable of handling up to 1800 m3/hr.