Wastewater treatment in the marine industry

Transcription

1 Wastewater treatment in the marine industry AUTHOR: Wei Chen, Head of R&D, Wärtsilä Water Systems Ltd Over the past years or so, wastewater treatment on land has been successfully developed. However, the marine industry is still working to develop its means of treating wastewater, and Wärtsilä is actively developing the needed technologies for ships. Just about years ago, the wastewater treatment process was invented when our aqua environment began to deteriorate. The science, engineering, and regulations relating to water and wastewater have evolved slowly but steadily ever since. As a result, the efforts of municipalities and land-based industries have led to significant improvements in water quality, and the way that it is treated. The marine industry, meanwhile, continues to explore means of developing its methods in this area. So-called grey water is the effluent from living areas, laundries, and galley areas, while black water is the output from toilets. On land, these waters are collected from our households and professionally treated in wastewater treatment works (WWTW). On a ship, black and grey waters are collected separately, but often become mingled during transport, storage and discharge. Annex IV of IMO's MARPOL Convention, adopted 40 years ago, set ambitious standards for ship discharges in 2(VI). But there are two shortfalls: 1) grey water is not regulated, and 2) discharges from ships have not been monitored. Grey water pollutes. On land, nobody expects the grey water from a restaurant or laundry to be dumped into a natural water body without treatment. There are numerous wastewater engineering text books that explain the scientific basis in detail 61

2 [ MARINE / IN DETAIL ] [ MARINE / IN DETAIL ] Faecal Coliform (MPN/ ml) Table 1 Characteristics of grey waters on ships (USEPA report, 2008) BOD5 (mg/l) 2 (VI) black water discharge limits Acoommodation Grey Water 37,000, Galley Grey Water 29,000,000 1,490 Domestic Wastewater 1,000,000 to,000, to ,000,000 1,000,000,000 10, Coliform Geometric Mean (count/ ml) Average BODS (mg/l 02) Fig. 1 Average performance of wastewater treatment plants on ships (Blue bars cruise ships with AWTS in Alaska; red bar 32-ship survey in a European port). for such treatment. Grey water on ships is just as polluted (Table 1), and Faecal Coliform concentrations in grey water exceed the discharge limits of black water by,000 times. Grey water also accounts for 80% of a ship s wastewater organic (or Biochemical Oxygen Demand BOD5) loading. Annex IV only covered 20% of a ship s wastewater pollution impact. The technologies are available. After The U.S. state of Alaska established that cruise ship discharges were of poor quality, federal legislation expanding Alaska s authority over cruise ship discharges was swiftly passed in Strict rules regarding both grey and black water were then introduced. This led to the development of a new generation of Advanced Wastewater Treatment (AWT) systems, which have subsequently exceeded all expectations (Figure 1). This success has led the USEPA to extend the stringent grey water requirements to other US waters (Vessel General Permit, 2008). Most importantly, Alaska has established the Commercial Passenger Vessel Environmental Compliance Program (CPVECP), the one and only independent monitoring and sampling regime in the entire global marine industry. AWTs that were fit for purpose survived, and those not were weeded out. Despite being endorsed by the USEPA as being the Best Available Technology, and while out-performing WWTWs ashore, AWT has no clear definition, nor can it be Type Approved as such. It must do what it says on the label, year on year, under the watchful eyes of CPVECP. It was not easy, but Alaska has provided a show case of stakeholder commitment to protect its pristine marine waters. Wärtsilä has worked with cruise operators to develop its Membrane Bio Reactors(MBR) system. MBR works by segregating or splitting the treatment of black and grey water on the basis that the latter is less contaminated and should be treated separately. The solution has proven to be extremely successful in meeting all the Alaska criteria. The marine industry needs universal regulations. In addition to Alaska s clean-up efforts, the Great Lakes, US waters (EPA Vessel General Permit, 2013), and inland waterways in Europe (2012/49/EU) have also regulated 62 in detail

3 grey water treatment in various shapes and forms (Table 2), each affecting certain shipping sectors. There are already four sets of different type approval specifications, and more than five different compliant regimes. This assortment of legislation is a source of confusion for both vendors and ship operators. The challenge is further emphasised by the fact that some ports and coastal waters ban all discharges, regardless of the existence or type of AWTS onboard. Ships often have to hold wastewater in double bottom tanks, for discharge outside the restricted waters, at the expense of extra fuel costs and emissions. Classification Societies also promote grey water treatment by offering greener Class Notations. Almost all type approved sewage treatment plants claim the capability to treat grey water, while more and more ship owners and yards are signing up to these initiatives. For example, the cruise industry some years ago voluntarily stopped discharges of untreated grey water into the Baltic Sea. The industry saw what s coming, and is ready to meet new legislation. However, the variations in requirements in different parts of the world can create confusion regarding equipment selection, system design, and operations. For instance, grey water is sometimes treated only during the very last stage of a type approved sewage treatment system, which results in noncompliant performance. At the international level, the lack of grey water regulations has started to affect other IMO policies as well. One example of this is that the positive efforts to accommodate ballast water tanks for holding grey water under certain operational conditions, has been stalled. Attempts to address grey water pollution along the Northern Sea Route under the Polar Code have also faltered. While the needs to control grey water in the marine industry are just as great as they are on land, Annex IV unfortunately provides no provisions for monitoring discharges from ships. The discharge limits are only applicable to a type approval test at a testing facility. Compared to the detailed specifications of the CPVECP, i.e. the overboard discharge sampling point, logbooks, flow measurements, sampling frequencies and procedures, etc., Annex IV lacks such monitoring requirements totally. This weakness has been exploited. Type approved sewage treatment plants that utilise the rich oxygen in the sea water to Fig. 2 MBR installations on a new built cruise ship. Fig. 3 MBR construction on a new built cruise ship in the ship yard. in detail 63

4 [ MARINE / IN DETAIL ] [ MARINE / IN DETAIL ] remove pollutants by drawing sea water through them, at as much as more than 40 times the sewage flow, are installed on hundreds of ships. Dilution is, alas, a poor means of controlling pollution, and in 2016 constraints will be imposed via 227(64), albeit with a lack of enforcement measures. Even then, the practice will continue to entertain the notion of marine water protection without enforcement. In 2012, one member state surveyed the performance of sewage treatment plants onboard 32 ships. It was found that the vast majority of the equipment did not meet the existing sewage treatment standards due to improper use of detergent, a lack of maintenance, or not following the operational instructions (MEPC 64/23). Actually, none of the ships satisfied even the most relaxed 2(VI) rules adopted in 1973, and the average results missed the targets by a long way (Figure 1). This despite the fact that during the past five years 2(VI) has been tightened twice (159(55) and 227(64)). The fact that grey water is often intermingled with black water in the tanks and pumps makes it difficult to create effective monitoring. Alaska's CPVECP, on the other hand, deals with this problem very well. Fig. 4 MBR retrofitted in-situ while the ship was trading. The industry welcomes science based regulations It is not always the case that laws become more effective when made increasingly stringent. An Alaskan State Law passed in 2006, for example, demanded that cruise ships meet the state s water quality standards at the point of discharge. This made drinking water appear to be toxic to the ocean. It took an independent Science Advisory Panel to conclude that this law should be rolled back since such a requirement is not relevant, and is anyway not applied to shore-based discharges. The process lasted three years, but at least it reached a science-based closure. Wärtsilä has achieved world leading status as a technology provider of future-proofing black and grey water management systems for ships. The situation is not, therefore, that effective treatment is not yet available. It is the will to ensure that this treatment is carried out that appears to be lacking, and the fact that 32 ships exceeded the IMO's discharge limits by a factor of 0 gives cause for concern. Regarding the removal of nutrients from ship sewage discharges, the Baltic Sea has been designated by the International Maritime Organisation (IMO) as being a Particularly Sensitive Sea Area under its MARPOL Annex IV. However, passenger ships have contributed just 0.035% of the Baltic Sea s nitrogen load,and even this minute contribution hasbeen diverted to port reception facilities, thanks to the cruise industry s proactive stance since Nevertheless, this effort has failed to win the hearts and minds of the Baltic rim countries. In 2012, a proposal was adopted to make the discharge levels of nutrients from passenger ships more stringent than equivalent standards ashore. This was branded by industry groups as being a sad day but there were, nevertheless, a number of member states wanting to implement these standards also for the Mediterranean, and other sea areas. By the way, the Mediterranean Sea is defined as nutrient-poor water by the European Environmental Agency. Had there been an independent Science Advisory Panel or a monitoring regime, this confusion could have been avoided. Fortunately, more regulators, at least those ashore, have recognised that environmental initiatives can have an adverse impact by consuming natural resources, and incurring emissions that need to be justified by the tangible benefits they may bring. Having science based rules is no longer a question of the more stringent the better. Since it takes more than aspirations to find a balance, the rules can and should be science based, practicable, and sustainable. When it comes to black and grey water pollution from ships, maybe it is time for the marine community to do something simple, and to do it right, such as regulating both black and grey water - and having such regulations enforced. 64 in detail

5 Wärtsilä Water Systems Ltd is an innovative, market leading company providing conventional and advanced wastewater treatment systems in response to environmental needs and marine legislations. During the past 40 years, the company has provided over 8000 installations across all ship sectors. Building on the success of its advanced Membrane BioReactor technology, the company has developed a unique wastewater management system that allows future proofing compliant operation at low operational costs and with minimum skill requirements. This system has been successfully implemented on multiple cruise ships, many of them sailing in Alaska waters. Table 2 Key regulations on black and grey water discharges from the ships. Standards IMO MARPL Annex IV EU USA Alaska 2 (VI) 159 (55) 227 (64) 2012 (Inland Water ways) USC G 33CFR 159 Type II MSD EPA Vessel General Permit USC G 33CFR159 Subpart E GP No DB0026 Continuous (Underway) Water Quality Standards (AWQS) Enter into force Applicable streams Black Black Black Black & Grey Black (Grey in Great Lakes) Grey Black & Grey Type Approval IMO IMO IMO EU USCG N/A N/A Applicable ships AII AII AII AII AII 499 >500 Passenger > 500 Passenger > 250 F. Coliform (/ ml) TSS (mg/l) 35 35Qi/Qe BOD (mg/l) Qi/Qe COD (mg/l) Qi/Qe 125 TOC (mg/l) 45 ph 6~8.5 6~ ~9 6.5~9 6.5~ ~8.5 Chlorine (mg/l) TN (mgn/l), Special Area, passenger > 12 TP (mgp/l), Special Area, passenger > Qi/Qe or 70% 1 Qi/Qe or 80% Ammonia (mgn/l) 28 (130) 1 Dis. Copper ( g/l) 87 (130) 3.1 Dis. Nickel ( g/l) 43 (43) 8.2 Dis. Zinc ( g/l) 360 (360) 81 in detail 65