Ship ahoy with VisiFerm DO Arc
Hamilton’s optical dissolved oxygen sensor suited for sewage treatment plants on ships
The sensor VisiFerm DO Arc of Hamilton Bonaduz AG is perfectly suited for sewage treatment applications on cruise and river cruise ships. In this way, it supports compliance with the Directive 2012/49/EU of the European Commission. This directive stipulates that as of 2016 discharging water into the environment without prior treatment is forbidden and hence sewage treatment plants are mandatory on ships. Plenty of water is contaminated on board due to laundry, toilet and sanitary facilities as well as galleys. When discharged into surface water, the oxygen-consuming wastewater has a negative impact on the environment. Consequently, contaminations or, in the case of ballast water, carry-over of animals into waters, in which they are non-native are caused. In order to limit contaminations biological and chemical oxygen demands of water are limited. These parameters describe how polluted water is. The water on board is treated biologically with the help of aerobic bacteria. These are immobilized on carriers maximizing the active surface. The carriers swirl through the water in a moving bed bioreactor. In this way, oxygen is added and dissolved in the wastewater. This ensures an optimal metabolism, reduces the chemical oxygen demand and allows an efficient wastewater treatment. Furthermore growing on carriers helps to protect the bacteria, leading to a robust wastewater treatment and a reduced sludge production. The dissolved oxygen content is measured using VisiFerm DO Arc with a shaft length of 425 mm because it’s insensitive to changing water levels in the tank as the sensing part is always in touch with the media. Another advantage of the optical sensor is that the measured values are processed in the sensor head and communicated directly via a 4-20 mA interface to the process control system. This allows an installation at any point in time without requiring further equipment such as external transmitters.