Tradition Type II Marine Sanitation Devices – is common in most cargo ships wherein sewage is treated using biological treatments and chlorination. However, many cruise ships do not make use of biological treatments for sewage but chlorination and maceration. The system also includes the removal of biochemical oxygen demand and some nutrients through aerobic biological treatment, clarification and filtration for the removal of solids, chlorine disinfection for the destruction of pathogens and screening for the removal of grit and debris.
Advanced Wastewater Treatment Systems – are designed to result into effluent discharges of high quality and purity that surpasses the standards for secondary and tertiary effluents and reclaimed water. However, advanced marine sewage treatment systems are still at the development stage but they generally provide improved screening, biological treatments, solid separation through flotation and filtration and disinfection using ultraviolet light. Some of the systems are tailored for any ship size and carries out sterilization of the treated effluent through chlorination, UV treatment or both to provide flexibility during operation under different maritime operations.
Comparisons of marine sewage treatment systems
Most of the traditional types of sewage treatment operate on vessels with errors because they have only been installed on the later part of the system before its arrival to port. There is usually a reduction in bio-sludge, over chlorination or disruption by the intermittent flow that is common to ship life. Advanced marine sewage treatment systems are offered by different companies and they are generally more complex but produce better results in effluent quality. These advanced systems are typically found in cruise ships with large amounts of wastewater and sewage. Most of the are currently improving their technologies and developing new systems to reduce pollutants like heavy metals, nutrients, phosphorus and nitrogen from polluting the marine environment.
The impact of sewage on marine environment
The adverse effects of sewage on marine environment are well documented in coastal areas. One of the sources of sewage pollution is uncontrolled discharges from recreational craft that converge in numbers closer to inshore. In spite of the fact that most of these recreational crafts are fitted with holding tanks, their effectiveness is often dependent on the availability of inshore disposal facilities. The availability of inshore disposal facilities is not too common but many harbors are now realizing the importance of providing these facilities to reduce oxygen depletion and diseases-causing bacteria on the waters.