Nutrient Analysis of Food Waste from Ships’ Greywater in the Baltic Sea

This case study presents the results of assessments of the potential risk of pollution by food waste in different applied shipping scenarios. A four-step model was used to analyse the applied procedures. The first step of the study involved the identification of possible strategies for on-board food waste management. In the second step, physicochemical tests of visually selected greywater detected high contents of nutrients (NTotal ≤ 238 mg·L−1 and PTotal ≤ 71 mg·L−1). Daily nutrient content (DNC) calculations of different food waste management scenarios allowed us to estimate the highest emission value from the discharge of greywater mixed with shredded food waste in the third step. In the final stage of the study, the results obtained made it possible to qualitatively assess the impact of DNC load on food waste management methods in the Baltic Sea environment. This study highlights the potential risk of polluting the Baltic Sea with nutrients and other contaminants in various scenarios, which will impact the marine recovery process. The presented research helps to outline waste management approaches for the reduction of these risks

Microplastics in Ship Sewage and Solutions to Limit Their Spread: A Case Study

The case study presented in the paper is the first in the field to find microplastic (MP) particles in both grey water (GW) and post-treatment sewage (TS) samples, which can also be legally discharged into specially protected areas. Compiling a data set of 50 water samples collected from the GW and TS samples of 5 transport ships involved in the case study, we show that the mean number of separated microparticles in the GW samples n = 72 particles per litre, and in the TS samples n = 51 particles per litre. Of the 614 separated particles, the most common were fibres n = 285 (46.4%), followed by other (various) hard particles n = 226 (36.8%) and soft particles n = 104 (16.8%). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) identification was mainly in the form polyethylene (PE), polypropylene (PP) (solid particles and films), polyesters, polyamides, and acrylic fibres. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis revealed ecotoxic chemical elements on the surface of these particles. Our results show that the sewage treatment facilities installed on ships need to be improved, and we developed a solution for this. The findings of the case study certainly deserve further attention and serve as an impetus for research on the improvement of ship wastewater treatment facilities