An integrated full-scale system for the treatment of real ship domestic wastewater: Shore-test experiments

With the increasing number of ocean-sailing ships, the pollution of the oceans' water caused by the discharge of ship wastewater has become one of the serious concerns for the whole world. Most of existing ship wastewater treatment studies were carried out in bench/pilot-scale and cannot meet the latest discharge standards of In-ternational Maritime Organization (IMO) and China. To overcome those barriers and prepare for the onboard test, we evaluated the hydraulic retention time (HRT) variations (10.5-12 h) for treating low COD/TN ship wastewater by a full-scale oxic-anoxic micro-sludge membrane biofilm reactor (O-AMSMBR) system. The full-scale O-AMSMBR achieved over 82 % removal of chemical oxygen demand (COD) and 76 % removal of total nitrogen (TN) from a ship wastewater with continuous operation at a HRT of 10.5 h. Although anoxic membrane biofilm partly compensated for the deterioration of TN removal in performance of the aerobic sludge, the effluent TN concentrations still cannot meet IMO discharge standards at HRT as low as 9 h due to the inhibition of simultaneous nitrification and denitrification (SND) by low HRT and C/N. Wavelet Neural Networks (WNN) was used to explore the removal mechanism under HRT variations. Simulation results show that HRT andinfluent pollutant's concentration are the two most sensitive factors for COD and TN removal in daily operation so special attention should be paid to the dramatic change of influent flow rate in ship sewage treatment operation. In particular, techno-economic analysis was conducted in this study to provides a baseline for developing economic options for ship wastewater treatment in practice.