Review of marine outfall systems in Taiwan

Abstract

There are three marine outfall systems in Taiwan called Da-Lin-Pu (DLP), Chung-Chou (CC), and Tso-Ying (TY), respectively. All of the systems are located in the south of Taiwan along the 20 km long coastline of Kaohsiung City. The DLP and TY systems are discharging industrial wastewaters, while the sewage produced from Kaohsiung City with population of 1.4 million is discharged into the ocean through the CC marine outfall system. The lengths of the DLP, CC and TY outfall pipes are 3350, 3000 and 5045 m, respectively, and all three are designed with the same initial dilution ratio of 100:1. The three systems are located within a 20 km long coastline. Thus the ocean climate and seawater quality of the outfall field are similar to one another. On average, the coastal current flows mostly southeastwards with velocities ranged between 30 and 40 cm/sec, while the average tidal range is about 47 cm. Generally, the seawater quality in the outfall fields is still under the limiting criteria. However, the concentrations of phenols and oil and grease are found, sometimes, higher than the limiting criteria. This is probably because the wastewaters are mostly from petrochemical plants, and the outfall fields are near the Kaohsiung Harbor. Since the concentrations of N and P nutrients in the seawater are still below the limiting criteria, the problem of “red tide” has not yet occurred in this oceanic area.