Technology Selection for Wastewater Treatment in the Maldives

Abstract

In the Maldives, the discharge of untreated wastewater into the sea poses a significant threat to public health and the marine environment. This study proposes technically feasible, sustainable, and economical wastewater treatment technologies appropriate for small islands in the Maldives. Out of the 187 residential islands in the Maldives, three islands (HA. Dhidhdhoo, HA. Hoarafushi, and HA. Ihavandhoo) were selected as study areas. This study characterized the wastewater from these islands using physiochemical and microbiological water quality assessment parameters. The Water and Wastewater Treatment Technologies Appropriate for Reuse (WAWTTAR), an open-source software developed by the Humbolt State University in 1993, was used to simulate the performance of different wastewater treatment processes to treat the characterized wastewater. The feasible alternatives identified from these simulations were analyzed using a Multi-Criteria Analysis (MCA), considering various indicators that influence the decision-making process. The wastewater quality assessment revealed that the wastewater generated in the three islands produced low concentrations of chemical and biological oxygen demand (COD and BOD), with concentrations ranging from 267 – 309 mg/L and 128 – 219 mg/L, respectively. Nitrate and phosphate concentrations were also low (5.7 – 18.0 mg/L and 2.8 – 14.9 mg/L, respectively), where these concentrations in Dhidhdhoo and Hoarafushi were already within the maximum allowable limits of 15 mg/L and 10 mg/L, respectively, for discharge into the deep sea. Based on the findings, secondary treatment technologies such as membrane bioreactors (MBR) and sequencing batch reactors (SBR) with Ultraviolet (UV) disinfection were found to be the most feasible options for treating the wastewater. These results were further checked for robustness using a sensitivity analysis. This study demonstrates that the proposed methodology is suitable for technology selection and can provide valuable information for policymakers and stakeholders in the country and serve as a basis for future studies.