The flower and the butterfly constructed wetland system at Koh Phi Phi—System design and lessons learned during implementation and operation

Abstract

a b s t r a c tIn 2007, a constructed wetland system was implemented on the tourist island of Koh Phi Phi in Southern Thailand. This paper presents the process of planning, designing and implementing the system and discusses the performance and operational issues 3 years after implementation. The system is an international lighthouse project showing the potential for aesthetical integration of constructed wetland systems in the built environment. The system comprises a wastewater collection system for the main business and hotel area of the island, a pumping station and a pressure pipe system to the treatment facility, a multi-stage constructed wetland system, and a system for reuse of treated wastewater. The treatment chains consist of vertical-flow, horizontal subsurface flow and free water surface flow units. Because the treatment system is located at the centre of the island, surrounded by resorts, restaurants and shops, the systems are designed with terrains as scenic landscaping. The wastewater is treated to meet the Thai effluent standards for total suspended solids and nitrogen, but because of inadequate pre-treatment and removal of oil and grease prior to the system, the standards for oil and grease and BOD are not met. A number of challenges during construction and operation have caused problems with clogging of the vertical flow constructed wetlands and given rise to odour problems. Safeguards were prepared, but not effectively activated, mainly because no key-person or key-authority took responsibility for managing the system.

Domestic Wastewater Treatment

“…HTWs require smaller unit area and secure higher efficiency of pollutants removal in comparison to one stage systems. The hybrid designs incorporating multiple stages of TWs is now becoming more popular (Gómez Cerezo et al 2001;Peng et al 2005;Brix et al 2011;Vymazal and Kropfelova 2011) due to the higher tolerance and efficiency of this kind of systems from one side and the often lower footprint in comparison to single stage ones when facing flow and loads variations, or even for giving chances of different outflows quality to be chosen on seasonal basis and depending on the required final concentration of pollutants. Furthermore, single typology TW systems have intrinsically specific limits in terms of processes which occur inside the reactors, for example the commonly scarce nitrification for the HSSF systems or the low denitrification rate for the VSSF unsaturated systems.…”

Multifunctional Wastewater Treatment Landscapes

“…The park program features a pavilion, turf areas, large panels of fl owering plants, seating and strolling areas, and a small sports fi eld. In addition to these social, recreational, and aesthetic amenities, water from the treatment wetland system is captured in a reservoir for irrigation of the park (Brix et al 2011).…”

“…The treated water fl ows into a 0.71m deep linear polishing pond containing 200 m 2 of open water to remove nutrients. The effl uent is treated to tertiary standards and then fl ows into a closed reservoir for use in irrigation (Brix et al 2011).…”

“…The project cost $700,000 (2006 dollars). A local contractor constructed the project using island residents for labor (Brix et al 2011).…”

Phytoremediation

“…Brix et al ( 2011 ) describe a full-scale system built in Thailand incorporating a multistage constructed wetland. The system was designed for the treatment of 400 m 3 / day of wastewater from a business and hotel area.…”