Pollution and its mitigation by natural wastewater treatment systems linked to agriculture/aquaculture and conservation of biodiversity in selected ecologically valued areas in Thailand and Sri Lanka | |
| Author | Sriyani, Wickramasinghe M. |
| Call Number | AIT Diss. no.EV-09-06 |
| Subject(s) | Constructed wetlands--Thailand Constructed wetlands--Sri Lanka Biodiversity conservation Sewage--Purification--Biological treatment |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-09-06 |
| Abstract | Many remnant mangroves are forced to act as an informal multi-functional pollution mitigation zones and also serve as conservation and nature education areas. Efficient mineralization of nutrients from multiple sources by engineered and hydraulically contained zones in the mangrove soil makes it possible to retain the natural status and maintain a healthy biodiversity in these systems. Long-term data are presented for the high-profile urban mangrove reserves acting as pollution mitigation zones in Thailand (Bang Pu Nature Reserve - BPNR) and Sri Lanka (Kadolkele Nature Reserve - KNR). Two semi-engineered mangrove sites in Thailand and Sri Lanka dominated by Avicennia marina forest, received piggery and municipal wastewater, respectively. The wastewater quality was assessed by standard physico-chemical methods (TOC, P04-3 -P and N¬species). FISH, PCR and DNA sequencing were performed simultaneously to characterize the major underlying microbial groups. Results demonstrated that the mangrove can act as a vegetative buffer zone between natural and human environment with significantly higher efficiency than was previously reported. The hypemutrified treatment zone was well performed as removal of nutrients. The enhancement zone, an interface area between treatment zone and natural area fed with additional nutrients was characterized by an enhanced primary productivity. Potential nitrogen removal mechanisms were proposed for the based on the detected presence of bacterial and archaeal nitrifiers, anammox bacteria and denitrifiers. The obtained taxonomic identities of 16S rDNA clones were found to be critically novel for mangrove soil. The significant presence of anammox bacteria (Candidatus Scalindua sp.) and archaeal ammonia-oxidizers (Crenarchaeota) were reported for the first time. The first reported microbial community structure of nitrogen-cycling species and larger taxa (Nitrosomanas, Nitrobacter and Nitrosospira) did not vary substantially between natural and hypemutrified soil. Though portion of nutrients was absorbed by mangrove trees, the data indicated that the main nitrogen removal occurred through bacterial and archaeal nitrification, conventional denitrification, and anammox process. The supply of additional nutrients to the treatment and enhancement zone increased the diversity and abundance of phytoplankton growth. Significant phytoplankton diversity was observed in the enhancement zones (H' = 2.6) compared to that of the treatment zone (H' = 2.2) and the natural area (H' = 2.4). The area contained 15 crabs (Brachyura) and 5 mudskippers (Oxudercinae) species, major and critically important faunal groups, exhibited stability in terms of diversity and abundance under the long term pollution pressure. Leaf Area Index (LAI), Normalized deferential vegetation index (NDVI) and woody biomass were the indicators of the physiological states of mangrove trees. Results demonstrated that the LAI and NDVI values were lower in the stressful treatment zone but higher in enhancement zone, indicated the healthy state of vegetation. The positive response of the taxa to the nutrient enrichment was in line with their ecological characteristics. Serving to determine ecologically safe eutrophication limits, the case also suggests that a successful rehabilitation of an urban mangrove to its near natural state is feasible and a controlled addition of nutrients may even playa role facilitating it |
| Year | 2009 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-09-06 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Shipin, Oleg |
| Examination Committee(s) | Preeda Parkpian ;Tripathi, Nitin Kumar ;Vivarad Phonekeo |
| Scholarship Donor(s) | World Bank ;IRQUE project ;Rajarata University of Sri Lanka |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2009 |