Modeling greenhouse gas emissions from combined sewer systems | |
| Author | Thitirat Chaosakul |
| Call Number | AIT Diss. no.EV-14-04 |
| Subject(s) | Greenhouse gas mitigation--Thailand Combined sewers--Thailand |
| Note | A dissertation submitted in fulfillment of the requirements for the degree of Doctor of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-14-04 |
| Abstract | Most drainage sy stems in developing countries are gravity - flow combined sewers which receive stormwater and effluent from septic tanks or cesspools of households and buildings. Problems associated with such sewers include pollutant contamination entering rivers and ground water , odor of methane gas (CH 4 ), emissions of greenhouse gas especially CH 4 , and solid accumulation. S tagnancy of wastewater and solid sediment in the sewers of developing countries was believed to be the single most significant source of CH 4 . Barriers to developing urban management, improving water quality and implementing best management practices for these drainage systems include a lack of understanding about sediment dynamics and CH 4 emission model ing associated with tropical climate. Mod e ling CH 4 produc tion and emission associated with a gravity - flow combined sewer in the tropical monsoon climate of Thailand was done . To quantify and develop models for predicting CH 4 production and emission, a p ilot - scale experiment and field investigations were conducted to understand the hydraulic behaviour and the interaction of oxygen transfer rate in wastewater with different hydraulic conditions . A mathematical model and an empirical model were developed to predict CH 4 emission (CH 4(g) ) f rom wastewater sewers . The mathematical model w as developed from a pilot scale hardware model consisting of a 10 - m long cement pipe with an inner diameter of 10 cm and slopes adjustable between 0.0005 to 0.002 which was installed outdoors at the Environmen tal Research Station of AIT and validated with field survey data of gravity - flow sewers located in a peri - urban area, central Thailand. The empirical model w as developed from field survey data of gravity - flow sewers located in a peri - urban area, central Th ailand and validated with field data of a sewer system of the Gold Coast area, Queensland, Australia. Sediment dynamics were determined to understand the characteristics of sediment, build - up and washoff rates to help support appropriate planning and manag ement practices for the drainage systems and potentially as a means to manage CH 4 emission. Results showed that the f actors which affected CH 4 emiss ion included w astewater characteristics, hydraul ic conditions and sediment deposits , flow rate (Q), dissolved oxygen (DO), surface area to volume ratio (A/V) of sewer, hydraulic retention time (HRT) and wastewater temperature , as determined by direct measurements in a test sewershed for a peri - urban area , Rattanakosin Village, central Thai land . The models reflected dry weather conditions reasonably well but still need more data to improve the model accuracy and the prediction modeling for wet weather flow . Based on field investigations, sediment build - up rates, washoff rates, and size chara cteristics appear to depend on land use. Results showed that maximum build - up rates were 12.9, 21.5 and 41.3 g/m - curb/d, while the washoff rates were 13.8, 167.3 and 1,471 g/L/s in residential, commercial and industrial areas , respectively. The median diam eter (d 50 ) of street sediments ranged between 170 - 520 μm , where as an average of 1 - 9% was smaller than 75 μm. A personal computer vers ion of the Stormwater Management Model ( PCSWMM ) was applied in Rattanakosin Village using these empirically - determined build - up and washoff coefficients, which substantially improved the accuracy of model estimates as compared to the default model values . With respect to climate change concerns, t he estimated CH 4 emission of 1 3 5 Ton CO 2 - eq/yr based on field measurements from the sewer of Rattanakosin Village was higher than emission estimates based on IPCC guidelines of 80 Ton CO 2 - eq/yr but lower than the estimat e based on by US.EPA methods ( 265 Ton CO 2 - eq/yr ) . CH 4 from the sediments likely contributed 12 - 16% of the total CH 4 formation in sewers . Application of this model to improve urban management of gravity - flow sewers to minimize GHG production and reduce glob al warming wa s presented such as designing sewer slope to be at least 0.002 and maintaining the self - c leansing velocity in the sewers and r outine cleaning of the sewers to avoid excessive sludge accumulation |
| Year | 2014 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-14-04 |
| 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) | Thammarat Koottatep |
| Examination Committee(s) | Annachhatre, Ajit P. ;Babel, Mukand Singh ;Irvine, Kimberly Niel |
| Scholarship Donor(s) | The National Centre for Competence in Research (NCCR) North - South Project ;Royal Thai Government ;Asian Institute of Technology Fellowship |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2014 |