Nutrient recovery from process water of hydrothermal carbonization process | |
| Author | Suwal, Sama |
| Call Number | AIT Thesis no.EV-17-20 |
| Subject(s) | Carbonization Sludge disposal |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. EV-17-20 |
| Abstract | Lack of proper faecal sludge (FS) management practices especially in developing countries is a serious hazard to the environment as well as public health. Hydrothermal carbonization (HTC) is an innovative technology, which can be employed for the treatment and management of FS by converting it into a valuable solid product called "hydrochar". Process water (PW) is the nutrient rich liquid by-product produced during the HTC process. This study evaluated the recovery of nitrogen (N) from PW through reduced pressure distillation-acid absorption process and chemical precipitation as magnesium ammonium phosphate (MAP). The PW was collected from HTC experiments conducted in a 1-L high-pressure reactor operated at temperature (T) and time duration (t) of 220°C and 5 h, with a feedstock of FS and rice husk (1:1). After HTC, 47.6 % of initial total nitrogen (TN) content of feedstock was retained in PW. The effects of different process parameters such as pH, T and t on N-removal and N-recovery efficiencies were determined. T and t were found to have significant effect on N-removal and N-recovery. The optimum operating conditions were determined to be at pH, T and t of 11, 55 °C and 60 min respectively. At these conditions, about 53.35 % of the N could be recovered as (NH4)2SO4, which can be utilized as an agricultural fertilizer. The chemical precipitation of MAP in raw PW and nitrogen recovery solution (N-RS) from reduced pressure distillation-acid absorption process showed N-recovery of 64.62 % and 82.67 % respectively as corroborated by SEM and XRD analysis. The cost analysis showed the reduced pressure distillation-acid absorption and chemical precipitation processes to have unit cost per 1 g N, at 3.37 and 5.02 Baht respectively, which is higher than the unit cost of commercial fertilizer. Bio-availability of the produced N-RS and MAP salts were tested on maize and lettuce plants under hydroponic growth conditions. Crop productivity and bio-availability were found to be highest for MAP salts from precipitation of N-RS. In the PW remaining after N-recovery, sugar and VFA content were found to be retained and concentrated. The possibility of further fermentation of sugar, extraction of VFAs and use of remaining PW as anaerobic digestion substrate was identified. |
| Year | 2017 |
| Type | Thesis |
| 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 (EV) |
| Chairperson(s) | Thammarat Koottatep; |
| Examination Committee(s) | Chongrak Polprasert;Annachhatre, Ajit P.; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2017 |