IMPROVEMENTS ON MUNICIPAL WASTEWATER TREATMENT BY: CHEMICAL PRE-PRECIPITATION WITH CA2+ & MG2+ AND ACID HYDROLYSIS OF TOILET PAPER
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
The present municipal wastewater treatment technology is very much in need of two main ingredients; economizing the treatment system through self sustained products such as energy and nutrients recovery, as well as improving cleaning results to compete with the increasing demands on the plants with ever more stringent discharge standards. The thesis study therefore aims on improving the present wastewater treatment technology concentrating on the recovery of an increased amount of energy as well as nutrients with the objectives or treatment concepts; chemical pre-precipitation using the novel chemicals combination calcium (Ca2+) and magnesium (Mg2+) together, and the use of acid hydrolysis of toilet paper for producing an internal carbon source to replace the external carbon source requirement at post-anoxic denitrification process. In addition, since the author is from Sri Lanka; which has large unrealised potential sources of cheap supply of chemicals calcium and magnesium from the local industries, limestone industry and solar evaporated salt production, the feasibility of integrating this novel treatment technology (chemical pre-precipitation using Ca2+ and Mg2+) to these industries is evaluated, to achieve an economical treatment system.
The thesis study consists of two main experimental analyses for chemical pre-precipitation and acid hydrolysis. Chemical pre-precipitation of primary effluent from Hammarby Sjöstadsverk had been done using the chemicals Ca2+ and Mg2+ as in Ca(OH)2 and MgCl2 within the concentrations range, 10-30 mg/l for Ca2+ and 10-40 mg/l for Mg2+ with measurements done on percentage reductions of COD, total phosphorus and total nitrogen, and percentage increases of conductivity and alkalinity. Acid hydrolysis study of toilet paper was carried out with one basic experiment, using a sulphuric acid solution of pH 2, and using around 10 mg of toilet paper; where the COD of the solution was measured after a specific retention time. The feasibility evaluation of the integration of local Sri Lankan industries to the particular novel wastewater treatment technology was done following a literature analysis as well as by means of the authors’ experience and knowledge on the aspects, obtained by living in Sri Lanka for over twenty six years.
The results of the experimental study on chemical pre-precipitation with Ca2+ and Mg2+ have been discussed for; the deviations when observed over the expected results and the possible causes as well as the suggestions for improvements, while comparisons for the other conventional solutions and similar processes were done. For acid hydrolysis of toilet paper, the obtained results have been discussed in terms of the potential to be used in post-anoxic denitrification process. The pros and cons of these alternatives are also discussed in brief. The integration of the local Sri Lankan industries to the wastewater treatment was also discussed assessing the present context and potential of expansion of these chemicals industries. A brief cost evaluation was also done comparing the study focuses against other common and conventional solutions. In addition, several recommendations for future studies have also been offered, to continue or to improve the study focuses.
Place, publisher, year, edition, pages
2011. , 61 p.
Trita-IM, ISSN 1402-7615 ; 2011:27
calcium, magnesium, chemical pre-precipitation, COD, total nitrogen (Tot-N), total phosphorus (tot-P), acid hydrolysis, toilet paper
IdentifiersURN: urn:nbn:se:kth:diva-108291OAI: oai:DiVA.org:kth-108291DiVA: diva2:579552
Subject / course
Master of Science - Sustainable Technology
Persson, Per Olof, Senior lecturerHultman, Bengt
Persson, Per Olof, Senior lecturer