Monitoring and removal of natural organic matter (NOM) from Toowoomba water sources

McIntyre, Jamie (2015) Monitoring and removal of natural organic matter (NOM) from Toowoomba water sources. [USQ Project]

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Abstract

Natural organic matter (NOM), present in all water sources, proves problematic for the water treatment industry due to its reaction with disinfectants, particularly chlorine. This reaction forms allegedly harmful, carcinogenic disinfection by-products. There are no regulatory limits in place in Australia for the quantifiable NOM surrogate parameter of organic carbon. Few studies have been conducted in Australia with the aim of quantifying the amount of NOM in water sources, with none having been conducted to investigate Toowoomba water sources.

The aim of this dissertation was to investigate the amount of organic matter in certain water sources of Toowoomba, the removal of this by enhanced coagulation, and the trihalomethane formation potential of each of the water sources before and after treatment. The methodology used to achieve this involved the collection of water samples from four water sources, three of which are drinking water sources for the Toowoomba region treated by the Mt Kynoch Water Treatment Plant. The water sources include the Japanese Gardens, Cooby Dam, Perseverance and Cressbrook Dams, and a raw water mixture of the blended raw water sources collected immediately prior to treatment from the Mt Kynoch Water Treatment Plant. Water samples were collected weekly for a ten-week period for the purpose of measuring the pH, turbidity, conductivity, total dissolved solids, alkalinity, dissolved organic carbon, ultraviolet absorption, iron and certain anions. Additional water samples were collected to conduct jar tests to investigate the removal of the organic carbon by enhanced coagulation. The jar tests were performed with alum as the coagulant being added in 10 mg/L increments up to 100 mg/L. Trihalomethane formation potential testing was also carried out.

In the absence of any Australian regulatory limits for organic carbon or treatment techniques, all experimental results for the Toowoomba water sources have been compared to the standards and practices in place in the United States.

Experimental results revealed the average dissolved organic carbon concentrations to be 4.51 mg/L, 7.29 mg/L, 5.75 mg/L and 5.26 mg/L for the Japanese Gardens, Cooby Dam, Perseverance Dam and the Mt Kynoch mixture respectively. Each of these values is greater than 2.0 mg/L, used in the United States as the trigger for the implementation of further treatment. If the organic carbon concentration of a raw water source exceeds this value, further treatment in the form of enhanced coagulation must be implemented. Therefore, it is recommended that further treatment is necessary for these Toowoomba water sources to target the removal of the excessive organic carbon present, in accordance with the regulations in place in the United States.

Jar test results demonstrated a decreasing trend in turbidity and dissolved organic carbon measurements with the increasing addition of alum. Optimum coagulant doses were selected based upon methods of analysis which involved identifying the point of diminishing return for each of the water sources. The optimum coagulant doses of alum selected were: 70 mg/L for both the Japanese Gardens and Perseverance and Cressbrook Dams water sources; 90 mg/L for the Cooby Dam water source; and 60 mg/L for the Mt Kynoch raw water mixture. Treating the water sources with these alum doses resulted in organic carbon removal percentages of 36.2 percent, 33.1 percent, 32.0 percent, and 37.8 percent respectively. These jar tests were replicated to verify the results.

Equations were developed for each water source to theoretically predict the residual organic carbon from the coagulant dose. When treating the water samples with the selected optimum coagulant doses, the predicted residual organic carbon concentrations left untreated are 2.41 mg/L, 4.42 mg/L, 3.91 mg/L and 4.34 mg/L for the Japanese Gardens, Cooby Dam, Perseverance and Cressbrook Dams, Mt Kynoch raw water mixture water sources respectively.

The trihalomethane formation potential of the untreated water samples were measured to be: 132 ppb for the Japanese Gardens water; 209 ppb for the Cooby Dam water source; 250 ppb for Perseverance and Cressbrook Dams; and 231 ppb for the Mt Kynoch raw water mixture. Treating these water samples with the selected optimum coagulant dosages reduced the trihalomethane formation potentials to 22 ppb, 91 ppb, 146 ppb and 82 ppb respectively.

This research has contributed to quantifying the natural organic matter within Toowoomba’s water sources, and investigating the removal of this by enhanced coagulation. Further research is recommended to better understand in more detail the topics covered by this dissertation.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours) (Environmental) project
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying
Supervisors: Aravinthan, Vasanthadevi
Date Deposited: 07 Jun 2016 04:50
Last Modified: 07 Jun 2016 04:50
Uncontrolled Keywords: Water quality, Organic matter, Enhanced coagulation
Fields of Research : 09 Engineering > 0907 Environmental Engineering > 090703 Environmental Technologies
URI: http://eprints.usq.edu.au/id/eprint/29289

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