UBC Theses and Dissertations
A lysimeter study of domestic waste water renovation by forest soil filtration Khor, Chin Choon
Laboratory lysimeters were used to investigate the behaviour, over time, of a humid west coast forest soil under intermittent primary municipal waste water irrigation. Mineral soil packed to a depth of 69 cm and to a uniform density of about 0.9 gm per cm³ was covered with a forest floor 9 cm thick. Sintered glass bead tensiometers were used to gauge the water potential distributions in the soil lysimeters. Irrigation and drainage systems were designed to maintain constant rates of waste water application and facilitate measurement of drainage rates. Two groups of soil lysimeters each with triplicate samples, were loaded with waste water at the rates of 0.23 cm per day ( 37 cm³ per day ) and 0.47 cm per day ( 75 cm³ per day ) for a period of 9 months. The soil lysimeters were incubated at a temperature of about 15.5 degrees Centigrade. The total amounts of nitrogen added to both groups of soil lysimeters were 223.7 gm and 436.9 gm or equivalent to 1.4 % and 2.7 % of the total nitrogen of the original soil, respectively. Renovations of wastewater in terms of nitrogen were 75 % and 43 % with respect to the two groups of soil lysimeters. Renovations in terms of phosphorus were more than 99 % in both groups of soil lysimeters. Retention of nutrients by the soil was increased with time under favourable aerobic conditions. Uptake of nutrients by vegetation in the field would minimize leaching losses. Results from this experiment indicated no significant changes in the physical and chemical behaviour of the soils. Proper design of the waste water irrigation system in terms of loading would maximize the efficiency of renovation without deteriorating the behaviour of the soils.
Item Citations and Data