This thesis is composed of two studies. The first study is done to prove the premise that both alkalinity and hardness affect on the dissolved phosphorus concentration so that the growth of algae is also affected in water bodies like rivers and lakes....
This thesis is composed of two studies. The first study is done to prove the premise that both alkalinity and hardness affect on the dissolved phosphorus concentration so that the growth of algae is also affected in water bodies like rivers and lakes. Statistical analysis of the water quality data of 13 reservoirs collected for the last decade shows the relations between alkalinity and chlorophyll-? and between hardness and chlorophyll-? are not linear but follow second order equation. This relation seems to be due to two antagonistic effects accompanying a simultaneous increase in alkalinity and hardness. The increase stimulates the growth of algae by supplying carbonates and to algae and at same time it causes a decrease in soluble phosphorus which retards algae to grow. These opposing tendencies are confirmed by theoretical calculations with the MINTEQ model. There seems to be ranges of alkalinity and hardness that are in favor of algae growth; the ranges are less than 44 mg/L as in alkalinity and also less than 63 mg/L as in hardness. This finding will provide a solid base to develop an effective water quality management of water bodies.
The second study is done to find chemicals adequate to control alkalinity and hardness in order to reduce dissolved phosphorus in water bodies like rivers and lakes. Five chemicals are selected for the study: calcite, lime, dolomite, magnesite, and gypsum. Data are obtained from the calculations with MINTEQ model as a function of dosage variations of each chemical. Findings are as follows: Three out of the five chemicals are found to be effective in reducing the dissolved phosphorus, i.e., calcite, lime, and dolomite. Calcite and dolomite are able to lower the phosphorus concentration up to one thousandth fold whereas lime does one hundred thousandths fold. In viewpoint of pH variation, both calcite and dolomite seem to be safe since the pH does not increase over 8.3 even in case of overdose. In the same circumstance, with lime the pH increases beyond 9 which is considered to be the highest pH level for the protection of water ecosystem. Nevertheless it is recommendable to use lime in case where there are some difficulties in water quality control due to algae blooms.