73 The use of algae to treat wastewater in the berkeley pit

Abstract

The Berkeley Pit in Butte, Montana is currently filled with 35 billion gallons of water, with 6 million gallons being added daily. The water in the pit contains a number of dissolved metals and other elements. These elements include: aluminum, iron, manganese, zinc, copper, cadmium, magnesium, nickel, calcium, sulfur, and silicon. Also, over 40 different types of small organisms live in the contaminated water. The purpose of this experiment is to examine the uptake potential of elements from Berkeley pit water by highly concentrated algal samples. The algae used are called Chlamydomonas acidophila. Chlamydomonas acidophila's optimum pH is between 3.5 and 4.5 and it may be capable of metal uptake by two mechanisms: absorption and adsorption. Adsorption and absorption are good alternatives to traditional wastewater treatments because algal cells are a naturally abundant renewable resource that can be cheaply produced. Algal cells are also highly selective in terms of removal and recovery of specific heavy metals, they do not require reagents, which typically cause disposal and space problems, and they require a relatively low initial capital investment with low operating costs. The experimental procedure involved using modified acid medium to grow algae from a stock solution to a concentration of 1.6×108 algae cells/mL. The growth medium was then washed from the algae cells. Three initial samples of sterile filtered pit water (SFPW) were set aside as a control. Then, concentrated algae cells were added to three centrifuge tubes. Next, SFPW was added to 3 tubes with algae and three tubes without algae. After 1 hour, a 5 mL sample was taken from each of the centrifuge tubes. After 24 hours, another 5 mL sample was taken from each of the centrifuge tubes. Inductively Coupled Plasma (ICP) analysis was performed on all the samples. The results from the initial SFPW were compared with those samples containing algae for 1 hour and 24 hours. Total metal uptake in 24 hours was roughly 7.81%.