Measuring the Concentration of Three Microalgae Using Self-Made Turbidimeter
Date Issued
2010
Date
2010
Author(s)
Wu, Shang-Rong
Abstract
Micro-algae have long been important ingredients of health food. In addition, considerable amount of lipid in their cells is found to be a promising source of bio-diesel fuel, therefore ever-increasing budget has been put into micro-algae culture industry in recent years.
Nevertheless, given that recording and monitoring concentration of suspending cells remain tasks performed manually, both laborious and time-consuming, the ideal goal of automated micro-algae production would be arduous to achieve.
Monoculture is the typical way adopted in micro-algae culturing, as such, turbidity is a suitable indicator in evaluating cell density of an alga-suspension. Although several kinds of turbidimeters have been available in practical use, most of them mandate repeated samplings that are inconvenient in a budget-limited, field-based, full-time monitoring program. With the handheld turbidimeter entering the market, such impediment seemingly would no longer exist, not only does it simplify routine monitoring by omitting the necessity of repeated samplings but it also can provide instantaneous and less interrupted recording data.
In this study, several inexpensive, sturdy and ready-made components including TBS-200 Turbidity sensor(Solteam Opto. Co.), Analog-to-Digital Convertor(ADC), LCD module, Microcontrolling Unit(MCU) etc, are used to assemble a low-cost prototype of handheld turbidimeter. The possible disturbance of ambient light and its effect on output electric resistance of the turbidity sensor are especially taken into account on experiment designing. The prime cost of such a workable handheld turbidimeter is less than 2000 NT dollars.
Three species of micro-algae with economic potential, including Tetraselmis, Isochrysis and Haematococcus are selected in our study. In addition to cell counts determined under microscopic examination and net weight obtained from desiccated alga mass, the turbidity data measured repectively by laboratory turbidimeter HACH 2100N and our prototype turbidimeter are compared in order to assess feasibility of the latter in monitoring micro-algae concentration.
The results reveal that to eliminate the disturbance caused by ambient light the sensor of our prototype handheld turbidimeter must be operated in a black sampling bottle. The coefficient of variation of readings is less than 10% when the turbidity is more than 50 NTU. Different grain sizes of various micro-algae species also have a remarkable influence on turbidity readings. Our prototype handheld turbidimeter shows a consistently lower reading value than that of HACH 2100N.
Analysis between turbidity readings and cell counts with quadriatic regression manifests a positive correlation, the R2 value for three micro-algae species are : Tetraselmis 0,99; Isochrysis 0.983; Haematococcus 0.976. The R2 value for turbidity and net weight are: Tetraselmis 0,937; Isochrysis 0.981; Haematococcus 0.963. These results support the conclusion that our prototype handheld turbidimeter could be a useful tool to promptly evaluate the concentration of single-species microalgae.
Subjects
Turbidimeter
Micro-algae
Micro-controller
Low-cost
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