Indirect assessment of biomass accumulation in a wastewater-based Chlorella vulgaris photobioreactor by pH variation

Abstract

Algae bloom in coastal waters is partly supported by residual nutrients in treated wastewater (WW) released from coastally located treatment plants. In response, a Chlorella vulgaris-based photobioreactor was recently proposed for lowering nutrient levels in WW prior to release. However, the solution requires maintaining biomass accumulation to within a photobioreactor capacity for optimum operation. For high density Chlorella vulgaris suspensions, this is easily done by monitoring turbidity increase, a property directly related to biomass accumulation. For low density suspensions however, direct turbidity measurement would require a cumbersome process of concentrating large volumes of Chlorella vulgaris suspensions. Here, we demonstrate that by measuring pH of the suspensions, turbidity (T) can be estimated indirectly by the following wastewater-dependent expression: pH = aT + pH0, hence avoiding the need to concentrate large volumes. The term pH0 is the initial pH of the suspensions and a, a wastewater-dependent constant, can be computed independently from a = − 0.0061*pH0 + 0.052. In the event %WW is unknown, the following wastewater-independent Gaussian expression can be used to estimate T: pH = 8.71*exp(− [(T − 250)2]/[2*1.26E05]). These three equations should offer an avenue for monitoring the turbidity of dilute Chlorella vulgaris suspensions in large, stagnant municipal Chlorella vulgaris-based wastewater treatment system via pH measurements.

Iron-dependent mutualism between Chlorella sorokiniana and Ralstonia pickettii forms the basis for a sustainable bioremediation system

“…C. sorokiniana changed the pH of the neutral BBM to 7.9, suggesting a pH regulation due to algal photosynthesis. This increase in pH has been linked to the consumption of CO 2 and the nitrate metabolism in closed and stationery phototrophic culture conditions [ 64 ].…”

Harmful algae blooms: an analysis of recent spatiotemporal trends on California's inland waterbodies

“…[1][2][3] By releasing toxins into the environment, causing hypoxia in water and blocking sunlight needed for respiration in living systems, their potential impacts are broad and include causing injuries to human beings and ecological systems. [4][5][6] There are numerous examples to illustrate the negative consequences of HABs occurrence in water. For instance, a once crystalline lagoon in the Mediterranean Sea which is now choked with cyanobacteria because of characteristics alteration by pollution from farming related activities has been turned into a perpetual site of massive sh die-offs.…”