Performance Of High Rate Algal Ponds Research Articles

Microalgae-based wastewater treatment for micropollutant removal in swine effluent: High-rate algal ponds performance under different zinc concentrations

Despite the social and economic importance of swine farming, this activity has great polluting potential due to the large wastewater generation composed of high micropollutant concentrations, such as trace metals (Zn and Cu). Microalgae can integrate the solutions to overcome these challenges by obtaining value-added biomass, closing the loop for an environmentally and economically sustainable wastewater treatment technology. Therefore, this study aimed to identify the interference of different Zn concentrations (0.5 to 70 mg/L) in SW on the performance of high-rate algal ponds considering real treatment and biodegradation conditions via microalgae. The innovative results showed that N-NH4+ removal was compromised with high Zn concentrations due to nitrification inhibition. Oppositely, the removal of soluble P was enhanced under conditions that favored algal growth (40 and 55 mg Zn/L). Moreover, Zn conferred an increase in soluble chemical oxygen demand that changed from 190 mg/L at the beginning of the treatment to 624 mg/L at the end due to extracellular polymeric substances production. Sequential chemical extraction demonstrated that biomass growth had an important contribution to Zn removal; however, it did not exceed the contribution of carbonates (28.7–44.2 %). The biomass characterization showed that Zn did not significantly affect the levels of proteins (41.2–53.5 %) and carbohydrates (34.0–43.5 %), while the lipids content was higher (18.2 %) in 55 mg Zn/L. The effects of Zn on nutrient removal and the biomass's biochemical composition must be pondered to combine the recovery of metals and nutrients and the production of value-added biomass.

Effect of Paddle-Wheel Pulsating Velocity on the Hydrodynamic Performance of High-Rate Algal Ponds

AbstractHigh-rate algae ponds (HRAPs) are widely used in increasing biofuel production because of their effective design in terms of cost and power consumption. Using modeling and simulation techniques is an economical approach for improving the design of raceways. Previous modeling studies reported the use of a flat velocity profile, thus failing to depict the real phenomena involved. However, in practice, the rotating paddle wheel in HRAPs produces a pulsating velocity that is necessary for culture growth. In this study, the hydrodynamic characteristics of algal ponds were investigated using a coupling algorithm to map the effects of a two-dimensional paddle wheel on a three-dimensional raceway model. HRAPs with and without paddle wheels were compared in terms of hydrodynamic mixing, dead zones, and power consumption. The results revealed that compared with a flat velocity at the inlet, the pulsating velocity of a paddle wheel produced a large dead zone volume with reduced power consumption, shear stres...

Control of algal production in a high rate algal pond: investigation through batch and continuous experiments.

For decades, arid and semi-arid regions in Africa have faced issues related to water availability for drinking, irrigation and livestock purposes. To tackle these issues, a laboratory scale greywater treatment system based on high rate algal pond (HRAP) technology was investigated in order to guide the operation of the pilot plant implemented in the 2iE campus in Ouagadougou (Burkina Faso). Because of the high suspended solids concentration generally found in effluents of this system, the aim of this study is to improve the performance of HRAPs in term of algal productivity and removal. To determine the selection mechanism of self-flocculated algae, three sets of sequencing batch reactors (SBRs) and three sets of continuous flow reactors (CFRs) were operated. Despite operation with the same solids retention time and the similarity of the algal growth rate found in these reactors, the algal productivity was higher in the SBRs owing to the short hydraulic retention time of 10 days in these reactors. By using a volume of CFR with twice the volume of our experimental CFRs, the algal concentration can be controlled during operation under similar physical conditions in both reactors.

Algal biomass production and wastewater treatment in high rate algal ponds receiving disinfected effluent

Algal biomass production associated with wastewater is usually carried out in high rate algal ponds (HRAPs), which are concomitantly used in the treatment of such effluent. However, most types of wastewater have high levels of bacteria that can inhibit the growth of algal biomass by competing for space and nutrients. The objective of this study was to assess the influence of ultraviolet (UV) pre-disinfection on the performance of HRAPs used for wastewater treatment and algal biomass production. Two HRAPs were tested: one received effluent from an upflow anaerobic sludge blanket (UASB) reactor – HRAP – and the second received UASB effluent pre-disinfected by UV radiation – UVHRAP. Physical, chemical and microbiological parameters were monitored, as well as algal biomass productivity and daily pH and dissolved oxygen (DO) variation. The UVHRAP presented highest DO and pH values, as well as greater percentage of chlorophyll a in the biomass, which indicates greater algal biomass productivity. The average percentages of chlorophyll a found in the biomass obtained from the HRAP and the UVHRAP were 0.95±0.65% and 1.58±0.65%, respectively. However, total biomass productivity was greater in the HRAP (11.4 gVSS m−2 day−1) compared with the UVHRAP (9.3 gVSS m−2 day−1). Mean pH values were 7.7±0.7 in the HRAP and 8.1±1.0 in the UVHRAP, and mean values of DO percent saturation were 87±26% and 112±31% for the HRAP and the UVHRAP, respectively. Despite these differences, removal efficiencies of organic carbon, chemical oxygen demand, ammoniacal nitrogen and soluble phosphorus were statistically equal at the 5% significance level.