Harvesting of Chlorella sorokiniana BR001 cultivated in a low-nitrogen medium using different techniques

ABSTRACT: The harvesting process is a current challenge for the commercial production of microalgae because the biomass is diluted in the culture medium. Several methods have been proposed to harvest microalgae cells, but there is not a consensus about the optimum method for such application. Herein, the methods based on sedimentation, flocculation, and centrifugation were evaluated on the recovery of Chlorella sorokiniana BR001 cultivated in a low-nitrogen medium. C. sorokiniana BR001 was cultivated using a low-nitrogen medium to trigger the accumulation of neutral lipids and neutral carbohydrates. The biomass of C. sorokiniana BR001 cultivated in a low-nitrogen medium showed a total lipid content of 1.9 times higher (23.8 ± 4.5%) when compared to the biomass produced in a high-nitrogen medium (12.3 ± 1.2%). In addition, the biomass of the BR001 strain cultivated in a low-nitrogen medium showed a high content of neutral carbohydrates (52.1 ± 1.5%). The natural sedimentation-based process was evaluated using a sedimentation column, and it was concluded that C. sorokiniana BR001 is a non-flocculent strain. Therefore, it was evaluated the effect of different concentrations of ferric sulfate (0.005 to 1 g L-1) or aluminum sulfate (0.025 to 0.83 g L-1) on the flocculation process of C. sorokiniana BR001, but high doses of flocculant agents were required for an efficient harvest of biomass. It was evaluated the centrifugation at low speed (300 to 3,000 g) as well, and it was possible to conclude that this process was the most adequate to harvest the non-flocculent strain C. sorokiniana BR001.

The Potential Use of Nephelium lappaceum Seed as Coagulant–Coagulant Aid in the Treatment of Semi-Aerobic Landfill Leachate

Chemical-based coagulants and flocculants are commonly used in the coagulation–flocculation process. However, the drawbacks of using these chemical materials have triggered researchers to find natural materials to substitute or reduce the number of chemical-based coagulants and flocculants. This study examines the potential application of Nephelium lappaceum seeds as a natural coagulant–coagulant aid with Tin (IV) chloride (SnCl4) in eliminating suspended solids (SS), colour, and chemical oxygen demand (COD) from landfill leachate. Results showed that the efficiency of Nephelium lappaceum was low when used as the main coagulant in the standard jar test. When SnCl4 was applied as a single coagulant, as much as 98.4% of SS, 96.8% of colour and 82.0% of COD was eliminated at an optimal dose of 10.5 g/L and pH 7. The higher removal efficiency of colour (88.8%) was obtained when 8.40 g/L of SnCl4 was applied with a support of 3 g/L of Nephelium lappaceum. When SnCl4 was utilised as a coagulant, and Nephelium lappaceum seed was used as a flocculant, the removal of pollutants generally improved. Overall, this research showed that Nephelium lappaceum seed is a viable natural alternative for treating landfill leachate as a coagulant aid.

Ultrasonic Synthesis of Nanochitosan and Its Size Effects on Turbidity Removal and Dealkalization in Wastewater Treatment

A detailed study on the synthesis of chitosan nanoparticles under ultrasonication is reported in this paper. By using this simple technique, chitosan particles in nanometer range can be easily prepared without using any harmful and expensive chemicals. The results show that increasing the ultrasonic irradiation time and ultrasonic wave amplitude are the key factors for producing discrete chitosan nanoparticles with narrow particle size distribution. The resulting nanoparticles show superior turbidity removal efficiency (75.4%) and dealkalization (58.3%) in wastewater treatment than the bulk chitosan solid (35.4% and 11.1%, respectively), thus offering an eco-friendly and promising approach for treating wastewater via the coagulation/flocculation process.

Coagulation performance evaluation of alginate as a natural coagulant for the treatment of turbid water

Alginates are quite abundant in nature as they occur both as a structural component in marine brown algae (Phaeophyceae) comprising up to 40% of dry matter and as capsular polysaccharides in soil bacteria. Alginic acid is the only polysaccharide, which naturally contains carboxyl groups in each constituent residue, and possesses various abilities for functional materials. Experiments were carried out for the water of turbidity 300 NTU. Alginate as such doesn't act as a coagulant instead it should be converted to calcium alginate by adding calcium ions. Calcium chloride was used for imparting calcium ions necessary for the reaction. The dosage of calcium was fixed as 50 mg/L, 75 mg/L, 100 mg/L, 150 mg/L, 200 mg/L, and alginate doses between 2 to 10 mg/L. Calcium dosage below 50 mg/L was not sufficient enough for the formation of egg-box structure which is responsible for the coagulation and flocculation process. For the mechanism of charge neutralization to take place effectively, calcium should be added first followed by alginate. pH and conductivity of the sample remain constant before and after the treatment. The dosage of alginate required for the treatment is less so the cost of treatment also will be very less, thus alginate can replace the usage of chemical coagulants like alum.

Effect of the Recycling Process on Drinking Water Treatment: Evaluation Based on Fluorescence EEM Analysis Using the Peak-Picking Technique and Self-Organizing Map

The recycling process is applied in many water treatment plants (WTPs), although this process can lead to adverse effects. The effect of the recycling process on the characteristics of dissolved organic matter was evaluated based on a fluorescence excitation-emission matrix using the peak-picking technique and self-organizing map (SOM). In this study, an evaluation of two WTPs, one with and one without a recycling system, was carried out. Both WTPs show moderate efficiency during the coagulation–flocculation process in removing DOC, fulvic acid-like, humic acid-like, and tryptophan-like substances. The recycling process causes increased values of fulvic acid-like, humic acid-like, and tryptophan-like substances and specific ultraviolet absorbance (SUVA) after the filtration process of about 31.0%, 35.7%, 22.2%, and 6%, respectively. Meanwhile, the WTP without recycling showed a reduction in the level of fulvic acid-like, humic acid-like, and tryptophan-like substances and SUVA by 23.3%, 52.9%, 27.8%, and 21.1%, respectively. Moreover, SOM analysis based on the peak-picking technique can determine differences in sample clusters due to the recycling process.

Factorial optimization of Coagulation-Flocculation process for Abattoir Wastewater using Carica Papaya seed extract as bio-coagulant

The objective of this research was to optimize the coagulation-flocculation process for abattoir wastewater by utilizing a bio-coagulant derived from Carica Papaya seed (CPS). The bio-coagulant (CPC) was extracted from the Carica Papaya seed using a 2M NaCl solution, and the coagulation-flocculation process was carried out using a bench scale jar test. Applying design expert (13.0.5.0), 23 full factorials with 5 center points, the effects of three factors: coagulant dosage (X1), pH of the wastewater (X2), and temperature (X3) on turbidity reduction efficiency were examined. Applying ANOVA, it was discovered that a linear model best characterizes the process, with a significant p-value of 0.0015, showing that the model is significant. Additionally, the temperature is a significant component in the model, with a p-value of 0.02 indicating that the temperature is statistically significant. A turbidity reduction efficiency of 90.02 % was attained at the optimum conditions of 0.75g/L of CPC, pH of 6, and temperature of 308 K.

Polyvinylidene Fluoride Membrane with a Polyvinylpyrrolidone Additive for Tofu Industrial Wastewater Treatment in Combination with the Coagulation–Flocculation Process

Wastewater from the tofu industry contains many pollutants that are very harmful to the environment, significantly endangering aquatic life and producing a pungent odor. This study aims to prepare a polyvinylidene fluoride (PVDF) membrane with the additive polyvinylpyrrolidone (PVP), and utilize it to treat tofu wastewater in the ultrafiltration (UF) process. Flat sheet membranes were prepared using PVDF that was dissolved in N,N-dimethylacetamide (DMAc) and then combined with the additive material of PVP at the varying compositions of 14.9/0.1, 14.85/0.15, and 14.8/0.2 g of PVDF/gram of PVP. The addition of PVP was proposed to improve the properties of the membranes. Characterization by scanning electron microscope (SEM), water contact angle, and Fourier transform infrared spectroscopy (FTIR) were performed on the PVDF/PVP membrane flat sheet in order to understand and compare changes in the physical and chemical properties that occurred in the membrane. Prior to the UF process, the tofu wastewater was treated by a coagulation–flocculation process through a jar tester using poly aluminum chloride (PAC) as a coagulant. Based on the membrane characterization, the addition of PVP improved the physical and chemical properties of membranes. The pore size of the membrane becomes larger, which could increase permeability as well as the flux value. The TSS and turbidity of the water produced in the UF process decreased with an increase in feed pressure due to a greater driving force generated to facilitate the penetration of the suspended solids. The UF results showed that the effect of PVP on water flux was greatest for the 14.85/0.15 PVDF/PVP membrane for both pure and wastewater. In addition, the highest percentage of rejection for TSS and turbidity were observed in the 14.9/0.1 PVDF/PVP membrane and rejection for TDS was indicated in the 14.8/0.2 PVDF/PVP membrane. Meanwhile, the resulting pH decreased slightly across all samples as feed pressure increased.

Effectiveness of Mushroom (Pleurotus Pulmonarius) Waste as Natural Coagulant for Kaolin Synthetic Water via Coagulation-Flocculation Process

Coagulation-flocculation process is a widely used method in water treatment. In this study, mushroom waste was selected as natural coagulant to treat kaolin synthetic water via coagulation-flocculation process. Rotten mushroom and mushroom spent were evaluated separately. Functional group of mushroom wastes were analyzed using Fourier Transform Infrared Spectroscopy. Optimum dosage and pH of mushroom wastes and aluminium sulphate in kaolin synthetic water treatment were examined through jar testing. A comparative study on the effectiveness of mushroom wastes and aluminium sulphate in kaolin synthetic water treatment was evaluated in terms of turbidity removal percentage and sludge volume index. Results obtained from jar testing show rotten mushroom and mushroom spent achieved turbidity removal efficiency of 99.73% and 99.25% respectively at optimal pH of 4 and optimal dosage of 5 mg/L whereas 99.91% of turbidity was eliminated by alum under optimum condition of pH 9 and dosage 25 mg/L. Under optimized condition, sludge volume index value obtained by rotten mushroom, mushroom spent and alum were 37.38 mL/g, 40.34 mL/g and 51.58 mL/g respectively. Overall, the finding indicated that mushroom waste could be a potential alternative to chemical coagulant since they are environmentally friendly, effective in turbidity removal, producing less sludge and pH independent.

Removal of Turbidity and TDS from Wastewater by Using Natural Coagulants — A Review

The highest quantity of wastewater is produced from lather industries that is mixed with oil and other pollutants and under goes to the drains from sinks, toilets, laundries, showers, etc. The wastewater is usually classified as industrial wastewater or municipal wastewater. As the population of the earth is very huge, there is a requirement that the treatment of wastewater become necessary by using different techniques. The removal of TDS and Turbidity are here done by natural coagulants such as Strychnospotatorum, Passion fruit, Phaseolus Vulgaris, Chitosan, Cicer Arietinum, Cactus, Nirmali seeds, Vingna Mungo, Ripe Okra, Surjana seed powder (SSP), Orange peel, Moringa Oleifera, and Maize seed powder. This is found from the literature review that; Jar tests were prominently used in the coagulation-flocculation process for the removal TDS and Turbidity from wastewater. The objective of this review is to find out the scope of different natural coagulants as an alternative compared to other commercial chemical-based coagulants. It has been found from the literature review that these natural coagulants are alternative, cheaper, eco-friendly, and easy to use in wastewater treatment.