Options to improve the coagulation process operation in a drinking water treatment plant. Case study

Aluminum salts are widely used across Romania in surface water treatment as coagulants. It is well-known that the efficiency of these coagulants has a complex dependency on the nature of the raw water, being affected by temperature, pH, and suspended solids. The objective of this case study was to compare the coagulation-flocculation efficiency process of raw water from the Bega River, at low temperature and turbidity, taking into account the use of alternative coagulating agents such as alum, poly aluminum chloride (PAC), and their mixing in 1:1 ratio. The raw water samples were treated using the "Jar Test" procedure, comparable with the current plant conditions at Timisoara Waterworks and taking into account possible operational improvements. For the mixture method applied in which was combined alum and PAC in 1:1 mixing ratio were achieved lower concentrations in aluminum residual, TOC, and turbidity.

The effect of chitosan concentration on flocculation efficiency microalgae Porphyridium cruentum (Rhodhophyta)

Porphyridium cruentum is a species of red microalgae belongs to the family Porphyridiophyceae, divisi Rhodophyta. P. cruentum contains a lot of nutrients which are very useful as functional food. The purpose of this research is to determine the effect of chitosan concentration on the flocculation efficiency of P. cruentum. In this study, there were two treatments, namely the concentration of chitosan and the time of flocculation with 3 replications. Chitosan used were 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 ppm. The flocculation efficiency were carried out at 10, 20, 30 and 40 minutes. The highest density was reached on the seventh day as amount 1720x104cell/mL. The results showed that there was an effect of Chitosan concentration on flocculation efficiency (Anova two way; Fcount = 4.109; df (9; 80); p=0.01). In addition, there was an effect of flocculation time on flocculation efficiency (Anova two way, Fcount = 4.498; df (3;80)). Furthermore, there was an interaction effect between the chitosan concentration and the time of flocculation. (Anova two way; Fcount = 26.635; df (2;80)). The greater the value of chitosan concentration given the greater the value of flocculation efficiency.

Evaluation of Pb, Mg, Al, Zn, and Cu as Electrode Materials in the Electrocoagulation of Microalgae

Apart from the conventionally used iron (Fe) and aluminum (Al) electrodes in microalgae harvesting, experiments were designed to examine the viability of lead (Pb), magnesium (Mg), zinc (Zn), and copper (Cu) as electrode materials in the harvesting of microalgae. The effect of voltage on the flocculation efficiency (FE) of the electrode materials was examined and compared. By dividing the optimal FE values by their corresponding periods, a simple yet practical approach was used to rank the electrode materials. From highest to lowest flocculation efficiency, the results were as follows: Cu, Zn, Mg, Al, and Pb at 10 V; Mg, Zn, Cu, Al, and Pb at 20 V; and Mg, Zn, Al, Cu, and Pb at 30 V. Important factors such as temperature, periodic FE, consumption of electrode material, pH, and metallic concentrations in the effluent were evaluated. The temperature increase proposed to have been affected by electric resistance drop and anodic corrosion, between 1.7 °C and 3.3 °C, 5 °C and 8.9 °C, and 10.5 °C and 18.4 °C was recorded at 10 V, 20 V, and 30 V respectively. Except for the supernatants of the experiments from Al electrodes, which remained relatively unaffected by voltage and time, the pH of all the other supernatants increased with time and voltage. The effluents recorded metallic concentrations between 0.513 mg/L and 43.8 mg/L for Pb, 7.02 mg/L and 20.5 mg/L for Mg, 1.34 mg/L and 9.09 mg/L for Al, 0.079 mg/L and 0.089 mg/L for Zn, and 0.252 mg/L and 0.434 mg/L for Cu electrodes.

Methylated mud snail protein as a bio-flocculant for high turbidity wastewater treatment

The authors reported a potential candidate methylated mud snail protein (MeMsp) as an effective and eco-friendly flocculant to treat the high turbidity wastewater. MeMsp was obtained by extraction of mud snail protein (Msp) through isoelectric precipitation (PSC-IP) and then methylated via the esterification with side-chain carboxyl. Structural characterization of FT-IR, Zeta potential and elemental analysis were carried out and further confirmed the successful of the methylation Flocculation experiments with kaolin suspension simulated wastewater indicated that MeMsp-24 displayed more excellent flocculation efficiency at a low dosage. At the optimum dosage 27 mg/L, the maximum clarification efficiency of MeMsp-24 was 97.46% under pH 7.0. Furthermore, MeMsp-24 exhibited a wide flocculation window in the pH range of 1.0–9.0, and faster sedimentation velocity and larger flocs size. Meanwhile, MeMsp-24 exhibited 92.12% clarification efficiency in treating railway tunnel construction effluent. The flocculation kinetic and mechanism analysis revealed that the most effective particle collision occurred at the optimal dosage, with charge neutralization and adhesion played irreplaceable roles in different environment, respectively. Therefore, through the extraction and methylation modification, the MeMsp could be a promising eco-friendly flocculant for high turbidity wastewater treatment.

Flocculation-based methods of microalgae removal from the eutrophic pond enrichment culture

The method of flocculation of biomass from the water depth to the bottom can be applied in case of local algae blooms. In our research, the combined application of FeCl3 and Polyethyleneoxide-based cationic flocculant was applied for the first time for the harvesting of the enrichment culture obtained from the reservoir during eutrophication. The effects of coagulant (FeCl3·6H2O), various flocculants based on polyacrylamide (PAA), polyethylenoxide (PEO) and flocculated biomass as ballast agent, dosage and sedimental time on flocculation efficiency of harvesting enrichment culture obtained from Pond Chernoistochinsky during eutrophication have been studied. The results show that the flocculation efficiency achieved about 90% after 5 min of sedimentation when adding of coagulant and flocculant mixture (FeCl3 30 mg/L + PEO based Sibfloc-718 2.5 mg/L) or flocculant with ballast agent (FeCl3 30 mg/L + Sibfloc-718 2.5 mg/L + 1,7% flocculated biomass). PAA, PEO and FeCl3·6H2O did not demonstrate a sufficient flocculation capacity with enrichment culture containing different types of microalgae.

Application of a modified biological flocculant in total nitrogen treatment of leather wastewater

Leather wastewater harms the ecological environment and human health. In this study, a modified bio-flocculant was prepared to facilitate treatment of leather wastewater. A bio-flocculant produced by Bacillus cereus was combined with amphoteric starch and modified using a cerium ammonium nitrate initiator. Single factor optimization and orthogonal optimization were used to determine the optimal preparation conditions as follows: amphoteric starch-to-flocculant ratio = 22:30; reaction temperature = 64 °C; initiator dosage = 2.00%; reaction time = 15 min; stirring speed = 600 rpm; and flocculation system pH = 8.0. At a dosage of 1 g/L added to simulated leather industry wastewater, the flocculation efficiency (98.17%) and the total nitrogen removal efficiency (100.00%) of modified bio-flocculant was superior to that achieved by 1 g/L of unmodified bio-flocculant (72.16% and 50.00%, respectively), amphoteric starch (8.50% and 0.00%) and polyacrylamide (95.55% and 75.00%). Analysis of natural and flocculated precipitates in the wastewater showed that the modified bio-flocculant significantly changed several characteristics of the flocculated particles; in addition, it promoted the removal of nitrogenous substances in the process of denitrification. These changes helped explain the material's flocculating ability. The results confirmed that the modified bio-flocculant was an effective additive for treating leather wastewater.