Construction and Application of Flocculation and Destability System of Biodrill-A Drilling Fluid in Bohai Oilfield

To protect the marine ecological environment of Bohai Bay, the waste drilling fluid in Bohai oilfield have to be treated. In the light of the composition characteristics of Biodrill-A drilling fluid, the compounding method of the inorganic–organic flocculants was adopted to assist the flocculation and solid–fluid separation of Biodrill-A drilling fluid. Through the orthogonal test design, the main factors impacting the flocculation effect on Biodrill-A drilling fluid were found to the concentration of inorganic flocculant CaCl2 and the flocculation pH value. The optimal flocculation treatment was further obtained through single-factor optimization. Specifically, when the inorganic flocculant CaCl2 concentration was 0.9 w/v%, the organic flocculant concentration was 0.01 w/v%, the flocculation pH was 8, and the flocculation time was 7 min. Eventually, the final dewatering rate could reach 84.02%. In the optimized compound flocculants, the inorganic flocculant CaCl2 reduced the zeta potential of clay particles by electric neutralization to decrease the repulsion among particles, and the organic one could absorb and wrap the clay particles through bridging curling and electric neutralization after flocculation destabilization. Both inorganic and organic flocculants facilitated the large flocs and particles of clay particles. The field test showed that the inorganic–organic flocculants were suitable for the on-line flocculation treatment process based on centrifugal machine. The waste drilling fluid was reduced by 82%, and the water content of the separated solid phase was as low as 25.7%.

Lime/Sodium Carbonate Treated Seawater to Improve Flocculation and Sedimentation of Clay-Based Tailings

Seawater treated with lime and sodium carbonate in different proportions to reduce magnesium and calcium contents is used in flocculation and sedimentation tests of artificial quartz and kaolin tailings. Solid complexes were separated from water by vacuum filtration, and factors such as lime/sodium carbonate ratio, kaolin content, flocculation time, and flocculant dose are evaluated. The growth of the aggregates was captured in situ by a focused beam reflectance measurement (FBRM) probe. Solid magnesium and calcium complexes are formed in raw seawater at pH 11, impairing the performance of flocculant polymers based on polyacrylamides. The results show that the settling rate improved when the treatment’s lime/sodium carbonate ratio increased. That is, when a greater removal of magnesium is prioritized over calcium. The amount of magnesium required to be removed depends on the mineralogy of the system: more clay will require more significant removal of magnesium. These results respond to the structural changes of the flocs, achieving that the more magnesium is removed, the greater the size and density of the aggregates. In contrast, calcium removal does not significantly influence flocculant performance. The study suggests the necessary conditions for each type of tailing to maximize water recovery, contributing to the effective closure of the water cycle in processes that use seawater with magnesium control.

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.

Efficacy of Chitosan as a Coagulant Aid to Alum Precipitation of Congo Red In Wastewater

The use of chitosan prepared from prawn shells as coagulant aid for congo red (CR) dye removal from wastewater was investigated in this study. Characterisation of the prepared chitosan samples showed characteristics similar to commercially available ones. The coagulation – flocculation experiment was carried out using the jar test procedure. Both chitosan and alum were used separately for the dye precipitation and then combined together. The usage of alum alone showed no precipitating effect on the CR dye molecule, while chitosan was able to considerably reduce the concentration of the dye in solution. When chitosan was used as a coagulant aid in the alum precipitation, the amount (%) of dye removed increased greatly. Optimization of the process via study of effect of pH and flocculation time at optimum alum – chitosan combination indicated that pH 4-5 and settling time of 40 min were suitable conditions for maximum decolourisation of CR dye wastewater with about 98% efficiency. Moreover, study of settling characteristics of the sludge produced from the alum-chitosan synergy was better than that produced from either of them alone. Also, occurrence of redispersion and restabilization of the precipitate was not encountered.

Critical flocculation concentration for polyvalent ions using silica nanoparticles; a new version of Schulze-Hardy rule

Critical Flocculation Concentration (CFC) is an important quantity because allows to know the optimal amount of flocculant required to remove (adsorb) specific quantities of metal ions in aqueous solution allowing to reduce both, the flocculation time and the excess of unreacted flocculant; this unreacted material produces, by itself, an additional contamination. The results reported here show that the standard Schulze-Hardy-Rule (SHR), based only in the valence z, is not longer valid to obtain the right values of CFC. In this work it is reported a correct determination of CFC for di- and tri-valent ions using different types of silica nanoparticles. Both, the initial pH slope (-pHo) and the valence z are required to determine correctly the CFC. The proposed modified version for CFC is CFC ∝ [(-pHo)z]−1.

A Novel Bioflocculant from Raoultella planticola Enhances Removal of Copper Ions from Water

Copper is one of the most toxic heavy metals. In this work, a sampling survey of copper ions in the water of Songhua River flowing through the chemical and living areas of Jilin City was studied. A new bioflocculant from Raoultella planticola was obtained. The investigation of Songhua River flowing through Jilin City shows that the copper concentration is between 0.07 ppb and 0.16 ppb. The bioflocculant supporting graphite oxide (GO) as a bioflocculant inducer used in this study has been utilized in treatment of copper ions in water. GO and bioflocculant infrared radiation (IR) spectrum and zeta potential were studied. Flocculational conditions of copper ion (0.2 ppm) were modeled and optimized using RSM (response surface methodology). Our data showed that flocculation efficiency was over 80%. Significant influencing factors and variables were pH, flocculation time, bioflocculant dosage, and GO inducer which had major impact effects on flocculation efficiency. The highest flocculation efficiency which is 86.01% was achieved at pH=5, at 1.62 h and 13.11 mg bioflocculant with 13.11 mg GO as an inducer. However, temperature (A) and GO inducer were significant impact factors on the flocculation efficiency.

Mathematical modelling and analysis of the flocculation process in low retention time hydraulic flocculators

This article aims to advance the understanding of particle interactions in low retention time flocculators and proposes a new flocculation model that appropriately considers the influence of retention time in flocculation processes. This consideration is important for units with flocculation time lower than 1 min, as seen in helically coiled tube flocculators (HCTFs), whose retention time is significantly lower than conventional flocculation units (about 30 min). With this, it was possible to obtain a more adherent model, reducing deviations between results obtained by physical modelling (using HCTFs, 48 tests) and those obtained with the proposed model, when compared with results obtained using the flocculation models commonly used for this purpose. The decreasing-rising behaviour presented by experimental data for process efficiency versus retention time, not verified in the benchmark models, was satisfactorily addressed by the proposed model. Furthermore, maximum and average absolute percentage deviations obtained using the model proposed in this study were less than or equal to the results obtained with the benchmark models and less for experimental uncertainty (10%). The results obtained indicate that this model can be a useful tool to support the rational design of low retention time units, including applications for the water industry and water recycling systems.

A Simple Explicit Expression for the Flocculation Dynamics Modeling of Cohesive Sediment Based on Entropy Considerations

The flocculation of cohesive sediment plays an important role in affecting morphological changes to coastal areas, to dredging operations in navigational canals, to sediment siltation in reservoirs and lakes, and to the variation of water quality in estuarine waters. Many studies have been conducted recently to formulate a turbulence-induced flocculation model (described by a characteristic floc size with respect to flocculation time) of cohesive sediment by virtue of theoretical analysis, numerical modeling, and/or experimental observation. However, a probability study to formulate the flocculation model is still lacking in the literature. The present study, therefore, aims to derive an explicit expression for the flocculation of cohesive sediment in a turbulent fluid environment based on two common entropy theories: Shannon entropy and Tsallis entropy. This study derives an explicit expression for the characteristic floc size, assumed to be a random variable, as a function of flocculation time by maximizing the entropy function subject to the constraint equation using a hypothesis regarding the cumulative distribution function of floc size. It was found that both the Shannon entropy and the Tsallis entropy theories lead to the same expression. Furthermore, the derived expression was tested with experimental data from the literature and the results were compared with those of existing deterministic models, showing that it has good agreement with the experimental data and that it has a better prediction accuracy for the logarithmic growth pattern of data in comparison to the other models, whereas, for the sigmoid growth pattern of experimental data, the model of Keyvani and Strom or Son and Hsu model could be the better choice for floc size prediction. Finally, the maximum capacity of floc size growth, a key parameter incorporated into this expression, was found to exhibit an empirical power relationship with the flow shear rate.

Removal of residual carcinogenic dyes from industrial wastewater using flocculation technique

Due to inefficient dyeing procedures in a typical dye industry, a large quantity of dye spills out into the wastewater, polluting it and causing serious harm to the environment. Consequently, special attention was focused on the use of a novel combination of a coagulant and a flocculant. As potato starch has already proved its strength as a bioflocculant, a combination of potato starch with iron(III) chloride as a coagulant was tested in order to achieve favorable results of dye reduction in simulated wastewater. The effect of various parameters on dye removal was investigated, like dosage of flocculant, temperature of treatment and flocculation time. Batch experimentation mode was adopted for the flocculation process, using a jar test apparatus. A mixed level parametric design (L16) was employed for experimentation. The orthogonal tests revealed that the best operating parameters were: 2% of potato starch, 60?C and 20 min of flocculation time. Furthermore, the significant factor test was performed using Minitab-17 from where the dosage of potato starch was proven to be the most significant factor. The study successfully raised dye removal efficiency up to 85% using a novel coagulant-flocculant combination. Finally, the results were compared with existing literature.

Changes in the two-dimensional and perimeter-based fractal dimensions of kaolinite flocs during flocculation: a simple experimental study

In this study, Couette flow experiments were performed to estimate the temporal evolution of the 2D and perimeter-based fractal dimension values of kaolinite flocs during flocculation. The fractal dimensions were calculated based on the projected surface area, perimeter length and length of the longest axis of the flocs as determined by sampling observation and an image-processing system. The 2D fractal dimension, which relates the longest axis length and projected surface area of flocs, was found to decrease with the flocculation time, corresponding to the production of some porous flocs from the flow shear. This fractal dimension finally reached a steady state, which resulted from a dynamic equilibrium among the floc growth, floc breakage and floc restructuring. The perimeter-based fractal dimension, which characterizes the relationship between the projected surface area and the perimeter of flocs, increases with flocculation time because the flow shear increases the collisions among the primary particles, and some irregular flocs are formed. The perimeter-based fractal dimension reaches a steady level because of the balance among floc aggregation, breakage and restructuring. In addition, a stronger turbulent flow shear makes the steady state of fractal dimensions occur early during flocculation.