Removal of suspended solids and residual oil from palm oil mill effluent

Palm oil mill effluent (POME) was pretreated to remove suspended solids and residual oil. The processes used were flocculation, solvent extraction, adsorption and membrane separation. Flocculation was used to remove suspended solids, and solvent extraction and adsorption processes were used to remove residual oil. Membrane separation was subsequently applied to remove any residual suspended solids and oil remaining after the pretreatments. The solvent extraction and adsorption processes were operated on a batch basis whereas membrane separation was performed in continuous mode. The treatment efficiency of the processes was measured as percentage removal of suspended solids and oil respectively. The optimum values of the process parameters obtained in the flocculation process were an alum dosage of 4000 mg dm^?3, mixing speed of 150 rpm for 1 h and sedimentation time of 270 min, resulting in 93% suspended solids removal. In the solvent extraction process, a 95% reduction in residual oil was obtained using n‐hexane as a solvent with 20 min of mixing at 200 rpm. The ratio of solvent to POME was 6:10 and carried out at pH 9. In the batch adsorption process, an 88% reduction in residual oil was obtained at a mixing speed of 100 rpm for 1 h, pH 9 and an adsorbent dosage of 300 g dm^?3. In membrane separation processes, GH and CE(GH) membranes gave 63% and 49% reductions in suspended solids and residual oil respectively at pH 9 and pressure of 1000 kPa. Copyright © 2003 Society of Chemical Industry     

混凝法预处理煤气化废水实验研究

采用絮凝沉降的方法,以硫酸为破乳剂,聚合氯化铝作无机絮凝剂,搭配使用有机絮凝剂聚丙烯酰胺,将煤气化废水进行预处理,显著降低了固体悬浮物含量和含油量。经加热蒸氨处理后,除油率达到85.5%,SS质量浓度降到25.9 mg/L,为生化处理提供了一个较清洁的环境。因脱酚率不高,后续生化处理需配合采用酚氨回收工艺。     

Comparison of Efficiency between Poly‐aluminium Chloride and Aluminium Sulphate Coagulants during Full‐scale Experiments in a Drinking Water Treatment Plant

Abstract

The efficiency of poly‐aluminium chloride (PACl) and of aluminium sulphate (alum), two commonly applied coagulant agents, was studied comparatively in this work, during full‐scale experiments in a drinking water treatment plant. The removal of suspended solids (turbidity) and the residual aluminium concentrations were carefully monitored and they were used for the evaluation of effectiveness for each coagulant, as well as for the determination of optimal operative conditions. Two alternative treatment processes were examined:

• (a) the conventional coagulation‐flocculation‐sedimentation process, followed by gravity filtration through sand filter beds, and

• (b) the direct filtration process, i.e., coagulation‐flocculation and sand filtration, but without the intermediate sedimentation step.

PACl proved to be a more efficient coagulant than alum, as lower dosages of PACl, about 1.35 mg Al/L in this case, resulted to the production of treated water with low turbidity and residual aluminium content. In addition, the direct filtration process through dual sand‐anthracite filter beds was found to be equally sufficient, as the conventional one, i.e., when applying the sedimentation step; in this case, 0.70 mg Al/L of PACl resulted in low turbidity water (around 0.1 NTU) and residual aluminium content (lower than 150 µg/L). In addition, the operation time of filters was extended to more than 24 hours.     

Cationic starch for microalgae and total phosphorus removal from wastewater

The city of Logan, Utah treats wastewater in 460 acres of facultative lagoons. Naturally growing algae in these lagoons uptake nutrients and remediate the wastewater, but require coagulation and flocculation for separation from wastewater. Cationic corn starch and cationic potato starch with a degree of substitution 1.34 and 0.82, respectively, were synthesized using 3‐methacryloyl amino propyl trimethyl ammonium chloride and tested on Scenedesmus obliquus and lagoon wastewater. The zeta potential of the cationic starches tested over a pH range 5.0–10.0 showed an average of +16.0 and +15.1 mV for cationic corn starch and cationic potato starch, respectively. Total suspended solids removals of 90 and 85% were achieved with cationic corn starch and cationic potato starch, respectively, when tested with S. obliquus. Tests with wastewater showed total suspended solids removals of 80 and 60% for cationic corn starch and cationic potato starch, respectively. Total phosphorus removal values from wastewater were approximately 33, 29, and 42% for cationic corn starch, cationic potato starch, and alum, respectively, for a coagulant/algae ratio of 1.4 (wt/wt). These results indicate that cationic starch has the potential to replace alum for algae harvesting and wastewater treatment making it a suitable alternative to inorganic coagulants and flocculants. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2572–2578, 2013     

In‐line Flocculation‐Submersed MF/UF Membrane Hybrid System in Tertiary Wastewater Treatment

Abstract

Coagulation/flocculation pre‐treatment of feeds can successfully mitigate the drawbacks of membrane micro‐ and ultra filtration processes: fouling and limited ability to remove organic pollutants. Laboratory experiments conducted with a synthetic wastewater (representing biologically treated secondary effluent) using 0.1 µm pore size hollow fiber membrane showed that simple in‐line flocculation pre‐treatment with inorganic coagulants dramatically reduced membrane fouling rates. The hybrid system also ensured over 70% organic matter removal in terms of dissolved organic carbon (DOC). In the experiments in in‐line flocculation outperformed clarification pre‐treatment at optimum coagulant dosages. Differences in floc characteristics and elevated suspended solids concentrations in the membrane tank may explain this finding, but the exact causes were not investigated in this study. The beneficial effects of in‐line flocculation pre‐treatment to MF/UF separation were also confirmed in the treatment of septic tank effluent in a membrane bioreactor (MBR). The fouling rate of the 0.4 µm pore size (flat‐sheet) membrane was substantially reduced with 10–100 mg L^?1 ferric chloride coagulant doses, and total dissolved chemical oxygen demand (DCOD) removal also increased from 66% up to 93%. These findings are consistent with the results of other experimental studies and show that pre‐treatment controls submersed MF/UF filtration performance.     

Pilot‐scale treatment of waste‐water from carbon production by a combined physical–chemical process

BACKGROUND: Due to its strong colour, high concentrations of fluorides and chemical oxygen demand (COD_Cr) and large amount of suspended solids (SS), the waste‐water from carbon production (WCP) seriously affects the stability of the circulating system of Guizhou Branch, Aluminium Corporation of China. In this paper, the performance of a pilot‐scale (24 m³ d^?1) combined treatment plant, consisting of chemical precipitation, coagulation, and Fenton oxidation, for the treatment of WCP was investigated. RESULTS: Lime precipitation and hydrated ferrous sulphate (HFS) coagulation, with polyacrylamide (PAM) as a coagulation aid, proved to be effective in the removal of colour (>70%), suspended solids (SS) (>90%) and fluoride (>80%) from the WCP. Subsequent Fenton oxidation combined with coagulation as a final treatment efficiently removed SS, F^?, COD_Cr, dissolved organic carbon (DOC) and colour. The average total removal efficiencies of these parameters in the pilot‐scale combined technology were as follows: SS = 98.8%, F^? = 95.7%, COD_Cr = 94.8%, DOC = 91.8% and colour = 98.3%, giving an average effluent quality: colour 24 (multiple), COD_Cr 168 mg L^?1, DOC 80 mg L^?1, F^? 38 mg L^?1 and SS 44 mg L^?1, consistent with the reusable water limits for the process. CONCLUSIONS: The current experimental results and the economic evaluation suggest that the combined process could be advantageous and feasible for the treatment of WCP. Copyright © 2009 Society of Chemical Industry     

Polyacrylamide-induced coagulation process removing suspended solids from palm oil mill effluent

Palm oil mill effluent (POME) is a colloidal suspension with 2–4% suspended solids. About 50% of the suspended solids are cellulosic compounds, which are not degraded in the typical biological treatment systems. Chemical (polymer-induced coagulation) and physical (settling) pretreatment methods were examined to remove the suspended solids in this study. A novel physicochemical treatment with high water recovery and sludge compressibility including three cationic polyacrylamides (C-PAM; as coagulant) and three anionic polyacrylamides (A-PAM; as flocculant) with different molecular weights and charge densities was used. The coagulants used were biodegradable. The combination of a C-PAM (Chemfloc1515C) with medium molecular weight and charge density and an A-PAM (Chemfloc 430A) with high molecular weight and charge density at doses of 300 and 50 mg/dm³ showed the best total suspended solids (TSS) and chemical oxygen demand (COD) removal (96.4 and 70.9%, respectively). The optimal condition was found at pH 5, rapid mixing at 150 rpm for 1 min, and slow mixing at 40 rpm for 30 s. As a conclusion, the physiochemical pretreatment using biodegradable coagulants was a promising alternative to effectively separate TSS (96.4%) with high water recovery (76%).     

Comparable evaluation of various commercially available aluminium‐based coagulants for the treatment of surface water and for the post‐treatment of urban wastewater

In this study the efficiency of various commercially‐available coagulants, ie alum and poly‐aluminium chlorides (PACls), for the treatment of surface (river) water, or for the post‐treatment of biologically pretreated urban wastewater were investigated. The different coagulants were comparatively evaluated, considering the removal of suspended solids (SS), natural organic matter (NOM), as well as the residual aluminium concentration, and the removal of phosphates (inorganic phosphorus), in the case of urban wastewater treatment. The dynamics of flocculation were also studied using a Photometric Dispersion Analyser (PDA) in order to compare the flocculation rates and the strength of different coagulant flocs. Finally, the optimum operational conditions, ie coagulant dosage, pH, temperature, duration and intensity of (initial) rapid‐mixing rate, were determined for the examined cases. It can be generally supported that PACl coagulants were superior to alum, as they presented higher SS and NOM removal, stronger and larger flocs, higher flocculation rates and lower residual aluminium concentration, which is a very important factor, especially for the treatment of surface water destinated for potable use. Copyright © 2005 Society of Chemical Industry     

Removal of turbidity from drinking water using natural coagulants

The ability of three plant materials, seeds such as Moringa oleifera, Strychnos potatorum and Phaseolus vulgaris, to act as natural coagulants was tested using synthetic turbid water formulated to resemble the drinking water. An improved and alternative method for the extraction of the active coagulant agent M. oleifera, S. potatorum, P. vulgaris seeds was developed and compared with the conventional water extraction method. In the new method the seeds were extracted using different solvents of NaCl and NaOH to extract the active coagulant agent from natural coagulants. In addition, ultrasound was investigated as a potential method to assist the extraction process. Batch coagulation experiments were conducted to evaluate the performance of the extracted coagulant achieved through various schemes. The optimum turbidity removal at different values of initial synthetic wastewater turbidity from 100 to 500 NTU was investigated. Sodium chloride at 0.5 M was found to provide a high turbidity removal of >99% compared to NaOH and distilled water extract. Among these three coagulant M. oleifera seed extracts is the highest performance in turbidity removal. The optimum coagulant dosage showed the coagulation with blended coagulant M. oleifera, S. potatorum and P. vulgaris. The study was carried out for initial turbidity of the sample such as 100 NTU (low), 250 NTU (medium) and 500 NTU (high). For the natural coagulant dosage was found to be 250–1000 mg/L respectively. It was found that the percentage of removal is highest in M. oleifera.     

Pretreatment of papermaking‐reconstituted tobacco slice wastewater by coagulation–flocculation

A study using coagulation–flocculation method for the treatment of papermaking‐reconstituted tobacco slice wastewater had been carried out. Polyaluminum chloride (PAC) and polyferric sulfate (PFS) as coagulants, and four kinds of polyacrylamides (PAMs) as flocculants, were employed during the coagulation–flocculation process. The effects of three factors, that is, the dosage of coagulants, the dosage of flocculants and pH on the treatment efficiency of the process were evaluated. The results showed that the efficiencies of PAC and PFS on the reduction of COD, ammonia nitrogen (NH₃‐N) and total suspended solids (TSS) in the treated effluents were equivalent; however, the efficiency of PAC on the color reduction was much higher than that of PFS. In the presence of PAC, a cationic polyacrylamide with very high molecular weight and low charge density (i.e., PAM4) was found to give the highest coagulation–flocculation efficiency. At the optimal conditions, that is, pH of 6.5, PAC dosage of 500 mg/L, and PAM4 dosage of 5 mg/L, the reductions of COD, NH₃‐N, color, and TSS in the process were found to be 70.8, 84.8, 72.3, and 98.5%, respectively. The study also showed that the PAC‐PAM4 scheme can remove the most of aluminum from the raw water. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1092‐1097, 2013     

Treatment of tannery wastewater by chemical coagulation

The objective of this study was to develop a treatment system that can effectively reduce the concentration of pollutants in tannery wastewater to environmentally acceptable levels and that can greatly reduce the cost of discharging the effluents. Aluminium sulphate and ferric chloride were used as a coagulant in the process. The influence of pH and coagulant dosages on the coagulation process was studied and conditions were optimised corresponding to the best removal of organic matters, suspended solids as well as chromium. The COD and chromium were removed mainly through coagulation: 38-46% removal of suspended solids, 30-37% removal of total COD from settled tannery wastewaters and 74-99% removal of chromium at an initial concentration of 12 mg/l can be achieved by using the optimum coagulant dosage (800 mg/l) in the optimum pH range (around 7.5). Ferric chloride produced better results than aluminium sulphate. The initial chromium concentrations and pH values of the wastewater had a great effect on chromium removal efficiency. Low chromium concentrations and high pH produced a more effective result on chromium removal than high chromium concentrations and low pH. Higher dosages did not significantly increase pollutant removal and were not economical. Coagulation combined with centrifugation improved the removal efficiency of suspended solids (70%). A high degree of clarification is attained as indicated by an excess of 85-86% colour removal. The results provide useful information for tannery wastewater treatment.     

Azo dye removal by Moringa oleifera seed extract coagulation

In this paper, the ability of Moringa oleifera seed extract–among other natural coagulants–to remove several different types of dyes has been researched. Moringa oleifera has been demonstrated to have a high removal ability for anionic dyes. This study is particularly focused on testing the removal of an azo dye such as Chicago Sky Blue 6B (CSB). It has taken out the fast kinetic of coagulant action and the high potential of this coagulant agent to treat wastewater from dyestuff. Up to 99% of CSB removal has been achieved with M. oleifera extract dosage of 150, 200 and 250 mg l^?1 for 100, 160 and 200 mg l^?1 of initial CSB concentration, respectively. Temperature does not affect the coagulant process and a pH level greater than 8 has a negative influence. Lower CSB percentage removal is achieved by increasing the initial dye concentration, but an optimum relationship between dye amount removed and M. oleifera extract amount has been established and it appears to be between 0.7 and 0.9, depending on the initial dye concentration and the bulk of the remaining dye concentration.     

An integrated approach for coal tailings management

A detailed study on an integrated process featuring three distinct mechanisms (i.e., hydrophobic extraction, coagulation and flocculation) is presented. In this process, fine coals in the tailings stream are extracted into a mineral oil by hydrophobic extraction, while coagulant and flocculant are used to aid effluent clarification by coagulation/flocculation. With a single stage process, a coal‐in‐oil mixture is produced as a potential fuel, while clarifying the water for recycling. The hydrophobicity of coal is found to be a key parameter in coal extraction. The addition of mineral oil prior to flocculant and coagulant, especially in the presence of fine clays, is beneficial for recovering weakly hydrophobic fine coals. Fine clays are found to stabilize coal‐rich oil droplets, reducing coal recovery. The presence of hydrophobic coal enhances droplet coalescence and improves process performance. In a case study using a tailings stream from OBED coal preparation plant, it was found that re‐grinding of original tailings is necessary to expose fresh hydrophobic surfaces. Applying this single stage unit operation to a tailings containing 52% ash, a combustible recovery greater than 85% in the form of coal‐in‐oil mixture at product ash content less than 14 wt% was achieved.     

Effects of O3, O3/H2O2 and Coagulation on Natural Organic Matter and Arsenic Removal from Typical Northern Serbia Source Water

The objectives of this study were to investigate the effects of ozone and the O₃/H₂O₂ process on FeCl₃ coagulation efficiency for the removal of the high content of natural organic matter (NOM) and arsenic (As) from groundwater (DOC = 9.27 ± 0.92 mg/L; 51.7 ± 16.4 µg As/L). Arsenic and NOM removal mechanisms during coagulation/flocculation are well investigated. However, data concerning arsenic removal in the presence of NOM, which is the subject of this article, are still insufficient. Laboratory and pilot plant test results have shown that the competition of NOM and As for adsorption sites on the coagulant surface have great influence on coagulation/flocculation efficiency for their removal. With both oxidation pre-treatments, arsenic content after the coagulation process was less than 2.0 µg/L in treated water. Application of ozone has a lower influence on coagulation efficacy in terms of DOC reduction, compared to the O₃/H₂O₂ process with the same ozone dose.     

Population Balance Model (PBM) for flocculation process: Simulation and experimental studies of palm oil mill effluent (POME) pretreatment

The present study is intended for the first time to completely replace the inorganic coagulants with organic polymers in palm oil mill effluent (POME) pretreatment by using direct flocculation of single and dual polymer systems under applied shear. The efficiency of direct flocculation of POME was investigated by using the Population Balance Model (PBM) which considered the charge neutralization and bridging attraction under applied shear. The collision efficiency was calculated based on the Derjaguin Landau Verwey Overbeek (DLVO) theory which considered the effect of adsorbed polymer layers on van der Waals attraction and bridging attraction. This is the first attempt to correlate the floc size distribution from PBM to the indirect indicators of COD, suspended solids, oil and grease. The model predictions are in close agreement with the experimental results for both single and dual polymer systems. The interaction energy curves based on PBM shows that the flocculation using cationic polymer is by charge neutralization and bridging attraction whereas flocculation using anionic polymer is by only bridging attraction. At the optimum flocculation conditions, 99.66%, 55.79%, 99.74% and 80.78% of suspended solids, COD, oil and grease removal and water recovery are achieved, respectively. The direct flocculation process significantly reduced the treatment cost by a factor of 3.6 compared to the conventional coagulation–flocculation process.     

Comparable Evaluation of Iron‐based Coagulants for the Treatment of Surface Water and of Contaminated Tap Water

Abstract

The aim of this study was to investigate the efficiency of various commercially‐available coagulants based on iron, such as ferric or ferrous salts, or polyferric sulfate (PFS), for the treatment of surface (river) water in order to become drinkable. These coagulants were evaluated, considering the removal of suspended solids (SS), of natural organic matter (NOM) and of the residual iron concentration. Furthermore, the kinetics of flocculation was studied by using a Photometric Dispersion Analyzer (PDA), comparing the different flocculation rates. The optimum operational conditions, i.e. coagulant dosage, pH value, duration, and intensity of (initial) rapid‐mixing rate, were determined for the examined cases. The results indicated that certain trivalent iron coagulants [Ferrisol‐123 (based on FeClSO₄) – Ferrisol‐Cl‐130 (based on FeCl₃)] showed higher efficiency, than the divalent [Ferrosol‐9 (based on a mixture of FeSO₄ and FeCl₂), presenting higher SS and NOM removal, higher flocculation rates, and lower residual iron concentration.     

混凝气浮-SBR-CRI组合工艺处理低浓度农药废水

采用混凝气浮-SBR-CRI组合工艺处理合肥循环经济示范园内的农药废水,结果表明:混凝气浮作为预处理措施,能够有效去除悬浮物和部分有机物;在生化池中添加大粪,提高了废水的可生化性,补充了碳源,使CODCr、BOD5、NH3-N和TP的去除率分别在80%、90%、70%、90%以上;CRI作为深度处理工艺,进一步降低废水毒性,确保系统出水达标排放。中试研究证明该组合工艺处理低浓度农药废水经济可行。     

含聚采油废水的混凝工艺研究

以PAC为凝聚剂,PAM+为絮凝剂,对原油终端处理厂含聚采油废水进行了混凝工艺研究,考察了凝聚阶段、絮凝阶段桨叶转速及搅拌时间对沉淀出水浊度的影响。结果表明:在凝聚阶段和絮凝阶段工艺条件相同,桨叶转速为300~550 r/min,搅拌时间均为30 s的条件下,沉淀出水浊度为4.5~5.5 NTU。与传统的混凝工艺相比,处理效果显著提高,且搅拌强度增强,搅拌时间大幅缩短。该项研究有利于提高原油终端处理厂进水流量,对保障海上注聚采油平台正常生产具有重要意义。     

A bioprocessing mode for simultaneous fungal biomass protein production and wastewater treatment using an external air‐lift bioreactor

A pilot plant investigation for bioprocessing has been undertaken to develop a simple, non‐aseptic, low‐cost single process for production of fungal biomass protein (FBP) and wastewater treatment using starch processing wastewater. It has been confirmed that the newly developed external air‐lift bioreactor was very suitable for bioconversion of starch materials and FBP production by the microfungi Aspergillus oryzae and Rhizopus arrhizus. Bioproduct yields of 8.5 g dm^?3 of FBP that contained 46–50% protein were obtained within a comparatively short retention time. A fungal biomass productivity in a range of 0.85–0.92 g dm^?3 h^?1 and removals of total suspended solids and 95% COD were achieved in batch, semi‐continuous and continuous processes. The operation modes of the semi‐continuous and continuous processes demonstrated a high biological dynamics in fungal biomass productivity and COD reduction. The semi‐continuous process appeared to be the most practical mode. © 2001 Society of Chemical Industry     

Acacia mearnsii de Wild Tannin-Based Flocculant in Surface Water Treatment

Abstract

Drinking water and wastewater treatment usually requires a coagulation/flocculation stage. Some disadvantages are presented by usual agents, above all linked to environmental, economical, and health aspects. Effectiveness of a new wood-derived flocculant agent has been studied, it consists of Acacia mearnsii modified tannin extract. Results have been very satisfactory; low flocculant dosage (up to 10 mg· L^{? 1}) may remove almost all suspended matter in surface water. Flocculant works better in acid pH (4–5), but an accurate dose minimizes the influence of this factor. Temperature does not affect effectiveness, but high initial turbidity may raise process efficiency. Duration of coagulation and flocculation stages seems to affect both positively to turbidity removal and in a non-interaction way. Dosage is much more important than both coagulation or flocculation stages. Treated water does not present either organic matter significantly increasing or a high residual tannin concentration. Microorganisms as total coliforms, fecal coliforms, and fecal streptococcus have been reduced up to 80%, 90%, and 99%, respectively.