Coagulation Sedimentation Research Articles

Reduction of P2O5 and F from Phosphogypsum by CaO addition

Waste of Phosphoric acid industry, which called phosphogypsum consists of 65% gypsum, 25% water and 10% impurities. Phosphogypsum can only be used up to 15% and the rest is thrown away. The objective purpose of this study is to reduce the content of P2O5 and F using best variable CaO and stirring during coagulation process, flocculation and sedimentation. The method of this experiment is conducted by using the ratio of phosphogypsum and variable distilled water 1:1, 1:2 and 1:3, and then put it into a jar test using the variable stirring of 100 and 150 rpm. Then 11, 12 and 13 gram CaO and 50 ml distilled water is added as variables for coagulation – flocculation process. pH is kept at 6 by adding 4% NaOH. Polyalumunium chloride (PAC) 0.1% as much as 1.75 mg/l is added into the mixture and stirred at 30 rpm for 20 minutes. The separation of P2O5 and F, is done by the sedimentation process. These experimental results show that variable 1:2 (w/v), 12 gram CaO and 150 rpm stirring able to reduce fluoride and P2O5 up to 98.5% and 50% from phospogypsum.

Pepper mild mottle virus as a process indicator at drinking water treatment plants employing coagulation-sedimentation, rapid sand filtration, ozonation, and biological activated carbon treatments in Japan.

To assess the potential of pepper mild mottle virus (PMMoV) as a viral process indicator, its reduction through coagulation-sedimentation (CS) and rapid sand filtration (RSF) were compared with those of Escherichia coli, previously used viral indicators, and norovirus genotype II (NoV GII; enteric virus reference pathogen) in a bench-scale experiment. PMMoV log10 reductions in CS (1.96 ± 0.30) and RSF (0.26 ± 0.38) were similar to those of NoV GII (1.86 ± 0.61 and 0.28 ± 0.46). PMMoV, the most abundant viruses in the raw water, was also determined during CS, RSF, and advanced treatment processes at two full-scale drinking water treatment plants under strict turbidity management over a 13-month period. PMMoV was concentrated from large-volume water samples (10-614 L) and quantified by Taqman-based quantitative polymerase chain reaction. The PMMoV log10 reduction in CS (2.38 ± 0.74, n = 13 and 2.63 ± 0.76, n = 10 each for Plant A and B) and in ozonation (1.91 ± 1.18, n = 5, Plant A) greatly contributed to the overall log10 reduction. Our results suggest that PMMoV can act as a useful treatment process indicator of enteric viruses and can be used to monitor the log10 reduction of individual treatment processes at drinking water treatment plants due to its high and consistent copy numbers in source water.

Distribution of perfluorinated compounds in drinking water treatment plant and reductive degradation by UV/SO32- process.

Perfluorinated compounds (PFCs), which are widely used in industrial and residential areas, have a large negative impact on the environment. This study investigated the removal efficiency of five PFCs in a drinking water treatment plant. The results indicate that the total PFC concentration in raw water is 261.51ngL-1 and that perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are the predominant pollutants. Among all of the treatment processes, coagulation sedimentation process had the highest removal ratio of PFCs (36.12%), and removal ratio was the least in the sand filtration process. The ozonation/activated carbon and disinfection processes increased the concentration of PFCs. Therefore, developing an effective treatment to degrade PFCs is feasible. In this study, we proposed a method using UV irradiation of SO32- at 365nm to degrade PFCs. The SO32- concentration, pH, and initial concentration had profound impacts on the degradation of PFCs. When the PFC initial concentration was 20mgL-1, the SO32- concentration was 2.4gL-1, and in the presence of buffer, the degradation of PFCs was the most efficient, with the degradation ratio close to 100% after 60min of reaction. During the degradation of PFCs, short-chain PFCs and hydrofluorinated carboxylic acid were generated. From the above, we proposed a detailed mechanism of degradation and its possible pathways.

Hydrolytic Acidification of Jujube Processing Wastewater + Contact Oxidation Treatment Test

In this paper, it uses the technology of coagulation sedimentation – hydrolytic acidification – contact oxidation in treating the jujube processing wastewater, which makes membrane forming on the combined filler in reactor successfully by adopting domestic wastewater, and then dilutes jujube processing wastewater with domestic wastewater according to certain proportion to realize acclimatization of the biological membrane and complete starting of the reactor, and finally completes the biochemical treatment test of the jujube processing wastewater diluted by the feed water via backflow of the yielding water. The yielding water is stable during the test operation, and it has greater removal efficiency as to CODcr and ammonia nitrogen. Jujube is full of nutriments, has wide varieties, and possesses edible value, healthy-keeping value and medical value. Jujube processing has a long history in our country, there are numerous jujube processing enterprises, and the jujube is mainly processed to dried jujube, preserved fruit, jujube vinegar, jujube chips, jujube milk and jujube wine, etc. However, it has a greater difficulty to treat the wastewater generated in the jujube processing process, and the wastewater is one of the wastewaters with serious pollution in the food industry (Xu et al., 2014; Bi et al., 2010; Chen and Li, 2008; Wang et al., 2013). This test uses the technology of coagulation sedimentation – hydrolytic acidification – contact oxidation in treating the jujube processing wastewater, and achieves certain effects.

Evaluation of eighteen west african plants for water purification, potential use for rural water treatment

The current study evaluated the effectiveness of 18 West African plants for water purification. Water samples from 18 sites were collected in six villages in the Guiglo and Mankono regions of Cote d’Ivoire and analyzed for their potability according to WHO standards. Turbid water samples were treated by coagulation flocculation and sedimentation, with 18 plant extracts as coagulants, at concentrations of 200 mg·L–1. Moringa oleifera and chlorination were used as controls. Of the 18 water samples analyzed, three from hydraulic pumps were safe for drinking. For the 15 remaining samples (100–150 NTU), turbidity was reduced by 92% using Panda oleosa, Euadenia trifoliolata, Raphia hookeri, Napoleonaea vogelii, Piper guineense and Uapaca heudelotii. These plant-based coagulants showed similar performances as controls. R. hookeri and E. trifoliolata had reduction effects on iron and color of high colored water. These plants contained proteins, polysaccharides and tannins. Our findings show that plant-based coagulants, used in West Africa, may be applied to treat contaminated surface water to improve their quality for safe human drinking.

Control of aliphatic halogenated DBP precursors with multiple drinking water treatment processes: Formation potential and integrated toxicity

The comprehensive control efficiency for the formation potentials (FPs) of a range of regulated and unregulated halogenated disinfection by-products (DBPs) (including carbonaceous DBPs (C-DBPs), nitrogenous DBPs (N-DBPs), and iodinated DBPs (I-DBPs)) with the multiple drinking water treatment processes, including pre-ozonation, conventional treatment (coagulation–sedimentation, pre-sand filtration), ozone-biological activated carbon (O3-BAC) advanced treatment, and post-sand filtration, was investigated. The potential toxic risks of DBPs by combing their FPs and toxicity values were also evaluated. The results showed that the multiple drinking water treatment processes had superior performance in removing organic/inorganic precursors and reducing the formation of a range of halogenated DBPs. Therein, ozonation significantly removed bromide and iodide, and thus reduced the formation of brominated and iodinated DBPs. The removal of organic carbon and nitrogen precursors by the conventional treatment processes was substantially improved by O3-BAC advanced treatment, and thus prevented the formation of chlorinated C-DBPs and N-DBPs. However, BAC filtration leads to the increased formation of brominated C-DBPs and N-DBPs due to the increase of bromide/DOC and bromide/DON. After the whole multiple treatment processes, the rank order for integrated toxic risk values caused by these halogenated DBPs was haloacetonitriles (HANs)≫haloacetamides (HAMs)>haloacetic acids (HAAs)>trihalomethanes (THMs)>halonitromethanes (HNMs)≫I-DBPs (I-HAMs and I-THMs). I-DBPs failed to cause high integrated toxic risk because of their very low FPs. The significant higher integrated toxic risk value caused by HANs than other halogenated DBPs cannot be ignored.

Molecular characterization of effluent organic matter in secondary effluent and reclaimed water: Comparison to natural organic matter in source water

Municipal wastewater reclamation is becoming of increasing importance in the world to solve the problem of water scarcity. A better understanding of the molecular composition of effluent organic matter (EfOM) in the treated effluents of municipal wastewater treatment plants (WWTPs) is crucial for ensuring the safety of water reuse. In this study, the molecular composition of EfOM in the secondary effluent of a WWTP in Beijing and the reclaimed water further treated with a coagulation–sedimentation–ozonation process were characterized using a non-target Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) method and compared to that of natural organic matter (NOM) in the local source water from a reservoir. It was found that the molecular composition of EfOM in the secondary effluent and reclaimed water was dominated by CHOS formulas, while NOM in the source water was dominated by CHO formulas. The CHO formulas of the three samples had similar origins. Anthropogenic surfactants were responsible for the CHOS formulas in EfOM of the secondary effluent and were not well removed by the coagulation-sedimentation-ozonation treatment process adopted.

Boron removal from wastewater via coagulation sedimentation with ettringite: an experimental and mechanism study

Boron removal from wastewater via coagulation sedimentation with ettringite: an experimental and mechanism study

选矿废水净化与回用技术现状与展望

选矿废水排放量大，约占全国工业废水总排放量的十分之一；且其含有大量固体悬浮物、重金属离子与各种残留的选矿药剂，成分复杂，使得无论是选择直接外排或是回用都会造成不小的危害。本文在简要介绍选矿废水来源、特点以及危害的基础上，综合介绍了近年来广泛应用在选矿废水处理上的自然净化、酸碱中和、混凝沉降、和化学氧化等传统处理方法，以及人工湿地、微生物吸附法等选矿废水的处理新探索。通过对各种处理方法的横向对比，分析各方案的优势与不足，为选矿工作者提供解决实际选矿废水问题的思路，最后对选矿废水技术与研究方向提出展望。 The waste water produced in minerals processing has a large quantity of emission, which accounts for about 10% of the total emissions of industrial waste water. In addition, due to the excessive suspended solids, heavy metal ions and residual reagents, the waste water can cause a lot of harm whether direct discharged or reused. In this paper, based on the source, characteristics and harm of the waste water in minerals processing, the traditional methods such as natural purification, acid and alkali neutralization, coagulation sedimentation, and chemical oxidation are comprehensively introduced, and the new methods of artificial wetland and microbial adsorption are explored. At last, the advantages and disadvantages of every method are analyzed, and the technology and research direction of waste water in minerals processing are prospected.

Optimisation of contaminant removal in wet-weather sewage flows

A coagulation–sedimentation process with polyaluminium chloride (PAC) as a coagulant was used to treat wet-weather sewage flows with high concentrations of contaminants during the initial stages of a rainfall event. Response surface methodology and central composite design were applied to evaluate the optimal operating conditions of pH, turbidity and PAC dose to maximise simultaneous removal of contaminants at wastewater treatment plants. The optimal conditions were found to be a pH of 5, turbidity of 400 NTU and PAC dose of 48 mg/l. This resulted in the removal of 80·5% phosphorus, 79·8% chemical oxygen demand (COD) and 81·8% Escherichia coli. Under the assumption of wastewater with a neutral pH of 7, the optimal turbidity and PAC dose conditions resulted in the removal of 81·0% phosphorus, 76·7% COD and 64·5% E. coli.

Comparison of different advanced treatment processes in removing endocrine disruption effects from municipal wastewater secondary effluent

In this study, secondary effluent from the Wulongkou (WLK) municipal wastewater plant (Zhengzhou, China) was tested for its toxicity effects before and after five advanced treatment processes (ATPs, i.e. coagulation sedimentation, nan da magnetic polyacrylic anion exchange resin (NDMP) resin adsorption, activated carbon adsorption, ozonation and electro-adsorption). Results showed that estrogen disruption effects (EDEs) were particularly significant for the raw secondary effluent among the studied dioxin-like toxicity effect, androgenic/anti-androgenic response effect, EDEs, and genotoxicity effect. And E1, E2, and EE2 were the main endocrine disruption chemicals (EDCs) contributing to EDEs. Except coagulation sedimentation, all the other four ATPs were efficient in removing the steroid estrogens (i.e. E1, E2, and EE2), but were inefficient in the artificial EDC (i.e. DBP, OP and BPA) removal. In the ATPs treated samples, vitellogenin (VTG) in zebrafish were largely removed. However, they were still significant in comparison with the control, probably due to artificial EDCs. Therefore, finding ways to thoroughly remove EDEs and EDCs from the secondary effluent will be a new research direction in the future.

Reagents Activity in a Copper Droplets / Post-Processing Slag Suspension

Abstract The suspension of the copper droplets in the post-processing slag taken directly from the KGHM-Polska Miedź S.A. Factory (from the direct-to-blister technology as performed in the flash furnace) was subjected to the special treatment with the use of the one of the typical industrial reagent and with the complex reagent newly patented by the authors. This treatment was performed in the BOLMET S.A. Company in the semi-industrial conditions. The result of the CaCO3, and Na2CO3 chemicals influence on the coagulation and subsequent sedimentation of copper droplets on the crucible bottom were subjected to comparison with the sedimentation forced by the mentioned complex reagent. The industrial chemicals promoted the agglomeration of copper droplets but the coagulation was arrested / blocked by the formation of the lead envelope. Therefore, buoyancy force forced the motion of the partially coagulated copper droplets towards the liquid slag surface rather than sedimentation on the crucible bottom. On the other hand, the complex reagent was able to influence the mechanical equilibrium between copper droplets and some particles of the liquid slag as well as improve the slag viscosity. Finally, the copper droplets coagulated successfully and generally, were subjected to a settlement on the crucible bottom as desired / requested.

Evaluation of virus removal efficiency of coagulation-sedimentation and rapid sand filtration processes in a drinking water treatment plant in Bangkok, Thailand

In order to properly assess and manage the risk of infection by enteric viruses in tap water, virus removal efficiency should be evaluated quantitatively for individual processes in actual drinking water treatment plants (DWTPs); however, there have been only a few studies due to technical difficulties in quantifying low virus concentration in water samples. In this study, the removal efficiency of indigenous viruses was evaluated for coagulation-sedimentation (CS) and rapid sand filtration (RSF) processes in a DWTP in Bangkok, Thailand by measuring the concentration of viruses before and after treatment processes using real-time polymerase chain reaction (qPCR). Water samples were collected and concentrated from raw source water, after CS, and after RSF, and inhibitory substances in water samples were reduced by use of a hydrophobic resin (DAX-8). Pepper mild mottle virus (PMMoV) and JC polyomavirus (JC PyV) were found to be highly prevalent in raw waters, with concentrations of 102.88 ± 0.35 and 103.06 ± 0.42 copies/L (geometric mean ± S.D.), respectively. Step-wise removal efficiencies were calculated for individual processes, with some variation observed between wet and dry seasons. During the wet season, PMMoV was removed less by CS and more by RSF on average (0.40 log10 vs 1.26 log10, respectively), while the reverse was true for JC PyV (1.91 log10 vs 0.49 log10, respectively). Both viruses were removed similarly during the dry season, with CS removing the most virus (PMMoV, 1.61 log10 and 0.78 log10; JC PyV, 1.70 log10, and 0.59 log10; CS and RSF, respectively). These differences between seasons were potentially due to variations in raw water quality and the characteristics of the viruses themselves. These results suggest that PMMoV and JC PyV, which are more prevalent in environmental waters than the other enteric viruses evaluated in this study, could be useful in determining viral fate for the risk management of viruses in water treatment processes in actual full-scale DWTPs.

Advanced treatment of pharmaceutical wastewater with combined micro-electrolysis, Fenton oxidation, and coagulation sedimentation method

Due to the inability of biochemical processes to remove refractory organic compounds from wastewater in pharmaceutical industrial parks, this research tried to find a new way to meet the requirement of the Discharge Standard in China. A combined process involving micro-electrolysis, Fenton oxidation, and coagulation was studied. Considering the removal efficiencies and operation costs, the reaction conditions were optimized. The COD concentration in the effluent after the combined treatment was less than the standard limit of 50 mg/L. Molecular weight distribution of organic compounds in wastewater was analyzed by sequential filtration and ultrafiltration. When treated by the combined process, the particulate fraction (particle size > 1,000 nm) decreased, and the soluble portion (particle size < 1 nm) increased significantly. Composition of the refractory organics was investigated using GC–MS. A total of 34 types of low-molecular-weight organics were identified in the effluent, among which phthalates, amides, heterocyclic compounds, and PAHs were the main organic pollutants. All these results show that the proposed method is promising for refractory wastewater because it is efficient and easy to operate.

Tertiary Treatment Process of Preserved Wastewater

The effects of the composite coagulants on coagulation sedimentation for the preserved wastewater was investigated by changing the composite coagulant dosages, and the coagulant was composed of polymeric ferric sulfate (PFS), polyaluminium chloride (PAC), and polyaluminum ferric silicate (PAFSC), while the effect of the tertiary treatment process on the preserved wastewater was tested, which was exceeded the standard seriously. The results showed that 400 mg/L was the optimum composite coagulant dosage. The removal rates of salt and sugar were as high as 99.1% and 99.5% respectively, and the removal rates of COD Cr and SS were 99.3% and 96.0%, respectively after the preserved wastewater was treated by the tertiary treatment technology, which both reached the primary standard of “The Integrated Wastewater Discharge Standard” (GB8978-1996).

Multiple views of biological stability and optimized coagulation in the control of biostability in traditional water treatment processes: a pilot test

This study investigated biological stability in a pilot test of traditional water treatment processes in eastern China. The variations of assimilable organic carbon, biodegradable dissolved organic carbon, bacterial regrowth potential, and total phosphorus were analyzed, and the relationships among them were studied. High-purity aluminum sulfate was added as a coagulant, and the corresponding removal efficiencies of the coagulation–sedimentation unit and the sand filtration unit were evaluated. The experimental results indicate that the removal efficiencies of the dissolved organic carbon (DOC) and UV254 both increased as the alum dosages increased in the coagulation and sedimentation process. The removal efficiencies of the biostability indicators of the coagulation and sedimentation process were higher than those of the filtration treatment. The bacterial regrowth potential was correlated with DOC concentration, and the introduction of total dissolved phosphorus into the evaluation of biostability is recommended to help confirm the C:P ratio and to select the appropriate strategy for controlling bacterial regrowth. An explanation for the changes in biostability indicators is provided.

Performance of an Integrated Treatment System for Clean Drinking Water Production

This study is related to the removal of organics and other pollutants from drinking water using an integrated treatment system consisting of coagulation–sedimentation, ozonation and granular activated carbon (GAC)‐enhanced sand filtration. Standard methods and instruments were employed to measure turbidity, chemical oxygen demand determined by using the permanganate method as permanganate index (CODMn), UV254, total organic carbon (TOC), ammonia and nitrite of raw and treated water under controlled laboratorial conditions. The experimental results demonstrated that the total removal rates of turbidity, CODMn, UV254 and TOC were in the range of 98–99.9, 21–71, 33–73 and 20–47%, respectively, in different units of the integrated treatment system. GAC‐enhanced sand filtration significantly removed ammonia and nitrite, and the average removal efficiency was attained to 88 and 98%, respectively. In addition, most of the organic matter concentrations were observed to be reduced in GAC‐enhanced sand filtration and only small molecular weight compounds were detected in the effluent. All these pollutant reductions were noticed in the upper 350 mm of the activated carbon column in GAC‐enhanced sand filtration. The findings from this study suggest that the integrated treatment process can efficiently remove organics and other toxic pollutants from drinking water and can be a better alternative to conventional treatment.

Effect of cell integrity on algal destabilization by oxidation-assisted coagulation

A hybrid oxidation–coagulation process is commonly adopted to destabilize algae and subsequently improve the removal of algae from water through sedimentation and filtration in water treatment plants (WTPs). Preoxidation is crucial to improving algae removal by a coagulation–sedimentation process. The goal of this study was to investigate the effect of oxidation with NaOCl and ClO2 on the cell integrity of algae (i.e. diatoms) and the destabilization of algae by means of Alum coagulation. The effects of oxidation-assisted coagulation on the performance of sedimentation as well as filtration were evaluated. The results show that ClO2 reduces cell integrity more severely than NaOCl during oxidation. The degradation of chlorophyll a and humic-like substances generated by cells ruptured by ClO2 oxidation is stronger than that by NaOCl oxidation. During oxidation both NaOCl and ClO2 fail to cause significant cell lysis, while cell settleability can be improved markedly by using only ClO2. Preoxidation with ClO2 is more effective in destabilizing the particles and algae when applying Alum coagulation at low dosages. It was found that the residual algae counts in the supernatants are inversely well-correlated to its filterability instead of its residual turbidity. The reduced cell integrity resulting from ClO2 preoxidation effectively improves the performance of coagulation–sedimentation for algae (diatoms) removal and reduces the burden of filtration operation in the WTPs.

CaCO3 scaling of oilfield produced water in “electrochemical pre-oxidation–coagulation sedimentation–filtration” process: reason, mechanism, and countermeasure

Chemical stability of oilfield injection water is a critical factor to avoid corrosion and scaling of water treatment devices and pipelines. Especially, Guangli oilfield (a branch of Shengli Oilfield) has achieved remarkable success in anti-corrosion by applying an electrochemical pre-oxidation process into strong corrosive wastewater treatment, while scaling was aggravated therefore. XRD, SEM, EDS, and chemical analysis demonstrated the major component of the scale deposit was calcite. Succeedingly, chemical analysis of produced water along the process showed that pH, concentration of calcium ions, bicarbonate ions, and suspended solids changed remarkably before and after the mixing reactor. Further studies revealed that the addition of water treatment chemicals (Na2CO3) in the mixing reactors induced the precipitates of CaCO3, which could serve as crystal seeds and resulted in the continuous precipitation of calcium ions. Moreover, calcite saturation ratio increased from 0.97 to 3.94 could contribute to the rise of pH and bicarbonate ions. Consequently, both of them created favorable conditions for crystal growth and incurred more severe scaling problem. The final scale inhibition experiments suggested that the amount of calcium carbonate scale could be mitigated through the dose of scale inhibitors.

The enhanced removal of carbonaceous and nitrogenous disinfection by-product precursors using integrated permanganate oxidation and powdered activated carbon adsorption pretreatment

Pilot-scale tests were performed to reduce the formation of a range of carbonaceous and nitrogenous disinfection by-products (C-, N-DBPs), by removing or transforming their precursors, with an integrated permanganate oxidation and powdered activated carbon adsorption (PM–PAC) treatment process before conventional water treatment processes (coagulation–sedimentation–filtration, abbreviated as CPs). Compared with the CPs, PM–PAC significantly enhanced the removal of DOC, DON, NH3+–N, and algae from 52.9%, 31.6%, 71.3%, and 83.6% to 69.5%, 61.3%, 92.5%, and 97.5%, respectively. PM pre-oxidation alone and PAC pre-adsorption alone did not substantially reduce the formation of dichloroacetonitrile, trichloroacetonitrile, N-nitrosodimethylamine and dichloroacetamide. However, the PM–PAC integrated process significantly reduced the formation of both C-DBPs and N-DBPs by 60–90% for six C-DBPs and 64–93% for six N-DBPs, because PM oxidation chemically altered the molecular structures of nitrogenous organic compounds and increased the adsorption capacity of the DBP precursors, thus highlighting a synergistic effect of PM and PAC. PM–PAC integrated process is a promising drinking water technology for the reduction of a broad spectrum of C-DBPs and N-DBPs.