Improvement of domestic wastewater primary sedimentation through ozonation

The use of ozone as an aid for flocculation‐coagulation of domestic wastewaters has been studied. Jar tests of ozonated and non‐ozonated wastewater at different coagulant (hydrated aluminum and ferrous sulfate salts) and flocculant (calcium hydroxide and A‐201 polyelectrolyte) doses have been conducted to obtain optimum floc size. Settling experiments have then been carried out to follow changes of total COD conversion and surface area of a primary settling tank needed to reach a given percentage particle separation. The results show that the use of preozonation provides beneficial results to both improve COD conversion and reduce the sedimentation surface area.     

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     

碳酸钾作为煤泥沉降凝聚剂的试验研究

基于电荷中和理论和吸附理论,传统的凝聚剂多为高价盐,低价盐作为凝聚剂的试验研究很少,本文在大量试验的基础上,对碳酸钾作为煤泥沉降的凝聚剂做了研究.试验得出碳酸钾除具有凝聚作用外,本身也具有一定的絮凝作用,当与聚丙烯酰胺搭配时,与硫酸铝相比,碳酸钾的效果更好,沉降速度更快,用量更小,上清液浊度更小.     

强化预处理乙醇废水协同除磷试验研究

酿造行业废水具有高有机物浓度、高浊、高磷等特点,对后续生物处理的十分不利。采用混凝沉淀强化处理,能够有效提高化学需氧量（COD）、悬浮物（SS）的去除率,同时降低磷浓度,对后续生物处理具有促进作用。探讨了不同混凝剂、混凝剂的投加量对混凝沉降速度和COD、浊度、磷去除效果的影响。研究表明,三氯化铁为预处理乙醇废水最佳混凝剂,在p H值为7-8时,投加量为80mg/L,沉降速度较快,COD的去除率可达59%,磷的去除率〉90%。继续投加助凝剂聚丙烯酰胺（PAM）可以提高废水的处理效果,但是不显著。     

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.     

Removal of chemical oxygen demand from textile wastewater using a natural coagulant

A biomaterial was successfully synthesized from Plantago ovata by using an FeCl₃-induced crude extract (FCE). The potential of FCE to act as a natural coagulant was tested for the pretreatment of real textile wastewater. Tests were performed to evaluate the effects of FCE quantity, salt concentration, and wastewater pH on chemical oxygen demand (COD) reduction during a coagulation/flocculation process. Experimental results indicated that the wastewater could be effectively treated by using a coagulation/flocculation process, where the BOD₅/COD ratio of the effluent was improved to 0.48. A low coagulant dose, 1.5mg/L, achieved a high COD removal percentage, 89%, at operational conditions of neutral pH and room temperature. The experimental data revealed that the maximum COD removal occurred at water pH<8. Increasing the salt promoted the COD removal. The settling and filterability characteristics of the sludge were also studied. Scanning electron microscopy and energy dispersive spectroscopy studies were conducted to determine the sludge structure and composition, respectively. Overall, FCE as an eco-friendly biomaterial was revealed to be a very efficient coagulant and a promising option for the removal of COD from wastewaters.     

Optimization of flocculation conditions for the separation of TiO2 particles in coagulation-photocatalysis hybrid water treatment

TiO₂ mediated photocatalysis can decompose organic micropollutants (e.g., 1,4-dioxane) in water, but the removal of used TiO₂ particles is challenging. Although retrofitting enhances the particle separation efficiency, optimizing a coagulation/flocculation process should be most suitable for existing treatment plants. Therefore, the present study investigated the separation characteristics of TiO₂ particles added to drinking water treatment processes along with a polyaluminum coagulant. TiO₂ photocatalysts were able to achieve significant degradation of 1,4-dioxane (∼100% within 50 min) as well as dissolved organic matter (∼75% within 150 min) at a TiO₂ dose of 1.0 g/L under UV irradiation. Although the TiO₂ particle separation efficiency was sensitive to G values, maximal removal occurred at a G value of <34 s⁻¹ with a coagulant concentration of >8 mg/L as Al₂O₃. Sand filters had the capability to remove residual turbid materials and thus, the turbidity of the final product water dropped to as low as 0.1 NTU when the coagulation/flocculation process was preceded. The final effluent quality was comparable to that of a 0.45-μm membrane filter. The post separation of the TiO₂ photocatalysts dispersed for emergency water treatment to degrade 1,4-dixoane was successfully achieved with an optimal coagulant dose, proper flocculation, and sand filtration.     

东莞运河采用一级强化处理工艺参数的确定

东莞运河河水的处理采用一级强化混凝处理工艺.在设计和运行上,由于对化学混凝沉淀工艺未能深入的理解和掌握而造成了很大的失误;针对这一存在的问题,利用烧杯试验的原理,具体介绍了化学混凝沉淀工艺的最佳速度梯度值、反应时间、聚合碱式氯化铝铁的投药量以及最佳沉淀时间.     

A Review of the Use of Chitosan for the Removal of Particulate and Dissolved Contaminants

Abstract

Chitosan has unique properties among biopolymers, especially due to the presence of primary amino groups. Chitosan has been used for the chelation of metal ions in near‐neutral solution, the complexation of anions in acidic solution (cationic properties due to amine protonation), the coagulation of negatively charged contaminants under acidic conditions, and for precipitative flocculation at pH above the pKa of chitosan. The coagulation and flocculation properties can be used to treat particulate suspensions (organic or inorganic) and also to treat dissolved organic materials (including dyes and humic acid). This paper will give an overview of the principal results obtained in the treatment of various suspensions and solutions: (a) bentonite suspensions; (b) organic suspensions; (c) anionic dye solutions; and (d) humic acid solutions. Stoichiometry and charge restabilization were determined for the coagulation of humic acid, kaolin, and organic dyes with chitosan, indicating charge neutralization as the dominant mechanism for removal. Charge patch destabilization and bridging mechanisms were inferred in other cases, based on the effects of the apparent molecular weight of the chitosan preparations and effectiveness of sub‐stoichiometric doses of chitosan. For dye solutions, results showed that color can be removed either by sorption onto solid‐state chitosan or by coagulation‐flocculation using dissolved‐state chitosan; the reactivity of amine groups was significantly increased when dissolved chitosan was used. For humic materials, chitosan can be used as a primary coagulant or as a flocculant after coagulation with alum or other inexpensive coagulants. The influence of the degree of deacetylation and the molecular weight of chitosan on its performance as coagulant/flocculant is illustrated by several examples.     

谈混凝沉淀烧杯试验标准的编制

影响水的混凝效果因素众多，如：浊度、色度、碱度和pH等，难以直接确定合适的混凝剂及加注量，而混凝沉淀试验是对水的混凝沉淀研究及指导生产的最有效方法。文章介绍混凝沉淀试验标准编制宗旨、主要内容及有关问题的说明。     

常规絮凝工艺与加载絮凝工艺处理锌、铜废水的研究

以含锌废水和含铜废水为研究对象,在常规絮凝工艺和加载絮凝工艺中,对其处理含锌废水和含铜废水时pH的影响、混凝剂投加量的影响、以及助凝剂投加量的影响进行对比研究。结果表明,在其各自的最佳工况下,加载絮凝工艺比常规絮凝工艺对pH变化适应性更强,投药量更少,重金属去除效果更好,出水总锌、总铜、浊度分别稳定在1 mg/L、0.1 mg/L、0.5 NTU以下,远低于《广东省水污染物排放限制标准》（DB4426-2001）一级排放标准。     

含镍废水处理中的助凝助沉工艺研究

将粉煤灰等几种物质应用于含镍废水处理中作为助凝助沉剂。试验研究了各自的最优加入量,对比了彼此的助凝助沉效果,结果表明,对试验的含镍废水,首选助凝助沉剂为粉煤灰,在100mL含镍废水中加入0.3g粉煤灰,可加速沉降,沉降在5min内基本完成,污泥的体积由原来的33.6%减少到14.1%,滤饼的含水量由88.27%降低到81.48%,并进行了工业试验。     

Palm oil mill effluent pretreatment using Moringa oleifera seeds as an environmentally friendly coagulant: laboratory and pilot plant studies

This research paper covers the suitability of the coagulation–flocculation process using Moringa oleifera seeds after oil extraction as a natural and environmentally friendly coagulant for palm oil mill effluent treatment. The performance of M. oleifera coagulant was studied along with the flocculant KP 9650 in removal of suspended solids, organic components and in increasing the floc size. The optimum values of the operating parameters obtained from the laboratory jar test were applied in a pilot‐scale treatment plant comprised of coagulation–flocculation and filtration processes. Pilot‐scale pretreatment resulted in 99.7% suspended solids removal, 71.5% COD reduction, 68.2% BOD reduction, 100% oil and grease removal and 91% TKN removal. In pilot plant pretreatment, the percentage recovery of water was 83.3%, and 99.7% sludge was recovered after dewatering in a filter press. Copyright © 2006 Society of Chemical Industry     

Decision model for coagulant dosage using genetic programming and multivariate statistical analysis for coagulation/flocculation at water treatment process

In this research, genetic programming and multivariate statistical analysis techniques have been applied for decision support on the coagulant dosage and the mixing ratio as two kinds of coagulants have been injected at the same time in the coagulating sedimentation process of water treatment. The coagulant dosage has typically been determined through the Jar-test, which requires a long experiment time in a field-water treatment plant. It is difficult to efficiently determine the coagulant dosage since water quality changes with time. As there are no human experts who have sufficient knowledge and experience in the field, coagulants may be injected with an improper mixing ratio, which causes poor performance in the coagulating sedimentation process. In this study, a model for the approximation of coagulant dosage has been developed using genetic programming (GP). The performance of this model was evaluated through validation. A guideline on the optimal mixing ratio between PACS (Poly Aluminum Chloride Silicate) and PAC (Poly Aluminum Chloride) has been provided through statistical analysis.     

Influence of Preozohation on Clarification by Flotation for Drinking Water Treatment

A preozonation study has been done at the potable water treatment plant of Moulle, in the North of France. The water is particularly rich in organic matter, with also algal blooms every, year, so the coagulan t treatmen t dose which is necessary for an optimal treatment, is very high. Previous laboratory tests have shown the importance of a preoxidation step, before the coagulation–flocculation–sedimentation industrial treatment line. It is also well known that flotation permits a significant reduction of coagulant dose. In addition, prechlorination of a water containing a large amount of organic matter induces the formation of a relatively high concentration of haloforms.     

混凝法强化城市污水一级处理试验

以济南市水质净化一厂初沉池进水为试验水样,在设定的反应条件下,以三氯化铁、聚合氯化铝、聚合氯化铁铝为试验混凝剂,以浊度、COD、TP、TN等为测定指标,进行了大量的烧杯搅拌试验。并在此基础上进行了无机混凝剂与有机混凝剂复配的正交试验。试验结果显示：最佳混凝剂为聚合氯化铁铝,其最佳投药量为25mg／L左右;去除率浊度在90％以上．、COD70％-90％、TP70％-95％、TN、NH3-N分别在30％和15％左右;正交试验最佳复配模式为：先投加无机混凝剂聚合氯化铁铝20mg／L,再投加有机混凝剂阴离子聚丙烯酰胺1．0m2／L。     

Evaluation of mixing conditions using an on-line monitoring technique

Effects of mixing conditions on flocculation were investigated by using a photometric dispersion analyzer (PDA) as an on-line monitoring technique in this study. Both river water and synthetic waters of humic acid (HA) and kaolin solutions were used and polyaluminum chloride (PACl) were used as a coagulant in this study. A clear relationship between F-index and residual turbidity was observed. Residual turbidity was low at high F-index. The mixing effects were also found closely related to the floc formation. When the floc formation was governed by a combination of charge neutralization and sweep floc, rapid mixing was important, but it was not important when the floc formation was governed by the sweep floc mechanism. The coagulant dosage governed the floc size and strength in the sweep floc region. The higher the coagulant dosage was, the larger but the weaker the floc was. Rapid mixing effects were different, depending on raw water characteristics. Fast and large floc formation was observed in flocculation of the kaolin solution, compared to that of the HA solution. Small HA would be mostly adsorbed onto the hydroxide precipitate after the precipitate formed. The adsorption could retard further floc growth. The resulting floc was small, and the floc formation was slow. However, kaolin helped flocculation by bridging the hydroxide precipitates, leading to fast and large floc formation. Temperature affected the flocculation kinetics as well as the floc size. A large floc formed at high temperature. The flocculation kinetics became fast with increasing temperature.     

Ca(OH)_2-CaCl_2沉淀法处理核工业高氟废水

为强化石灰沉淀法处理高氟废水时混合液的沉降性能,采用烧杯试验,分别考察了药剂投量、混凝剂投量、药剂投加顺序、原水F-浓度等因素对泥水分离性能的影响。研究表明,联合投加Ca(OH)_2和CaCl_2处理F-在5 000~10 000 mg/L的废水时,自絮凝会显著改善混合液沉降性能和出水浊度,而投加混凝剂的效果却有限。先Ca(OH)_2后CaCl_2的投加方式(二步法)比药剂同时投加(一步法)对沉降性能有较大的改善。运用分步加药法在中试规模的同程水平流斜板沉淀池实现了良好的固液分离效果。     

Enhanced Coagulation/Flocculation by Combining Diatomite with Synthetic Polymers for Oily Wastewater Treatment

The objectives are to evaluate the feasibility of treating oily wastewater using synthetic polymers (polyaluminum chloride (PAC), polyferric sulfate (PFS), and polyacrylamide (PAM)) combined with natural diatomite and to refine the operating parameters using diatomite as an adsorbent and a coagulant aid. The enhanced coagulation/flocculation by combining PAC with diatomite was investigated through mechanism analysis compared to the combination of PFS/PAM with diatomite, respectively. The effects of coagulant dose, initial pH, and settling time on chemical oxygen demand (COD) and turbidity were studied using PAC-diatomite in comparison with using PAC only. The enhanced coagulation/flocculation of diatomite with PAC was better than that with PFS/PAM in terms of COD/turbidity removal and floc settling characteristics, considering costs. The PAC-diatomite system reduced more than 70% of COD and 90% of turbidity over a wide pH range (7–10) within 20 min, with the optimum dose of PAC 50 mg/l and diatomite 1250 mg/l. The added diatomite effectively saved over 85% of PAC dose and simultaneously increased over 50% of COD removal efficiency. This study provided a novel and economical approach for diatomite utilization in the treatment of oily wastewater, satisfying the demands of reuse or reinjection into the ground.     

O3/H2O2联用工艺深度处理制浆造纸废水的试验研究

制浆造纸废水对水环境的污染十分严重,对其进行深度处理,势在必行,同时对废水深度处理技术的研究和应用也有着重要的意义。本文采用O3/H2O2工艺深度处理制浆造纸废水,考察了臭氧氧化法以及臭氧和过氧化氢联合工艺对废水COD、色度的去除效果和影响因素。结果表明,采用O3/H2O2联合工艺深度处理制浆造纸废水,效果显著,最终可将废水COD从300 mg.L-1降至95.250 mg.L-1,色度由350倍降至4倍以下,出水浊度小于5 NTU基本达到污水回用标准。