混凝工艺去除合流污水中有机物及营养元素

通过系列杯罐试验混凝处理合流污水,采用硫酸铝（Al₂(SO₄)₃）、硫酸铁（Fe₂(SO₄)₃）、聚合氯化铝（PAC）和聚合氯化铝铁（PAFC）4种混凝剂均能有效去除污水中的 TP、PO^3-₄-P、SS和COD。聚合金属盐（PAC和PAFC）混凝处理效果优于金属盐（Al₂(SO₄)₃和Fe₂(SO₄)₃）,达到相同的处理效果的投加量明显低于后者。助凝剂采用聚丙烯酰胺（PAM）、聚乙烯醇（PVA）、自制的高分子聚合物（AN）和活化硅酸（AS）,在保持较低混凝剂投加量的条件下可明显提高污水处理效果;添加助凝剂对强化PO^3-₄-P的去除作用不明显,PO^3-₄-P的去除仅与混凝剂的投加量相关。混凝剂和助凝剂对污水中NH₃-N的去除作用相对不显著。SS去除率随混凝剂投加量的变化趋势说明混凝的机理较为复杂,可能存在多种混凝机理共同作用。     

Coagulation-flocculation pretreatment of sanitary landfill leachates

Sanitary landfill leachates are considered as heavily polluted industrial wastewaters, presenting significant time and spatial variations of their physical-chemical parameters. Special care is required for their efficient treatment and disposal. The main aim of this work was to examine the application of coagulation-flocculation for the treatment of raw and partially stabilized leachates. Jar-test experiments were employed in order to determine the optimum conditions for the removal of organic matter and color, i.e. coagulant-flocculant combination, effective dosage and pH control. Ferric chloride, aluminium sulphate and lime were tested as conventional coagulants, whereas four commercial polyelectrolytes were co-examined: one anionic, two cationic and a non-ionic polymer. High chemical oxygen demand (COD) removal capacities (about 80%) were obtained during the addition of ferric chloride to the partially stabilized leachates, whereas low COD reductions (i.e. lower than 35%) were measured during the addition of coagulants in the raw samples. The addition of polyelectrolytes and pH adjustment in the alkaline region were found to affect slightly the removal of pollutants. The physico-chemical process may be used as a useful pretreatment step, especially for fresh leachates, prior to biological treatment, or as a post-treatment (polishing) step for partially stabilized leachates.     

Coagulant recovery from water treatment plant sludge and reuse in post-treatment of UASB reactor effluent treating municipal wastewater

In the present study, feasibility of recovering the coagulant from water treatment plant sludge with sulphuric acid and reusing it in post-treatment of upflow anaerobic sludge blanket (UASB) reactor effluent treating municipal wastewater were studied. The optimum conditions for coagulant recovery from water treatment plant sludge were investigated using response surface methodology (RSM). Sludge obtained from plants that use polyaluminium chloride (PACl) and alum coagulant was utilised for the study. Effect of three variables, pH, solid content and mixing time was studied using a Box–Behnken statistical experimental design. RSM model was developed based on the experimental aluminium recovery, and the response plots were developed. Results of the study showed significant effects of all the three variables and their interactions in the recovery process. The optimum aluminium recovery of 73.26 and 62.73 % from PACl sludge and alum sludge, respectively, was obtained at pH of 2.0, solid content of 0.5 % and mixing time of 30 min. The recovered coagulant solution had elevated concentrations of certain metals and chemical oxygen demand (COD) which raised concern about its reuse potential in water treatment. Hence, the coagulant recovered from PACl sludge was reused as coagulant for post-treatment of UASB reactor effluent treating municipal wastewater. The recovered coagulant gave 71 % COD, 80 % turbidity, 89 % phosphate, 77 % suspended solids and 99.5 % total coliform removal at 25 mg Al/L. Fresh PACl also gave similar performance but at higher dose of 40 mg Al/L. The results suggest that coagulant can be recovered from water treatment plant sludge and can be used to treat UASB reactor effluent treating municipal wastewater which can reduce the consumption of fresh coagulant in wastewater treatment.     

Removal of pesticides from surface waters by combined physicochemical processes. Part I: Dodine

The simultaneous action of powdered activated carbon and several coagulant agents on the removal of the fungicide dodine from spiked distilled water, was studied. As coagulants, ferric chloride (FeCl₃) and basic polyaluminium chlorosulfate ([Al(OH)_xCl_y(SO₄)_z]_n) were examined, using polyacrylamide, in certain cases, as coagulant aid (polyelectrolyte). The efficiency of dodine removal was investigated with respect to the added amount of powdered activated carbon (PAC), the pH value, as well as the type and dose of coagulant and polyelectrolyte. The experiments were performed applying the standard jar-test procedure. The initial concentration of dodine was 250 μg/L. At this concentration and pH range 5–8 it was found that a dose of 100 mg/L PAC was necessary to achieve more than 98% removal of dodine, whereas lower removal (91–93%) was obtained applying half the dose of PAC under the same conditions. However, when 10–100 mg/L FeCl₃ were simultaneously added with PAC, the removal efficiency increased to >98%, even with the half PAC dose.     

Enhanced coagulation of ferric chloride aided by tannic acid for phosphorus removal from wastewater

Phosphorus removal from wastewater is of great importance. In the present study, ferric chloride was selected as the coagulant, and tannic acid (TA), a natural polymer, as the coagulant aid to develop an effective coagulation process with the emphasis of phosphorus recovery from different types of wastewater. The results showed that TA can accelerate the settling speed by forming flocs with large size, reduce the residual Fe(III) to eliminate the yellow color caused by Fe(III), and slightly increase the phosphorus removal efficiency. The precipitate formed by TA-aided coagulation showed the advantage of releasing phosphorus faster than ferric phosphate, indicating the possibility of phosphorus recovery from wastewater as slow release fertilizer. To further understand the structural characteristics of the precipitate, analytical techniques such as Raman spectroscopy, X-ray photoelectron spectroscopy and matrix-assisted laser desorption ionization-time of flight mass spectrometry were employed. The analytical results indicated that TA–Fe–P complex was formed during the coagulation/flocculation processes. Solid phase in the precipitate consisted of TA–Fe–P complex, Fe–TA complex and/or ferric hydroxyphosphate.     

The application of novel coagulant reagent (polyaluminium silicate chloride) for the post-treatment of landfill leachates

Relatively "old" (stabilized) landfill leachates are a special category of wastewaters, which are difficult to treat further, mainly due to their bio-refractory organic content (humic substances). In this study, coagulation-flocculation was examined as post-treatment method for the biologically pre-treated stabilized leachates. The purpose was to examine the coagulation performance of alternative coagulant agents, i.e. the composite coagulant polyaluminium silicate chloride. Composite coagulants with different Al to Si molar ratio and different preparation methods were tested. Their efficiency was evaluated by monitoring from turbidity and phosphate content, other parameters strongly correlated with the presence of organic matter, such as UV absorbance at 254nm, COD and colour. The results suggest that the silica-based coagulants exhibit better coagulation performance, than the relevant conventional coagulant (alum) or simple pre-polymerized coagulants (PACl). Polyaluminium silicate chloride has greater tolerance against pH variation than alum or PACl, whereas this novel coagulant works better at pH values between 7 and 9. Coagulation-flocculation has proved to be an efficient post-treatment method for the biologically pre-treated leachates, promoting the removal of the refractory humic substances, while the treatment efficiency of coagulation can be improved by the application of the new coagulant agent.     

Preparation and application of a new composite chitosan flocculant

A new composite chitosan flocculant has been prepared, and its optimal dosage in the treatment of sewage established. It significantly improves the removal of chemical oxygen demand, suspended solids and aluminium ions from water. Compared with the traditional flocculant polyaluminium chloride, the cost of the composite flocculant was lower and it produced less pollution.     

混凝沉淀法处理含砷选矿废水

某钨矿含砷选矿废水砷含量高且砷以As(V)为主要存在形态,采用混凝沉淀法处理,详细考察了生石灰、硫酸亚铁和六水三氯化铁3种混凝剂对废水中砷的去除效果。实验结果表明,在PAM投加量40 mg/L,静沉时间60 min条件下,比较分析3种混凝剂对砷的去除效果,三氯化铁为最佳除砷混凝剂。三氯化铁最佳除砷工艺条件为:pH 7.5,三氯化铁投加量986.67 mg/L,混凝反应时间25 min,PAM投加量为40 mg/L,静沉60 min,含砷选矿废水经该工艺处理后,砷去除率可达99.14%,出水砷浓度降至0.361 mg/L,达到国家污水综合排放标准(GB8978-1996)。     

聚硅硫酸铁混凝去除石化废水二级出水中有机污染物的研究

采用聚硅硫酸铁(PFSiS)混凝剂对石化废水二级出水进行了强化混凝实验,考察其对有机污染物的去除效果,并对不同时期的絮体微观结构进行了研究。结果表明,PFSiS可有效去除水中COD,当PFSiS投加量为40 mg/L(以Fe计),静置时间为120 min,COD去除率可达50%左右;絮体的微观结构为空间网状结构,随静置时间的延长,絮体密实程度提高,颜色加深。     

强化混凝工艺深度处理给水厂排泥废水

水厂废水的综合处理与回用是我国供水行业的新趋势和节水目标所在,采用强化混凝技术进行水厂排泥废水的深度处理。通过混凝剂筛选实验和有机物表征确定最佳混凝剂为高效聚合铝(HPAC),适宜投加量为650 mg/L。当混凝剂HPAC投加量为650 mg/L时,对COD、TOC、浊度和色度的去除率分别为82.5%、89.8%、95%和92.5%,相应的出水值分别为58 mg/L、8.46 mg/L、2.35 NTU、13度,COD满足《污水综合排放标准》(GB 8978-1996)的要求(COD≤100 mg/L),同时实验结果显示聚合氯化铝(PAC)、HPAC、三氯化铁(FeCl3)主要去除分子量处于>1 300 Da范围的有机物,对分子量处于744～1 300 Da之间的有机物去除有限。     

Influence of some additives to aluminium species distribution in aluminium coagulants

Aluminium ions hydrolyse and polymerise into different species in water. Main aluminium species in aluminium coagulant solutions are monomeric Al species (Al1) and polymeric Al species Al13O4(OH)24(7+) (Al13). The aluminium species distribution in coagulant solutions can be influenced by many parameters. This paper studies influences of concentrations of total aluminium species (Al(t)) and other species--OH-, polysilicic acid and ferric species, which were added in aluminium coagulant solutions, on the aluminium species distribution through 27Al nuclear magnetic resonance (NMR) analysis. Results show that only Al1 and no Al13 exist in coagulant solutions at higher Al(t) concentrations (over 1 mol l(-1)), while both species exist at lower Al(t) concentrations (0.1 mol l(-1)). The increase of OH/Al value (molar ratio) increases the concentration of Al13 in coagulant solutions, while the addition of polysilicic acid and ferric species decreases the concentration of Al13.     

Determination of optimum polymeric coagulant in palm oil mill effluent coagulation using multiple-objective optimisation on the basis of ratio analysis (MOORA)

The main limitation of a conventional palm oil mill effluent (POME) ponding system lies in its inability to completely decolourise effluent. Decolourisation of effluent is aesthetically and environmentally crucial. However, determination of the optimum process parameters is becoming more complex with the increase of the number of coagulants and responses. The primary objective of this study is to determine the optimum polymeric coagulant in the coagulation–flocculation process of palm oil mill effluent by considering all output responses, namely lignin–tannin, low molecular mass coloured compounds (LMMCC), chemical oxygen demand (COD), ammonia nitrogen (NH₃-N), pH and conductivity. Here, multiple-objective optimisation on the basis of ratio analysis (MOORA) is employed to discretely measure multiple response characteristics of five different types of coagulants as a function of assessment value. The optimum coagulant is determined based on the highest assessment value and was identified as QF25610 (cationic polyacrylamide). On the other hand, the lowest assessment value was represented by AN1800 (anionic polyacrylamide). This study highlights the simplicity of MOORA approach in handling various input and output parameters, and it may be useful in other wastewater treatment processes as well.     

Evaluation of modified clay coagulant for sewage treatment

The use of modified clays as coagulants for sewage treatment was investigated in this study. The raw clays were montmorillonites K10 and KSF, and were modified by polymeric Al or Fe and/or Al/Fe mixing polymeric species. The comparative performance of modified clays and aluminium sulphate and ferric sulphate were evaluated in terms of the removal of turbidity, suspended solids, UV(254)-abs, colour, and total and soluble CODs. The results demonstrated that after being modified with mixing polymeric Al/Fe species, two montmorillonite clays possess greater properties to remove the particles (as suspended solids) and organic pollutants (as COD and UV(254)-abs) from the sewage and to enhance the particle settling rate significantly.     

玉米深加工废水的混凝实验

在室温条件下,分别选用聚合氯化铝(PAC)、聚合氯化铝铁(PAFC)及三氯化铁(FeCl3)对玉米深加工废水进行混凝实验。综合考虑各种混凝剂对磷、COD以及SS的去除效果,最终选取PAC作为混凝剂。采用PAC和聚丙烯酰胺(PAM)作为复合混凝剂,对其去除效果做进一步研究,并确定了最佳投加量及pH值。实验结果表明,在PAC投加量25mg/L,PAM投加量0.5 mg/L,pH为8条件下,混凝效果最佳。磷、COD、SS去除率可分别达到90.1%、53.3%和88.2%,对应的出水质量浓度分别为0.41、26.8和2 mg/L。     

聚合氯化铝污泥对磷的吸附动力学及热力学

聚合氯化铝污泥（polyaluminium chloride sludge,PACS）是指以聚合氯化铝（PAC）为混凝剂的城镇给水厂在生产过程中所产生的污泥。采用批量吸附实验考察了PACS对磷的吸附动力学及热力学行为。结果表明,吸附反应发生1 h后,PACS对磷的吸附量达到平衡吸附量的75%～90%,随后PACS对磷的...     

铁铝复配混凝剂处理低温低浊水

针对北京某水库水在冬季呈现低温低浊特性,以此为原水的某水厂在该期间常会出现出水余铝超标现象的问题,通过烧杯实验研究不同投药量下聚合氯化铝(PAC)以及它与三氯化铁(FeCl3)不同复配比形成混凝剂对冬季北京某水库水的处理效果。结果表明,复配药剂存在最佳的Fe/Al摩尔复配比为1/5,此时余铝、有机物去除效果较其他配比混凝剂高。在此配比下,当PAC投药量为0.03 mmol/L时,水中残余铝量取得最低值0.0063 mg/L。相同投药量复配药剂的浊度去除效果比单独使用PAC的浊度去除效果略弱。当投药量为0.06 mmol/L时,Fe/Al摩尔比为1/5的复配混凝剂,能使浊度降至0.4 NTU左右。此外,复配药剂的投药量小,投药范围更宽,易于实际投药操作;同时复配药剂还适于常温及偏中性水源水的处理。规模为5 m3/h中试实验也证明,采用铁铝复配混凝剂连续运行,可获得良好的浊度、余铝去除效果。     

混凝强化除磷的模拟实验研究

以模拟污水为研究对象,考察了不同絮凝剂(聚合氯化铝、三氯化铁及硫酸亚铁)对污水中磷的去除效果及其影响因素,并对氢氧化铁的吸附除磷规律,以及氢氧化铁与絮凝剂复配除磷的效果进行了探讨,提出了聚合氯化铝、三氯化铁及硫酸亚铁可行的投加量.     

PAFC对水体中持久性有机污染物PFOA的混凝效果

针对含全氟辛酸(PFOA)的工业废水及应对PFOA的污染突发事件,采用PAFC及其复配粘土矿物凹凸棒和沸石进行混凝实验,并对几个影响因素进行了考察。结果表明,在PAFC的最佳投加量10 mg/L时,PFOA和浊度的去除率分别达到70.25%和99.42%,PAFC混凝处理PFOA的效果优于PAC;pH值对PAFC去除PFOA有一定的影响,当pH大于6时有利于PFOA的去除;PFOA和浊度的去除率随原始浊度的增加而增加;活性炭、盐酸改性凹凸棒、盐酸改性沸石、CT-MAB改性的沸石复配PAFC均可提高PFOA的去除率;改性处理后的沸石应用于PFOA的处理中,有望降低处理成本。     

A modified UCT method for biological nutrient removal: configuration and performance

A pilot-scale prototype activated sludge system is presented, which combines both, the idea of University of Cape Town (UCT) concept and the step denitrification cascade for removal of carbon, nitrogen and phosphorus. The experimental set-up consists of an anaerobic selector and stepwise feeding in subsequent three identical pairs of anoxic and oxic tanks. Raw wastewater with influent flow rates ranging between 48 and 168 l d(-1) was fed to the unit at hydraulic residence times (HRTs) of 5-18 h and was distributed at percentages of 60/25/15%, 40/30/30% and 25/40/35% to the anaerobic selector, 2nd and 3rd anoxic tanks, respectively (influent flow distribution before the anaerobic selector). The results for the entire experimental period showed high removal efficiencies of organic matter of 89% as total chemical oxygen demand removal and 95% removal for biochemical oxygen demand, 90% removal of total Kjeldahl nitrogen and total nitrogen removal through denitrification of 73%, mean phosphorus removal of 67%, as well as excellent settleability. The highest removal efficiency and the optimum performance were recorded at an HRT of about 9h and influent flow rate of 96 l d(-1), in which 60% is distributed to the anaerobic selector, 25% to the second anoxic tank and 15% to the last anoxic tank. Consequently, the plant configuration enhanced removal efficiency, optimized performance, saved energy, formed good settling sludge and provided operational assurance.     

絮凝剂对高速厌氧反应器污泥颗粒化的强化作用

以考察絮凝剂对厌氧反应器中活性污泥性能的影响为目的,将聚合氯化铝(PAC)、聚丙稀酰胺(PAM)、聚季铵盐3种不同类型絮凝剂以不同投加量添加到反应器中,采用生物化学甲烷势(BMP)和厌氧毒性测定(ATA)分析方法,评价了3种絮凝剂的厌氧生物可降解性以及3种絮凝剂对厌氧污泥产甲烷活性、沉降性能等方面的促进或抑制作用。确定以聚季铵盐作为厌氧污泥颗粒化促进剂,建议采用多次投加方式,反应器中聚季铵盐质量浓度以10-50mg／L为宜。