混合化工废水混凝脱色实验研究

对混合化工废水分别用聚铝、聚铁等无机混凝剂和有机高分子絮凝剂进行混凝脱色实验，并分析了脱色机理。实验表明,脱色剂性质、脱色剂投药量对处理效果都有很大影响。通过比较,可以根据混合化工废水不同的进水水质情况,选择适当的絮凝脱色剂，使出水色度大大降低,经济而有效。     

Application of combined coagulation-ultrafiltration membrane process for water treatment

The objectives of this research are to identify the membrane fouling potential due to different fractions of NOM and correlate the physicochemical properties of NOM and membranes with the adsorption of humic substances on membrane and investigate the mechanism of coagulation affecting UF, and find the optimum conditions of the combined of coagulation with UF membrane filtration for NOM removal. For Nakdong river water, the humic acid fraction was the most reactive precursor fraction for the formation of the ratio of THMFP/DOC (STHMFP) and TOXFP/DOC (STOXFP). The result of adsorption kinetics tests showed that hydrophobic organics adsorbed much more quickly than hydrophilic organics on both membranes. Thus, hydrophobic compounds exhibited a preferential adsorption onto membrane. In case of the effect of membrane properties on the adsorption of organic fractions, the adsorption ratio (C₁/C_e) was greater for the hydrophobic membrane than for the hydrophilic membrane regardless of the kind of organic fractions. For combined coagulation with membrane process, flux reduction rate showed lower than the UF process alone. Also, the rate of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying the coagulation process before membrane filtration showed not only reduced membrane fouling, but also improved removal of dissolved organic materials that might otherwise not be removed by the membrane. That is, during the mixing period, substantial changes in particle size distribution occurred under rapid and slow mixing conditions due to the simultaneous formation of microflocs and NOM precipitates. Therefore, combined pretreatment using coagulation (both rapid mixing and slow mixing) improved not only dissolved organic removal efficiency but also DBP (Disinfection By-Product) precursor's removal efficiency.     

Stabilization of PCC dispersions prepared directly in the mother-liquid after synthesis through the carbonation of (hydrated) lime

Various CaCO₃-based products are often used in the form of concentrated aqueous dispersions. This study investigates the stabilization of PCC dispersions prepared directly in the mother-liquid after the carbonation of (hydrated) lime through the adsorption of a commercial sodium polyacrylate dispersant. The results demonstrate that the composition of the mother-liquid, particularly the Ca²⁺ activity, profoundly influences virtually all processes pertinent to dispersion stabilization—from the initial charging of the CaCO₃ surface in base PCC dispersions, to the surface charge regulation and dispersion stabilization efficiency of the polyacrylate dispersing agent. Rising prominence of the counterion condensation effects in Ca²⁺ rich solutions limits the conditions conducive to the surface charge regulation through dispersant adsorption to an optimum pH range of about 8-11. Furthermore, dispersion stability analysis, based on the classical DLVO theory of colloid stability, and corroborated by experimental evidence in the form of particle size distribution analyses, also indicates that optimum stability conditions for such PCC dispersions are established with small dispersant doses (0.25-0.5% per dry weight) in the pH range of about 9-11.     

Evaluation of wastewater reclamation processes in a high-tech industrial park

The objectives of this research were to evaluate two different processes using for wastewater reclamation in a hightech industrial park area in Taiwan. The major units of the first AC-RO-IE system included sand filter, an activated carbon (AC) bed, microfiltration module, a reverse osmosis (RO) membrane and ionic-exchange (IE) columns. The second DAF-AC-RO system was comprised of coagulation/flocculation, dissolved air flotation (DAF), an activated carbon bed, microfiltration module and reverse osmosis membrane units. This study was carried out at a pilot-scale plant in situ that operated for approximately 1 year. According to the long-term experimental results, both the AC-RO-IE and the DAF-AC-RO processes illustrated excellent performances on inorganic and organic contaminant removal. Comparing the removal efficiency of the filtration-AC units in the AC-RO-IE system with the coagulation-DAF-AC units in the DAF-AC-RO system, the removal efficiency of TDS, SiO₂ and COD increased by 19.8%, 70.1% and 44.4% in the latter system, respectively. In addition, the combination of PAC-coagulation and DAF units could improve hardness removal, modify the form of dissolved silica, and reduce the SDI and MFI values. It showed good potential as a pretreatment unit in wastewater reclamation processes. Therefore, based on the reclaimed wastewater quality and process operational stability, the DAF-AC-RO system was suggested as a potential process for further application.     

The Preozonation of Phenolic Aqueous Solution and Its Effect on the Improvement of Coagulation Treatment

Phenolic solutions are difficult to treat with coagulation processes because phenol is well soluble in water. However, with suitable preozonation, the ozonized organic components can be removed more effectively by coagulation processes. In order to avoid excessive preozonation, a good control on the degree of preozonation is crucial for practical applications. The degree of preozonation of phenolic solution was evaluated by measuring the phenol decomposition rate, ADMI value and ozone outlet concentration during the ozonation. Three characteristic times were observed, namely (1) ADMI value reaches the peak value during preozonation, (2) the ozone outlet concentration starts increasing, and (3) the ADMI value reaches the discharge standard (500 value, EPA Taiwan). These characteristic times provide the useful means as real-time control parameters on the extent of preozonation. The results of HPLC and GPC show that phenol is almost completely decomposed after 43?min of preozonation. The major components after preozonation are oxalic acid and coupling compounds. The preozonized solution, containing phenol decomposition products, was then subjected to coagulation treatments. The coagulation behavior of preozonized solution is dependent on the extent of preozonation. Three types of coagulant were investigated, namely alum, ferric chloride (FeCl₃) and poly aluminum chloride (PAC). Both PAC and FeCl₃ are effective coagulants for COD removal. As an example, phenol solution (initial phenol concentration=300?mg/L, C _{O 3},i=20?mg/L) was preozonized for 50 minutes, followed by FeCl₃ coagulation treatment. After preozonation and coagulation processes, the total COD and ADMI removal rates are as high as 70% and 80%, respectively. Most of the coupling compounds and oxalic acid are removed by the coagulant.     

Process development for the removal of copper from wastewater using ferric/limestone treatment

The removal of copper from wastewater by ferric/limestone coagulation followed by screen filtration was carried out at a laboratory scale. The optimum coagulant (FeCl₃) dose and working pH were 50 mg// of Fe(m) and pH 7.5, respectively, through jar tests. For the efficient removal of copper from wastewater, we developed a novel process including the co-precipitation of copper with FeCl₃, alkalization in a limestone aeration bed, and separation of precipitates in a sedimentation tank coupled with internal stainless steel screen filter. The performance results showed that removal of copper from the solution was over 99.5%. The pH was effectively maintained over 7.5 in limestone bed during the whole process. Ferric hydroxide/copper aggregates were removed over 99% by stainless steel screen filter of 1,450 mesh. Periodic air backwashing alleviated fouling of the filter surface.     

Analysis of four Monte Carlo methods for the solution of population balances in dispersed systems

Monte Carlo (MC) constitutes an important class of methods for the numerical solution of the general dynamic equation (GDE) in particulate systems. We compare four such methods in a series of seven test cases that cover typical particulate mechanisms. The four MC methods studied are: time-driven direct simulation Monte Carlo (DSMC), stepwise constant-volume Monte Carlo, constant number Monte Carlo, and multi-Monte Carlo (MMC) method. These MC's are introduced briefly and applied numerically to simulate pure coagulation, breakage, condensation/evaporation (surface growth/dissolution), nucleation, and settling (deposition). We find that when run with comparable number of particles, all methods compute the size distribution within comparable levels of error. Because each method uses different approaches for advancing time, a wider margin of error is observed in the time evolution of the number and mass concentration, with event-driven methods generally providing better accuracy than time-driven methods. The computational cost depends on algorithmic details but generally, event-driven methods perform faster than time-driven methods. Overall, very good accuracy can be achieved using reasonably small numbers of simulation particles, O(10³), requiring computational times of the order 10²−10³ s on a typical desktop computer.     

混凝-Fenton氧化联合工艺处理有机废水的试验研究

利用多种方法联合处理是废水处理技术的发展方向,通过单因素实验确定了Fenton氧化和混凝处理高浓度有机废水的最佳参数,并进行了联合工艺处理该废水的实验。结果表明:采用Fenton-混凝联合工艺处理高浓度有机废水优于混凝-Fenton法,处理后苯酚含量、CODCr和浊度分别为45.2mg/L、818.2 mg/L和0.1 NTU,去除率分别为95.5%、60.1%和99.9%。     

Estimating the Removal of Anthropogenic Organic Chemicals from Raw Drinking Water by Coagulation Flocculation

A mathematical model was developed to estimate the efficacy of coagulation–flocculation treatment for removing neutral hydrophobic organic chemicals from raw drinking water. The model assumed that the only significant removal mechanism was the destabilization and settling of organic matter containing sorbed anthropogenic organic compounds. The model was validated with standard jar tests using compounds with a range of hydrophobicities (log?Kow = 1.89?to?5.48), including contaminant candidate list chemicals, pesticides, pharmaceuticals, and endocrine disrupting chemicals. Final concentrations of test compounds after coagulation and flocculation were in good agreement with model estimations for synthetic waters composed of Aldrich (Milwaukee, WI) humic acid solutions. The final compound concentrations in coagulated natural waters from two drinking water reservoirs were about 80% lower than those estimated with the model. Overestimations of treated water concentrations by the model were attributed to an increase in sorption by natural organic matter when coiled in aluminum hydroxide flocs, compared to sorption to dispersed natural organic matter in untreated water.     

Staged Coagulation for Treatment of Refractory Organics

Seasonal periods of high rainfall have been shown to cause elevated natural organic matter (NOM) loadings at treatment works. These high levels lead to difficulties in removing sufficient NOM to meet trihalomethane standards, and hence better alternative treatments are required. Here the removal of NOM was investigated by conventional coagulation treatment using both bulk and fractionated NOM. Initial experiments showed that over 70% removal of the hydrophobic and hydrophilic acid fractions was achieved at the works, while only 16% of the hydrophilic nonacid fraction was being removed. Bench scale jar testing of the isolated NOM fractions demonstrated that high removals of the hydrophobic fractions were achieved and that optimized conditions increased removal of the hydrophilic fractions, indicating that staged coagulation could be of benefit in the removal of the recalcitrant fractions. Experiments using optimized staged coagulation indicated that a small increase in the removal of the total NOM of this water was possible when compared to conventional treatment.