Polyaluminum Chloride Coagulation Research Articles

Treatment of dairy wastewater by inorganic coagulants: Parametric and disposal studies

Present study reports treatment of simulated dairy wastewater (SDW) by inorganic coagulants such as poly aluminum chloride (PAC), ferrous sulphate (FeSO 4) and potash alum (KAl(SO 4) 2·12H 2O). Batch coagulation experiments were conducted to evaluate the influence of initial pH ( pH i : 5–10) and coagulant dosage ( m: 100–5000 mg/L) on chemical oxygen demand (COD) removal from SDW. Residual COD and system pH were observed as function of time. Optimum pH i ( pH i,op ) was found to be 8.0 for all the three coagulants. Optimum m ( m op ) was found to be 300, 800 and 500 mg/L for PAC, FeSO 4 and KAl(SO 4) 2·12H 2O, respectively, giving 69.2, 66.5 and 63.8% COD removal efficiency in 30 min. Heating values of the sludge generated by the coagulants PAC, FeSO 4 and KAl(SO 4) 2·12H 2O were found to be 20.7, 29.6 and 17.3 MJ/kg, respectively.

PACl coagulation for the solid-liquid separation of highly concentrated algae suspensions

The ability of algae to absorb CO2, a greenhouse gas, for photosynthesis has received considerable attention in recent years due to the possibility of growing algae to extract into bio-energy. Therefore, technology that rapidly separates and recovers an algal mass from water is needed. In this study, the coagulant polyaluminum chloride (PACl) with high basicity (B) was applied as a chemical coagulant in a Jar Test for a solid-liquid separation study using two algal species, Chlorella sp. and Spirulina sp., suspended in both freshwater and seawater. The coagulation process was monitored using an on-line photo-turbidimeter to examine the effect of chemical dosage and operating conditions on solid-liquid separation efficiency. Experimental results demonstrate that, for the 200 NTU suspension, Spirulina sp. required a much higher PACl dosage than Chlorella sp. for effective coagulation owing to the higher negative surface charge of the Spirulina sp. Additionally, a wide range of dosages achieved effective coa...

Treatment with chemical coagulants at different dosing levels changes ecotoxicity of stormwater from the Tahoe basin, California, USA

In recent decades, the transport of stormwater-associated fine particles and phosphorus into Lake Tahoe has led to decreased water clarity and related ecological changes. Polyaluminum chloride coagulants (PACs) have shown great promise in removing these constituents from stormwater before it enters the lake. However, the potential risks of coagulant treatment to aquatic organisms are not well understood. This study investigated stormwater and coagulant toxicity under non-dosed, optimally-dosed, and over-dosed conditions using the US EPA 3-species test through growth of green algae (Selenastrum capricornutum), zooplankton (waterflea, Ceriodaphnia dubia) mortality and reproduction, and larval fish (fathead minnow, Pimephales promelas) mortality and biomass. Stormwater samples were collected during a 2005 spring snowmelt runoff event from three sites representing various forms of developed regions around Lake Tahoe. Samples were dosed with two different coagulants (a chitosan and a PAC) at levels optimized with a streaming current detector (SCD). Non-treated highway runoff was toxic to zooplankton and fish. Optimal coagulant dosing increased algal growth and reduced zooplankton toxicity. Overdosing at two and three times the optimal level of a PAC decreased zooplankton reproduction and increased fish mortality. PAC-related toxicity was correlated with increasing total unfiltered aluminum and decreasing alkalinity, pH, and DOC. Because of toxicity risks, we recommend keeping PAC coagulant dosing at or below optimal levels in practice.

Fractal characteristics of particle size distribution in dynamic flocculation process

This study selected polyaluminum chloride(PAC) coagulant to remove suspended particles in Kaolin suspension solution and used a turbidimeter and particle counter to monitor the flocculation process online and collected the experiment data. The experiments were conducted to study the dynamic distribution characteristics of suspended particles under different hydrodynamic conditions. The results show the self-similarity and scale invariance of particle size distribution. The study further proposed the concept of fractal dimension of particle size distribution and found out that fractal dimension changed in a similar way as residual turbidity did and could excellently indicate the variation of coagulation effect. Therefore, fractal dimension could be adopted to optimize the addition of coagulants and the quality of outflow could be further improved to reduce production costs.

Optimizing the coagulant dose to control membrane fouling in combined coagulation/ultrafiltration systems for textile wastewater reclamation

Optimal coagulation conditions need to be re-examined when coagulation is coupled to membrane filtration for wastewater treatment. This work focused on the optimization of coagulant dosing in order to control membrane fouling in ultrafiltration (UF), following coagulation for the reclamation of textile wastewater. The effects of pore size and coagulant types and dosages on flux decline were investigated using a stirred-cell UF unit. The flux was greatly enhanced for the UF membrane when a coagulant was added, whereas for the microfiltration (MF) membrane the flux decreased. This could be attributed to changes in the size of coagulated particles and their interaction with membrane pores. At a low dosage (e.g., 0.0371 mM as Al), the polyaluminum chloride (PACl) coagulant was found to control the flux decline most effectively for low ionic-strength wastewater. The optimal dose minimized the fouling and cake layer resistances, although it was sharp and dependent on influent composition. The cake layer protected the membrane from fouling, but it provided additional resistance to permeation. Analyses of turbidity, particle size, and membrane surface exhibited the characteristics of coagulated particles and their cake structures that are closely associated with flux behavior.

The origin of Al(OH) 3-rich and Al 13-aggregate flocs composition in PACl coagulation

The composition of hydrolyzed Al species is essential for the understanding of coagulation with Al-based coagulants. Surface characteristics of flocs formed by coagulation with two distinct polyaluminum chloride (PACl) coagulants were identified. One commercial coagulant (PACl-C) with voluminous monomeric Al and colloidal Al(OH) 3 and a custom-made PACl (PACl-Al 13) containing high Al 13 content were applied to destabilize kaolin particles. The flocs formed by PACl-C and PACl-Al 13 at neutral and alkaline pH ranges, respectively, were observed by FE-SEM and HR-TEM. In addition, the Al composition of these flocs was characterized by XPS and HR-XRD, and the imaging of Al(OH) 3 precipitates and Al 13 aggregates were conducted by SEM as well as tapping mode AFM in liquid system. The observations of flocs indicate that the morphology of Al(OH) 3-rich flocs are fluffy and porous around the edge of flocs, while the Al 13-aggregate flocs have a glossy contour and irregular structure. Both Al(OH) 3-rich and Al 13-aggregate flocs do not possess well-formed crystalline structure except for the Al 13-like crystal exists in the Al 13-aggregate flocs. Among Al(OH) 3 precipitates, colloidal Al(OH) 3 is micro-scale in size, while amorphous Al(OH) 3 is nano-scale. During the formation of Al 13 aggregates, some coiled and clustered Al 13 aggregates with smoother surface were observed. The XPS study on floc surface showed that tetrahedral (Al IV) /octahedral (Al VI) Al ratio on the surfaces of PACl-C and PACl-Al 13 flocs is 1:1.6 and 1:9.9, respectively. Of the in situ formed Al 13, almost half of Al-hydroxide precipitates on the surface of Al(OH) 3-rich flocs possess the Al IV center. It also found that the irregularly aggregated Al 13 with a similar Al 13 crystalline structure subsists on the surface of Al 13-aggregate flocs.

Natural organic matter (NOM) removal in a typical North-China water plant by enhanced coagulation: Targets and techniques

Seasonal coagulation objectives for a typical North-China water treatment plant with micro-polluted and high alkalinity source waters are proposed in this paper. These are based on a yearlong data collection period where raw water characteristics, trihalomethanes formation potential (THMFP) and coagulation features were investigated using a jar test procedure, resin absorption and ultrafiltration fractionations. Three approaches beyond simply increasing the coagulant dose were used to achieve optimized coagulation. One is coagulation by adjusting the pH of the raw water when metal salt coagulants (FeCl 3 and AlCl 3) are used. At pH levels of about 5.0 for FeCl 3 and about 5.8 for AlCl 3, the highest removal of natural organic matter (NOM) was obtained, which is twice that without pH control. The second is enhanced coagulation through coagulant optimization based on raw water characteristics. A high efficient composite polyaluminum chloride (HPAC) coagulant was developed for the water taking the advantages of polyaluminum chloride (PACl) and other additives. HPAC exhibited 30% more efficiency than AlCl 3, FeCl 3 and polyaluminum chloride (PACl) in dissolved organic carbon (DOC) removal and was also very effective in turbidity removal. The third is enhanced softening with coagulant addition. Higher removal of NOM is achieved by enhanced softening with coagulant addition conditions as compared with conventional coagulation at natural pH. Especially with PACl addition, it can enhance the formation of Mg(OH) 2 precipitate and remove NOM efficiently at a relatively lower pH range (pH < 10). By this approach, the pH for enhanced softening can be decreased significantly into a practical operation pH range for high-hardness water at a treatment plant.

Adsorption of turbid materials by the cyanobacterium Phormidium parchydematicum

The present study investigated the adsorption of turbid materials such as clays, by microalgae. Among six tested microalgae, including Chlorophyceae and Cyanophyceae, a cyanobacterium, Phormidium parchydematicum strain KCTC 10851BP, and unicellular alga, Chlorella vulgaris strain UTEX 265, showed a higher turbidity-removal efficiency (TRE) of 99% and 93%, respectively, for clay-containing water after 24 h, which was much higher than the 36% for the control. The TREs of all the treatments were >95% after 24 h, except for the treatment with a lower algal density and optical density (OD) = 0.1. Phormidium parchydematicum demonstrated a slightly higher TRE than a polyaluminum chloride coagulant (Al13(OH)28Cl9SO4) for a turbid field water. Scanning electron microscope (SEM) observations revealed a dense adsorption of clay particles to the surface of P. parchydematicum. Thus, it would appear that P. parchydematicum and C. vulgaris can be used for clay removal in turbid water by sedimentation through microalgae–clay flocculation.

Natural organic matter removal by coagulation: effect of kinetics and hydraulic power

In this paper, the mechanism of NOM removal by coagulation is investigated using coagulant polyaluminium chloride (PACl), compared with AlCl3. The kinetics of Al ion hydrolysis, interaction of hydrolyzed species of Al and NOM, and hydraulic power condition in coagulation process are investigated by programmable jar test, photometric dispersion analyzer and ferron assaying. After the coagulant dosing, Al ion would hydrolyze very quickly, and then monomeric Al and small polymeric Al would further hydrolyze to form larger polymer and precipitate, based on pH condition, while the further hydrolyzed process is relative slow. Although complexation between NOM and Al appears to be several orders of magnitude slower than hydrolysis of monomeric forms of Al, it would be faster than further polymerization and precipitation of Al during aging. However the further polymerization of fresh Al would benefit to Al-NOM complex aggregation and settlement. Therefore, PACl, with stabile preformed polymer shows significantly different performance in NOM removal compared with AlCl3. Although the hydraulic power condition plays significant role in collision frequency and efficiency of particles removal, the process of the aggregation to form larger floc to settle down is relative slower than interaction of Al and NOM, and it is not very correlative to the performance of NOM removal if only it can provide enough mixture.

Purification and characterization of Al13 species in coagulant polyaluminum chloride

Nano-Al13 was separated and purified by four methods to investigate its characteristic, and was analyzed by Al-Ferron timed complexation spectrophotometer, 27Al-NMR (nuclear magnetic resonance), and transmission electron microscopy (TEM). Coagulation efficiency of nano-Al13, polyaluminum chloride (PAC), and AlCl3 in synthetic water were also investigated by jar test. The dynamic process and aggregation state of kaolin suspensions coagulating with nano-Al13, PAC, and AICl3 were also investigated. The experimental results indicated that the efficiency of gel column chromatography method was the highest for separating PAC solution with low Al concentration. Ethanol and acetone method was simple and could separated PAC solution with different Al concentrations, while silicon alkylation white block column chromatography method could separate PAC solution only with low Al concentration. The SO4(2-)/Ba2+ displacement method could separate PAC solution with high Al concentration, but extra inorganic cation and anion could be introduced into the solution during the separation. The coagulation efficiency and dynamic experimental results showed that nano-Al13 with a high positive-charged species was the main species of electric neutralization in coagulation process, and it could reduce the turbidity and increase the effective particles collision rate efficiently in coagulation process. Its coagulation speed and the particle size of coagulant formed were of greatest value in this study.

The use of polyaluminium chloride for removing colour, COD and ammonia from semi-aerobic leachate

This research examined various experimental conditions for application of Polyaluminium Chloride (PAC) for removing colour, COD and ammonia from semi-aerobic. The removals of colour, COD and ammonia were up to 93%, 56% and 32%, respectively, at an optimum dosage of 2000 mg/L PAC. Rapid and slow mixing speed played only a minor role in the removal efficiencies for colour, COD and ammonia. The flocs size distribution for PAC coagulant shows an increase in floc size with increasing coagulant dosages. PAC also exhibited excellent settling characteristics, with majority of the flocs settled out in the initial 5 min of settling.

FRACTIONATION OF SOLUBLE MICROBIAL PRODUCTS (SMP) AND SOLUBLE EXTRACELLULAR POLYMERIC SUBSTANCES (EPS) FROM WASTEWATER SLUDGE

Dissolved organic matter (DOM) in soluble microbial products (SMP), loosely bound (LBEPS) and tightly bound extracellular polymeric substances (TBEPS) were extracted from wastewater sludge, fractionated by size exclusion chromatography and characterized by ultraviolet absorbance at 230, 254 and 280 nm, the dissolved organic carbon (DOC) content and excitation‐emission‐matrix (EEM) spectra. The DOM of molecular weight (MW) > 20000 Da accounted for 33% of SMP, including proteins of high aromaticity, and 22% of both LBEPS and TBEPS, which were composed of organic acid‐like substances and proteins, respectively. Polyaluminum chloride (PACl) coagulation effectively removed this DOM fraction. Conversely, the DOM of MW < 1000 Da were mostly non‐aromatic organic acids (and possibly polysaccharides) of low aromaticity for SMP and both EPS, and removal by PAC1 coagulation was minimal. The findings indicated that the chemical characteristics of DOM in SMP and LBEPS were similar but not identical. The TBEPS and LBEPS exhibited significantly different DOM based on DOC distribution or EEM fingerprint.

Treatment Spent Filter Backwash Water using Dissolved Air Flotation (DAF) in Isfahan WTP

Recovering spent filter backwash water is currently receiving a great deal of attention. EPA published the Filter Backwash-Recycling Rule (FBRR) in 2001. Recycle stream may contain significant concentration of pathogens, such as, cryptosporidium and Giardia. Dissolved Air Flotation (DAF) was investigated as a possible technology alternative to simple or advanced sedimentation technology. In this study with using a pilot of DAF effluent turbidities of &amp;gt;20NTU could be easily obtained, when raw water turbidities were in excess of 800 NTU. Chemical requirements were low with only a single low dose of polyaluminium chloride (PACl) required binding the floc particles to form a solids matrix suitable for flotation. The results showed that the efficiency of continuous flow DAF with using PACl as coagulant for removal of Turbidity, COD, HPC, SS and MPN were 97, 72, 75, 95 and 100 percent, respectively. The statistical analyses indicated that the optimum saturation pressure is 4-5 atm, during recycle rate of 20-25 percent. The removal efficiencies of turbidity and bacteria in coagulation with sedimentation were reported up to 70 and 65 percent, while in this study using DAF with coagulant PACl could remove turbidity, COD, SS and bacterial up to 97,72, 95 and, 72 percent respectively.

Effect of coagulation pretreatment on membrane distillation process for desalination of recirculating cooling water

The objective of this work was to study the performance of coagulation pretreatment and the effect of coagulation pretreatment on membrane distillation (MD) process for desalination of recirculating cooling water (RCW). In this study, RCW was desalinated by MD process after pretreated by coagulation, precision filtration, acidification and degassing. Pre-coagulation of RCW with poly-aluminum chloride (PACl) coagulant improves the elimination of total organic carbon (TOC), total phosphorus (TP) substances. The optimized pH value and PACl dosage were 7 and 15 mg/L, respectively. Compared with MD process without coagulation pretreatment, much slighter MD flux decrease was observed when coagulation pretreatment was employed for desalination of RCW using MD process. Compared with the membrane flux of MD process for the RCW without coagulation pretreatment, about 23% improvement of MD flux was obtained by employing coagulation pretreatment after 30 days operation. The variation of crystal morphology on membrane surface and hydrophobic character of PVDF hollow membranes were investigated. The results show that distorted rhombic magnesium-calcite scale formed on membrane surface when coagulation pretreatment was employed. However, the deposited magnesium-calcite on the membrane surface was loosely packed with particles of much smaller size when RCW without coagulation pretreatment was fed. It is because that the coagulation pretreatment removed most of the natural organic matter (NOM) and antiscalant additives in RCW, which act as an inhibitor to calcium carbonate crystal growth in water. After coagulation pretreatment, bigger crystal deposit formed on membrane surface with the increase in CF of RCW. It was rather difficult for bigger crystal to enter membrane pores and thus the formation of bigger crystal reduced partial wetting of membrane, which enhanced trans-membrane flux. The hydrophobic character of PVDF hollow membranes used in MD process can be easily recovered by chemical rinsing using acid–base solutions. The results indicate that the pretreatment with chemical coagulant, PACl, is effective for the desalination of RCW by MD process.

Removal of disinfection by-products precursors by polyaluminum chloride coagulation coupled with chlorination

The effect of coagulation coupled with chlorination (i.e., pre-, inter-, and post-chlorination) on the formation of disinfection by-products (DBPs) and the removal efficiency of DBPs precursors were investigated. Compared with coagulation coupling with pre-chlorination, coagulation coupled with inter-chlorination could lead a higher removal efficiency of dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA) and chloroacetic acids formation potential (CAAsFP). The CAAsFP/DOC value of residual DOC showed that coagulation with inter-chlorination has a beneficial effect on CAAs precursors removal. More DBPs were produced during inter-chlorination than that of pre-chlorination at pH 7.5, while less DBPs were produced during inter-chlorination than that of pre-chlorination at pH 5.5. In addition, the precipitate of humic acid (HA) after coagulation was chlorinated to study the kinetics of chlorine decay. The results showed that coagulated-HA had a higher reactivity with chlorine than aqueous-HA at pH 7.5. Furthermore, the trends of zeta potential during coagulation process suggested that the distribution of chlorine species had significant influence on the removing of DBPs precursors by coagulation coupled with chlorination.

DISSOLVED AIR FLOTATION (DAF) FOR PRIMARY AND TERTIARY TREATMENT OF MUNICIPAL WASTEWATERS

ABSTRACT Tertiary treatment of municipal wastewater by dissolved air flotation was studied on a pilot‐scale. The effects of coagulant dose, flocculation pattern, dispersion water recycle ratio and hydraulic surface load on process performance were evaluated. The treatment of primary effluents by dissolved air flotation was investigated to assess the suitability of this process for the treatment of heavily polluted effluents and wastewater treatment plant by‐passes. The tertiary dissolved air flotation process typically achieved 90–99 % reductions in the numbers of enteric microbes (total coliforms, enterococci and F‐RNA coliphages). The average reductions of total phosphorus and chemical oxygen demand were 55–81 % and 28–39 %, respectively. Increasing the polyaluminium chloride coagulant dose from 2 to 10 mgAl3+ l−1 and the dispersion water recycle ratio from 11 to 22 % improved the efficiency of the process. Changes in the flocculation conditions (range of G‐values 10–55 s−1; retention time 4–8 min) and hydraulic surface load (5 or 10 m h−1) did not clearly affect the process efficiency. The dissolved air flotation process decreased the numbers of enteric microbes and reduced total phosphorus, chemical oxygen demand and suspended solids from the primary treated wastewaters on average by 98–99.8%, 90 %, 47% and 77 %, respectively. The dissolved air flotation process was demonstrated to be a suitable method for efficient tertiary treatment of wastewaters, as well as for the elimination of peak pollution loads or by‐pass wastewaters during the treatment plant overloading situations.

A Study on the Relative Performance of Different Coagulants and the Kinetics of COD in the Treatment of a Textile Bleaching and Dyeing Industrial Wastewater

Untreated wastewater from textile industries when discharged to nearby waterways would cause considerable health concerns to humans and animal life and to the host environment. They contain various chemicals such as dyes, detergents and surfactants, some of which are recalcitrant to biodegradation. Such wastewater can be better remediated by chemical treatment. The treatment of a textile bleaching and dyeing industrial wastewater was done by Coagulation and Flocculation Method using a jar test apparatus. Alum, polyaluminum chloride (PAC), and ferrous sulfate were used in separate runs as coagulants, while excelfloc 264 (a polyacrylamide copolymer) was used as flocculant. Preliminary tests were first conducted to determine the appropriate coagulation and flocculation agitation rates and settling time. The initial pH of the sample effluent was varied from 5 to 8 for alum coagulation, 5 to 8.5 for PAC coagulation and 9 to 11 for ferrous sulfate coagulation. The dosages of each coagulant and the excelfloc were varied from 200 to 1000 ppm, and 0.5 to 2.5 ppm, respectively. Experimental results showed that the optimum initial pH of the wastewater using alum, PAC, and ferrous sulfate were 7, 7.5, and 10, respectively. The optimum dosages of the coagulants were found to be 600ppm for alum and 800ppm for both PAC, and ferrous sulfate. The optimum flocculant dosages were 1.5ppm with alum, 1 ppm with PAC and 2ppm with ferrous sulfate. The highest percentage removal of COD, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), chromium, and color were found to be 58.55%, 65%, 36.51%, 76.45%, and 78.96%, respectively, using alum: 65.4%, 67.5%, 35.84%, 44.92%, and 75.49%, respectively using PAC; and, 55.72%, 34.16%, 33.95%, 19.88%, and 48.56%, respectively, using ferrous sulfate. Among the three coagulants tried, coagulation with PAC gave the highest percentage of COD removal of 65.64% and TSS removal of 67.5% while alum gave the highest removal of both chromium and color at 76.45% and 94.49%, respectively. Rapid and slow agitation rates used were 240rpm for 1 minute and 40rpm for 20 minutes, respectively; while settling time was 30 minutes. Kinetics of the COD removal was studied at the optimum conditions. Kinetic model, determined by curve fitting with the coagulation/flocculation reaction, was observed to follow a first-order rate of reaction.

Improvement of alum and PACl coagulation by polyacrylamides (PAMs) for the treatment of pulp and paper mill wastewater

A study using coagulation–flocculation method for the treatment of pulp and paper mill wastewater has been carried out. The efficiency of alum and polyaluminum chloride (PACl) when used alone and in coupled with cationic polyacrylamide (C-PAM) and anionic polyacrylamide (A-PAM) on the treatment of pulp and paper mill wastewater were studied. The reduction efficiency of turbidity and chemical oxygen demand (COD), removal efficiency of total suspended solids (TSS), sludge volume index (SVI) and settling time are the main evaluating parameters. In coagulation–flocculation process using single coagulant, coagulant dosage and pH play an important role in determining the coagulation efficiency. At the optimum alum dosage of 1000 mg/L and optimum pH of 6.0, turbidity reduction is found to be 99.8%, TSS removal is 99.4% and COD reduction is 91%. The optimum dosage and pH for PACl are 500 mg/L and 6.0, respectively, at which it gives 99.9% reduction of turbidity, 99.5% of TSS removal and 91.3% of COD reduction. A combination of inorganic coagulant and flocculant or polymer is applied in which alum and PACl are used coupled with the C-PAM (Organopol 5415) and A-PAM (Chemfloc 430A). Overall, alum coupled with Organopol 5415 is the best system among all systems studied. It gives 99.7% reduction of turbidity, 99.5% removal of TSS and 95.6% reduction of COD, and at the same time with low SVI (38 mL/g) and low settling time (12 s).

DBPs formation and toxicity monitoring in different origin water treated by ozone and alum/PAC coagulation

In this study, aluminium sulphate (alum) and polyaluminum chloride (PAC) coagulation were used for coagulation of different origin water (Buyukcekmece, BC and Omerli, OM in Istanbul, Turkey and Carmine, CR in Salerno, Italy) treatment. The effect of pre-ozonation alone and combined with coagulation on NOM removal which was characterized by TOC, UV254 was investigated. DBPs formation and acute toxicity on Daphnia magna of chlorinated raw and treated samples were defined in parallel. Moreover, bromide spiking was evaluated for DBPs speciation. Optimum alum dose for TOC removal was found to be 40 mg/L for OM while 80 mg/L of alum exhibited the lowest total trihalomethane formation potential (TTHMFP). Pre-ozonation enhanced the removal of TOC and reduction of TTHMFP when it was used in combination with both coagulants. In contrast, total haloacetic acid formation potential (THAAFP) increased after each coagulation, ozonation and their combination. 300 µg/L bromide spiking (around the same level with BC) in raw sample collected from CR increased the formation of brominated disinfection byproducts. Raw and treated samples displayed acute toxicity on Daphnia magna in different pattern and practically “no dose-response behavior” was observed.

Nanoparticles in wastewater from a science-based industrial park—Coagulation using polyaluminum chloride

The Hsinchu Science-based Industrial Park (HSIP) is the hi-tech manufacturing hub of Taiwan. Wastewater from the HSIP contains numerous nano-sized silicate particles whose size distributions peak at 2 and 90 nm. A 3–5 mg l −1 as Al dose of polyaluminum chloride (PACl) was used in the field to coagulate these particles, but the removal efficiency was low. Laboratory scale tests indicated that although PACl coagulation removed 52% of the turbidity and 48% of the chemical oxygen demand (COD) from water, its effect on nano-particle removal was minimal. About 58% of the soluble COD was associated with colloidal Si particles. A light scattering test and transmission electron microscopy (TEM) demonstrated that the nano-particles agglomerated in approximately linear aggregates of sizes 100–300 nm. Prolonged contact between residual PACl and the nano-particles generated large aggregates with sizes of up to 10 μm and a fractal dimension of 2.24–2.63. The results presented herein should be of interest in the processing of “high-tech” wastewater that contains nanosized silica particles.