Polyaluminum Chloride Dosage Research Articles

Impact of Al-based coagulants on the formation of aerobic granules: Comparison between poly aluminum chloride (PAC) and aluminum sulfate (AS)

As widely used Al-based coagulants, poly aluminum chloride (PAC) and aluminum sulfate (AS) were adopted in a short term at the start-up stage (from 10th to 16th) to enhance the formation of aerobic granules, and their effects on aerobic granulation were elucidated. The results suggested that both PAC and AS facilitated the granulation by improving the physicochemical properties of sludge. The reactor performance in pollutant removal was also enhanced. Specifically, in terms of extracellular polymeric substances (EPS), PAC dosing mainly stimulated the production of loosely bound EPS (LB-EPS), whereas more tightly bound EPS (TB-EPS) were secreted with the presence of AS. Based on the elemental analysis, polymeric Al hydrolyzed from PAC mainly worked on the exterior of microbial aggregates, and thus the attached aluminum in granules was gradually eliminated by ion exchange and hydraulic shear force. In contrast, the aluminum species in AS hydrolyzed into monomeric and oligomeric Al, and thus could diffuse into the interior of microbial aggregates and eventually created an “Al-core” in the granules. Overall, the present study describes the AGS formation with Al-based coagulants and the mechanisms of PAC- and AS-enhanced aerobic granulation.

Membrane fouling in a hybrid process of enhanced coagulation at high coagulant dosage and cross-flow ultrafiltration for deinking wastewater tertiary treatment

A hybrid process of enhanced coagulation at a high dosage of polyaluminum chloride and flat-sheet cross-flow ultrafiltration was used for the advanced treatment of the effluent from a biological treatment process of deinking wastewater in a paper mill. The experimental results obtained by a small-scale continuous laboratory experimental device showed that the absorption resistance was significantly lower than the membrane intrinsic resistance, the concentration polarization resistance, the pore blocking resistance, and the cake layer resistance and so it can be ignored. With increasing polyaluminum chloride dosage from 0 to 2,000 mgL-1, the total membrane filtration resistance decreased and the membrane flux increased, but the concentration polarization resistance increased. With the increase in cross flow velocity, the total membrane filtration resistance, the pore blocking resistance, the layer resistance, and the concentration polarization resistance all decreased, and consequently, the membrane flux increased. With regard to the concentration polarization resistance, the cross flow velocity had a more significant effect than the trans-membrane pressure. But the trans-membrane pressure had a more significant effect on the layer resistance, the pore blocking resistance, and the total membrane filtration resistance than the cross flow velocity. The filtration resistance at the polyaluminium chloride dosage of <1,000 mgL-1 could be ranked as follows: the membrane intrinsic resistance > the pore blocking resistance > the layer resistance > the concentration polarization resistance> the absorption resistance. But it was the membrane intrinsic resistance > the concentration polarization resistance > the pore blocking resistance > the layer resistance > the absorption resistance at the dosage of ≥1,000 mgL-1. The results are helpful for the membrane fouling control and can promote the application of flat-sheet cross-flow membrane process, resultantly improving the reclaim and reuse of deinking wastewater, and reducing the emission of contaminants in deinking wastewater.

Effect of polyaluminum chloride on coal flotation performance with different reagent addition regimes

The flotation tests of an artificial mixture of coal (250–125 μm) and kaolinite (−100 μm) were conducted with two different reagent addition regimes to improve understanding of the effect of polyaluminum chloride (PAC) on coal flotation with n-dodecane as collector. The flotation results suggested that improved separation efficiency with reduced kaolinite entrainment could be achieved by addition of PAC at a proper concentration. The kaolinite entrainment mitigation was insensitive to the sequence of addition of PAC and the collector whereas addition of the collector prior to PAC appeared to be conducive to increasing the flotation rate and alleviating the requirement for close management of PAC dosage. A real-time particle characterization tool, Focused Beam Reflectance Measurement (FBRM), was used to measure the particle size distribution of kaolinite and coal in aqueous solution. It was found that the kaolinite particles formed aggregates with PAC at 10–20 mg/L, which matched well with the optimum dosage of PAC for mitigation of kaolinite entrainment in coal flotation. The induction time measurement was conducted for the coal particles, and the results suggested that addition of PAC would decrease the probability of bubble-particle attachment.

Potential use of oil palm trunk starch as coagulant and coagulant aid in semi-aerobic landfill leachate treatment

Abstract Landfill leachate is highly polluted wastewater and generated as a result of water infiltration through solid waste produced domestically and industrially. This study investigates the potential use of oil palm trunk starch (OPTS) and crosslinks oil palm trunk starch (C-OPTS) as coagulant and coagulant aid in tandem with polyaluminum chloride (PAC) for the treatment of landfill leachate. As primary coagulant, the optimum pH and dosage for OPTC were 7 and 500 mg/L, respectively. For C-OPTS, the optimum conditions were pH 8.3 and 1,000 mg/L C-OPTS dosage. However, the optimum conditions for PAC were pH 7 and 8,000 mg/L PAC dosage. Results show that OPTS demonstrated superior feasibility as a selective coagulant targeting heavy metals such as Mn (100% removal), Cu (95.6% removal), Zn (100% removal), and PO43− (100% removal), whereas C-OPTS can be employed as both bulk and selective coagulants. On the other hand, C-OPTS prevailed over PAC in Mn, Zn, PO43−, and chemical oxygen demand (COD) removals by huge margins of 100%, 54.8%, 24.3%, and 17.1%, respectively, without any pH adjustments and with optimum dosage 87.5% lower than that of PAC.

Study on Purification Technology of High-salt Nitrogenous Printing and Dyeing Wastewater

This paper reports the microbial nitrogen removal, flocculation and decolorization purification technology of high-salt nitrogenous printing and dyeing wastewater. The combined microbial flora was used to perform simultaneous nitrification and denitrification (SND) nitrogen removal for high-salt nitrogenous printing and dyeing wastewater. When the sodium acetate was the carbon source and C:N was set to 7.5:1, the concentration of -N was reduced from the initial 2000.0 mg/L to 18.0 mg/L and the nitrogen removal rate was 99.1% and the nitrogen removal efficiency was 16.5 mg·L−1·h−1 at 120 h. Poly aluminum chloride (PAC) was the suitable flocculant. Under the optimized conditions that the dosage of PAC was 0.5 g/L and the flocculation time was 10 min, the flocculation rate reached 96.5%. Among the four decolorization methods of ozone, 84 disinfectant, hydrogen peroxide and chlorine dioxide, the decolorization effect of ozone oxidation was superior. When the production of ozone was 167 mg/min and the reaction time was 4 min, the decolorization rates all of neutral red, acid green and methyl orange could reach over 94.0%. This study provides theoretical and technical support for the purification of high-salt nitrogenous printing and dyeing wastewater.

An integrated process involved coagulation and anaerobic sequencing batch reactor (ASBR) to remove organic substances in mechanical dewatering wastewater from municipal garbage

Mechanical dewatering wastewater (MDW) from municipal garbage is a mixture that is quickly separated from raw domestic waste by high-pressure extrusion without a sump fermentation process. Alkali treatment-coagulation sedimentation-ASBR treatment technology was adopted in this study to treat SS and organic matter. The results showed that the optimum pH of the alkali treatment was 9.0, polyaluminum chloride (PAC) was the best coagulant for the coagulation and sedimentation of MDW. The optimal working condition were gotten with a Ca(OH)2 dosage of 200 mg/L, a pH of 10.0, and a PAC dosage of 800 mg/L, under the intermittent stirring mode of 250 r/min for 1 min and then 50 r/min for 10 min. Perfect domestication effect of the ASBR was achieved under medium temperature for 28 days. The optimum conditions for ASBR were determined as follows: temperature was 35 °C, and organic loading rate (OLR) was 6 kg COD/ (L·d). Analysis of the microbial community structure succession showed that the success rate of anaerobic microorganisms in medium temperature ASBR was fast and adaptable. This study provides technical support for the actual application.

Combined effect of ozone and PTFE membrane on treating shale gas produced wastewater in Fuling Shale Gas Field

Shale gas produced wastewater (SGPW) is difficult to be treated by conventional treatment processes due to its high total dissolved solids, chemical oxygen demand (COD), salinity (SAL), bacteria, and complex physicochemical composition. In this study, a new combined process of ozonation and polytetrafluoroethylene (PTFE) membrane was developed to treat SGPW in Fuling Shale Gas Field, China, for the first time. Polyaluminum chloride (PAC) was selected as flocculant for the pretreatment, and the ozonation was used to control sulfate-reducing bacteria (SRB), iron bacteria (FEB), total growth bactericide (TGB), and degrade macromolecule organic matter. The PTFE microfiltrate membrane was applied to treat COD and SAL. The results demonstrated that the removal of SRB, FEB, TGB, and COD was 55.6%, 78.6%, 77.3%, and 67.0%, respectively, with the conditions of PAC dosing quantity 400 mg/L, Ozone dosing quantity 3 g/h, and residence time 20 min. The combined process exhibited effective removal performance and is potential to be applied for treating SGPW in China.

Managing Eutrophication in a Tropical Brackish Water Lagoon: Testing Lanthanum-Modified Clay and Coagulant for Internal Load Reduction and Cyanobacteria Bloom Removal

The release of phosphorus (P) stored in the sediment may cause long-term delay in the recovery of lakes, ponds, and lagoons from eutrophication. In this paper, we tested on a laboratory scale the efficacy of the flocculant polyaluminium chloride (PAC) and a strong P-binding agent (lanthanum-modified bentonite, LMB) on their ability to flocculate a cyanobacterial bloom and hamper P release from a hypertrophic, brackish lagoon sediment. In addition, critical P loading was estimated through PCLake. We showed that cyanobacteria could be effectively settled using a PAC dose of 2 mg Al L−1 combined with 400-mg L−1 LMB; PAC 8 mg Al L−1 alone could also remove cyanobacteria, although its performance was improved adding low concentrations of LMB. The efficacy of LMB to bind P released from the sediment was tested based on potentially available sediment P. A dose of 400 g LMB m−2 significantly reduced the P release from sediment to over-standing water (either deionized water or water from the lagoon with and without cyanobacteria). In sediment cores, LMB + PAC reduced sediment P flux from 9.9 (± 3.3) to − 4.6 (± 0.3) mg P m−2 day−1 for the experimental period of 3 months. The internal P load was 14 times higher than the estimated P critical load (0.7 mg P m−2 day−1), thus even if all the external P sources would be ceased, the water quality will not improve promptly. Hence, the combined LMB + PAC treatment seems a promising in-lake intervention to diminish internal P load bellow the critical load. Such intervention is able to speed up recovery in the brackish lagoon once external loading has been tackled and at a cost of less than 5% of the estimated dredging costs.

Membrane fouling and performance of anaerobic ceramic membrane bioreactor treating phenol- and quinoline-containing wastewater: granular activated carbon vs polyaluminum chloride.

Although anaerobic membrane bioreactor (AnMBR) has been proposed for the treatment of phenolic wastewater, the membrane fouling is still a major obstacle. The effects of dosing of granular activated carbon (GAC) and polyaluminum chloride (PACl) on the treatment performance and membrane fouling of anaerobic ceramic membrane bioreactor were investigated for treating phenol- and quinoline-containing wastewater. The results suggested that the one-off dosing of GAC resulted in a decrease of protein/carbohydrate ratio, which might account for the aggravation of membrane fouling alongside with the decreased flocs size. Nevertheless, the substrate uptake rates (SUR) of phenol and quinoline, and the specific methanogenic activity of sludge at the GAC dosing stage of experimental reactor (R1) were 8.79 ± 0.63mg phenol g-1 MLVSS d-1, 7.01 ± 0.09mg quinoline g-1 MLVSS d-1 and 0.27 ± 0.01g CODCH4 g-1 MLVSS d-1, which were 1.69, 3.59 and 1.93 times higher than that of the control reactor (R2). The dosing of PACl reduced the membrane fouling rate by changing the floc structure of sludge, as well as the component of SMP and EPS. However, the substrate uptake rate of quinoline was declined. This work provides a comprehensive evaluation on the effect of GAC and PACl dosing on membrane fouling and performance of anaerobic ceramic membrane bioreactor treating phenol-and quinoline-containing wastewater.

Potential Use of Dimocarpus longan Seeds as a Flocculant in Landfill Leachate Treatment

Landfill leachate is a highly polluted and generated from water infiltration through solid waste produced domestically and industrially. In this study, a coagulation–flocculation process using a combination of Polyaluminium chloride (PACl) as a coagulant and Dimocarpus longan seed powder (LSP) as coagulant aid was used in treating landfill leachate. LSP has been tested as the main coagulant and as coagulant aid with PACl. As the main coagulant, the optimum dosage and pH for PACl were 5 g/L and 6, respectively, with removal efficiencies of 67.44%, 99.47%, and 98% for COD, SS, and color, respectively. For LSP as the main coagulant, results show that LSP is not effective where the removal efficiencies obtained for COD, SS, and color were 39.40%, 22.20%, and 28.30%, respectively, with the optimum dosage of 2 g/L and pH 4. The maximum removal efficiencies of COD, SS, and color were 69.19%, 99.50%, and 98.80%, respectively, when LSP was used as coagulant aid with PACl. Results show that using LSP as coagulant aid was found to be more effective in the removal of COD, SS, and color with less PACl dosage. The PACl dosage was decreased from 5 to 2.75 g/L when LSP was used as a coagulant aid. Cost estimation for using PACl alone and using LSP as the coagulant aid showed a reduction in the cost of approximately 40% of the cost of using PACl alone. Overall, this study confirmed the efficiency of LSP to be used as a natural coagulant aid in leachate treatment.

Enhanced coagulation process by Fe-Mn bimetal nano-oxides in combination with inorganic polymer coagulants for improving As(V) removal from contaminated water

This study investigated the efficient removal of As(V) from contaminated water using enhanced coagulation by Fe-Mn bimetal nano-oxides in combination with poly-ferric chloride (PFC) and poly-aluminum chloride (PAC). The effects of coagulant dose, initial pH, initial As(V) concentration, Fe-Mn nano-oxide dose and flocs properties were investigated. The results showed that the combination of coagulants and nano-oxides significantly increased the As(V) removal efficiency in the optimal coagulants doses (25 mg/L). The As(V) removal efficiencies for PAC and PFC were 82.93% and 88.22% and for PFC + Fe-Mn and PAC + Fe-Mn were increased to 96.83% and 98.26%, respectively. The residual As(V) concentration was decreased to ˂10 μg/L in the presence of Fe-Mn nano-oxides. The best removal efficiencies for PAC + Fe-Mn and PFC + Fe-Mn were in pH 7 and 9, respectively. Based on FESEM - EDX analysis, the combined floc formation by coagulants - nano-oxides and the existence of Fe, Mn and As elements in the precipitated flocs was confirmed, and the PFC + Fe-Mn flocs were more uniform and bigger than PAC + Fe-Mn flocs. Total Fe and Al residual concentrations in optimum dose of PAC + Fe-Mn and PFC + Fe-Mn were 0.15 and 0.25 mg/L and Cl− residue concentrations were 6.87 and 4.72 mg/L, respectively. Therefore, the combination of Fe-Mn bimetal nano-oxides with PFC and PAC coagulants can be a suitable option to improve the removal of As(V) from the contaminated water resources.

Synergistic strengthening mechanism of hydraulic selection pressure and poly aluminum chloride (PAC) regulation on the aerobic sludge granulation

This study aimed to enhance aerobic granulation by the integration of hydraulic selection pressure (HSP) and poly aluminum chloride (PAC) regulation. Based on an investigation of sludge characteristics, microbial aggregation and extracellular polymeric substances (EPS) secretion, the synergistic mechanisms of HSP and PAC regulation were revealed. For granule formation, HSP primarily improved the cell hydrophobicity and extracellular protein production, while PAC regulation markedly neutralized the surface charge of cells and reduced the interaction energy between them. In addition, biomass retention was also facilitated by the PAC dosing. Notably, the results of total interaction energy and flocculating ability imply that prior HSP screening could significantly promote PAC regulation on microbial aggregation. To optimize the balance between granule formation and reactor performances, five kinds of integrated strategies for HSP and PAC regulation were conducted in batch test. According to the results, 4.3 g/L initial mixed liquor volatile suspended solids (MLVSS) was preferred before the addition of PAC.

Perbandingan Kebutuhan Koagulan Al2(So4)3 dan PAC Untuk Pengolahan Air Bersih Di WTP Sungai Ciapus Kampus IPB Dramaga

Water Treatment Plant (WTP) IPB process water from Ciapus River by water purifying process before distributed to consumers. The type of coagulant used is Al2(SO4)3 (aluminum sulfate) or alum and Polyaluminium Chloride (PAC). This study aimed to compare the water quality by using coagulant Al2(SO4)3 and PAC in WTP Ciapus River IPB Dramaga and to find out the optimum dosage of coagulant alum and PAC . This study used a test jar method and ISO (SNI) for the analysis of physical and chemical parameters of water. Based on the results of research, PAC was better than alum with the optimum dose of 20 ppm which produces 0.22 NTU of turbidity, 1 mg/l of TSS and 150 mg/l of TDS. While the optimum dose of alum was 20 ppm which generates 0.49 NTU of turbidity, 0 mg/l of TSS and 164 mg/l of TDS. Average costs for the use of coagulant alum and PAC were Rp. 95/m3 and Rp 215/m3, while the average value of the efficient used of coagulant alum and PAC were 91.34% and 83%. The results of both coagulants meets the criteria of water quality standards in accordance with Regulation of the Minister of Health No. 429 of 2010.

Reducing quartz entrainment in fine coal flotation by polyaluminum chloride

Flotation tests using artificial mixtures of clean coal and quartz were conducted with and without the presence of sodium hexametaphosphate (SHMP) to study the effect of polyaluminum chloride (PAC) on quartz entrainment in fine coal flotation. Comparisons of flotation results show that the degree of quartz entrainment was greatly reduced using a suitable amount (e.g., 20 mg/L) of PAC in the absence of SHMP, however, significant changes of PAC on quartz entrainment did not appear in the presence of SHMP. The possible mechanisms responsible for the reduced quartz entrainment using PAC in fine coal flotation were investigated by particle size distribution measurements, zeta potential measurements, and interaction force calculations. Analysis of particle size distribution results reveals that when SHMP was not added, quartz particles were selectively aggregated with the addition of 20 mg/L PAC and the aggregation of quartz or coal particles was negligible at a high PAC dosage (e.g., 50 mg/L). Meanwhile, the aggregation of quartz particles induced by PAC was eliminated with the presence of SHMP. The electrostatic double layer repulsive force between quartz particles was calculated using the Deyaguin-Landau-Verwey-Overbeek (DLVO) theory with incorporating the results of zeta potential measurements. At 20 mg/L of PAC, the negative surface charge of quartz particle was neutralized and the electrostatic double layer repulsive force between quartz particles reached the minimum. These findings might be reasons of the aggregation of quart particles and therefore reduce the quartz entrainment in fine coal flotation.

Determining the effects of polyaluminum chloride alkalinities and dosage treatments on various microalgal growth phases for the treatment of microalgae-laden water

Harmful algal blooms have become critical threats to human health as they have occurred with increasing frequency and intensity in various water bodies. In the People’s Republic of China, thousands of people are exposed to water bodies heavily contaminated with microalga Microcystis aeruginosa and thus at grave risk of microcystin poisoning. This study investigated the characteristics of extracellular organic matters (EOMs), floc morphology, and microcystin in each microalgal growth phase for the treatment of microalgae-laden water. The characterization was performed under different alkalinities and dosage treatments of polyaluminum chloride (PAC). Results suggested fulvic-like and humic-like acids, CC, and unsaturated aldehyde ketones were present in the supernatant liquor and dissolved EOM (dEOM) solution under logarithmic and stationary phase treatments for EOM. However, the same components along with aromatic protein and amidogen were detected in the supernatant liquor and dEOM solution under the decline phase treatments. The EOM of the supernatant liquor and dEOM solution nearly resembled willmigerl, which was different from bound extracellular organic matter (bEOM) in the three growth phases. Nonetheless, the highest particle size and most compact and roughest flocs were observed in the stationary phase. Meanwhile, no significant difference (P > 0.05) was observed among the microcystin concentrations of microalgal cells before and after coagulation, although the concentrations increased after the coagulating treatment. Therefore, coagulation pH of 2.0 and 50 mg L−1 dose of PAC was a good practical application to treat microalgae laden water at the stationary growth phase.

Broadening of appropriate demulsifier dosage range for latex-containing wastewater by sulfate addition

Investigation of demulsification of polybutadiene latex (PBL) wastewater by polyaluminum chloride (PAC) indicated that there was an appropriate dosage range for latex removal. The demulsification mechanism of PAC was adsorption-charge neutralization and its appropriate dosage range was controlled by zeta potential. When the zeta potential of the mixture was between -15 and 15 mV after adding PAC, the demulsification effect was good. Decreasing the latex concentration in chemical oxygen demand (COD) from 8.0 g/L to 0.2 g/L made the appropriate PAC dosage range narrower and caused the maximum latex removal efficiency to decrease from 95% to 37%. Therefore, more accurate PAC dosage control is required. Moreover, adding 50 mg/L sulfate broadened the appropriate PAC dosage range, resulting in an increase in maximum latex removal efficiency from 37% to 91% for wastewater of 0.2 g COD/L. The addition of sulfate will favor more flexible PAC dosage control in demulsification of PBL wastewater.

Floc Performance parameters during water treatment in a micro-vortex flocculation process determined by machine vision

ABSTRACTThe coagulant dosage of an existing water plant is mainly determined based on the experience of water treatment process and influent/effluent water quality indexes that have time hysteresis effects. To solve this problem, the effect of coagulant dosage on a number of parameters used to evaluate the efficiency of flocculation in a setup was determined by using the micro-vortex flocculation technology in conjunction with the investigation of the relation between the equivalent diameter and the fractal dimension. By means of the machine vision system and computerized analysis, the effects of floc quantity, floc equivalent diameter and fractal dimension can be assessed. The correlations of these parameters with turbidity and ζ potential of the settling water, taken as measures for effluent quality, were explored. The study results show that the optimal flocculation effect with a turbidity removal rate of 97.9% is achieved at the poly-aluminum chloride dosage of 20 mg/L. Meanwhile, a power exponential relation between the floc equivalent diameter and the fractal dimension was established with a correlation coefficient R2 of 0.826; relations among the effluent turbidity and the floc quantity, equivalent diameter, fractal dimension were established with a correlation coefficient R2 of 0.982, 0.851, and 0.875, respectively; equations between the ζ potential and the floc quantity, equivalent diameter, fractal dimension were also established where the correlation coefficient R2 were 0.868, 0.879, and 0.942, respectively. These results may provide excellent reference data for water plants to feed back the coagulant by floc performance parameters, which could relieve the hysteresis effect efficiently.

Restoration of a eutrophic hard-water lake by applying an optimised dosage of poly-aluminium chloride (PAC)

Feldberger Haussee (NE Germany) was polluted for almost a century. During the late 1970s, the nutrient input reached a maximum of approximately 1.9/11.5 g TP/TN m−2 yr−1. As a result, the lake became a hypertrophic ecosystem and had largely lost its recreational value. In 1980, the sewage discharge was stopped, decreasing the external loading by approximately 90%. Because of vast amounts of phosphorus stored in the sediment, the lake remained highly eutrophic until 1985 with a TP concentration of ca. 1 mg L−1. To accelerate recovery, biomanipulation was applied from 1985 to 2002 but was successful to only a minor extent. Eventually, due to sediment sequestration and discharge to downstream lakes the TP spring maximum (2006–2010) dropped to 0.112–0.078 mg L−1. However, given the trend, it was obvious that it would take another 10–15 years for the concentration to approach the desired mesotrophic level. Thus, it was suggested to inactivate the surplus phosphorus by treating the lake with poly-aluminium chloride (PAC) as precipitant. To ensure good water quality, the objective was to decrease concentrations below 0.035 mg TP L−1, while optimising the amount of PAC applied (as much as needed, but as little as possible). As a prerequisite, the status of the lake was carefully studied; external phosphorus loading and the amount of mobile phosphorus stored in the sediment being of specific interest. Laboratory experiments, modelling studies and field observations eventually resulted in an estimated dosage of 27 g Al m−2 (molar Al/P 12). Following the treatment in April 2011, prime water quality parameters showed two opposing trends: (1) TP concentration immediately dropped below the restoration target (≤0.025/0.035 mg L−1), primary production and phytoplankton biomass declined substantially. (2) However, water clarity did not improve for another four years. The likely reason for the delay was the structure of the phytoplankton community. It was dominated by cyanobacteria with the potential to trigger intensive calcite precipitation and thus impair transparency. In spring 2015, the cyanobacteria suddenly disappeared and transparency increased significantly. We speculate that these changes of the planktonic community shifted the ratio of assimilation and respiration in favour of the latter. This allowed an increase of free CO2* (dissolved CO2 & dissociated carbonic acid) altering the carbonate buffering system and thus halting the formation of calcite crystals. Also, the phytoplankton, now represented by small readily ingestible taxa, promoted a flourishing Daphnia population inflicting heavy grazing losses, resulting in clear water stages (2015 June, 4.20 m; 2016, August 3.70 m; 2017 August, 4.5 m). We conclude that the drastic decrease of phosphorus availability in concert with structural and functional changes of the plankton community eventually improved the water quality of Haussee significantly. The lake is now in a mesotrophic status; well in accordance with the aim of the restoration project.

Effects of polyaluminum chloride and lanthanum-modified bentonite on the growth rates of three Cylindrospermopsis raciborskii strains

In tropical and subtropical lakes, eutrophication often leads to nuisance blooms of Cylindrospermopsis raciborskii. In laboratory experiments, we tested the combined effects of flocculant polyaluminum chloride (PAC) and lanthanum-modified bentonite (LMB) on the sinking and growth rates of three C. raciborskii strains. We tested the hypothesis that the combination of PAC and LMB would (1) effectively sink C. raciborskii in a test tube experiment and (2) impair C. raciborskii growth, irrespective of the biomass of the inoculum (bloom) and the strain in the growth experiment. We tested the recommended (LMB1) and a three-times higher dose of LMB (LMB3). The combined addition of PAC and LMB enhanced the sedimentation of all C. raciborskii strains. Moreover, both the PAC and LMB doses decreased the phosphate concentration. PAC and LMB1 decreased the growth rate of all strains, but the efficacy depended on the biomass and strain. The combined addition of PAC and LMB3 inhibited the growth of all strains independently of the biomass and strain. We conclude that a low dose of PAC in combination with the recommended dose of LMB decreases C. raciborskii blooms and that the efficiency of the technique depends on the biomass of the bloom. A higher dose of LMB is needed to obtain a more efficient control of C. raciborskii blooms.

Dissolved Air Flotation for Fiber Removal from Clear Water

ABSTRACT We investigated the use of dissolved air flotation (DAF) to treat clear water effluent from the paper industry in order to remove fibers. The dosage of polyaluminium chloride (PAC) was varied in the following concentrations: 0, 75, 100, 125, 150 and 175 mg/L; as well as bubble rise velocity of 18 and 9 cm/min for two types of paper wastewater: print and gloss. Data were statistically analyzed through factorial arrangement 6x2x2. The treatment of the print paper effluent showed better performance in removing the analyzed parameters with an optimal dosage of 100 mg/L PAC, whereas the gloss paper effluent treatment had satisfactory removal of analyzed parameters with an optimal dosage of 150 mg/L of PAC. This led to the observation that the high efficiency directly obtained with the DAF in conjunction with the use of PAC coagulant was an excellent primary treatment option for effluent resulting from the paper industry.