Addition Of Polyaluminum Chloride Research Articles

Experimental investigation of the inhibition of deep-sea mining sediment plumes by polyaluminum chloride

Deep-sea sediment disturbance may occur when collecting polymetallic nodules, resulting in the creation of plumes that could have a negative impact on the ecological environment. This study aims to investigate the potential solution of using polyaluminum chloride (PAC) in the water jet. The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area. The experimental results showed that the optimal PAC dose was found to be 0.75 g/L. Compared with the test conditions without the addition of PAC, the presence of PAC leads to a reduction in volume, lower characteristic turbidity, smaller diffusion velocity, and shorter settling time of the plume. This indicates that PAC inhibits the entire development process of the plume. The addition of PAC leads to the flocculation of mm-sized particles, resulting in the formation of cm-sized flocs. The flocculation of particles decreases the rate of erosion on the seabed by around 30%. This reduction in erosion helps to decrease the formation of plumes. Additionally, when the size of suspended particles increases, it reduces the scale at which they diffuse. Furthermore, the settling velocity of flocs (around 10−2 m/s) is much higher that of compared to sediment particles (around 10−5 m/s), which effectively reduces the amount of time the plume remains in suspension.

Removal of Nano-Zinc Oxide (nZnO) from Simulated Waters by C/F/S—Focusing on the Role of Synthetic Coating, Organic Ligand, and Solution Chemistry

Increased usage of nano-zinc oxide (nZnO) in different commercial fields has raised serious concerns regarding their discharge into the water streams containing natural and synthetic coating agents. Moreover, utilization of ground and surface water for drinking purposes is a common approach in many countries. Therefore, the removal of nZnO particles from water is essential to minimize the risk to the environment. The present research investigated the removal of nZnO from complex water matrices by conventional coagulation-flocculation-sedimentation (C/F/S) process using polyaluminum chloride (PACl) as coagulants. The result showed that removal of uncoated nZnO through sedimentation was efficient in waters containing divalent cations in the absence of dissolved organic matter (DOM). For the water containing higher salt concentration, PACl coagulant showed better removal performance with increasing coagulant dosage; however, synthetic organic coating agent and DOM significantly decreased the removal up to 75%. The surface potential of studied waters indicated that the addition of PACl affects the charge potential of nZnO particles resulting in charge neutralization. The result of the particle size analyzer revealed the presence of smaller particles with size of 430 nm even after C/F/S process, which may increase the possibility of particles release into aquatic environment. The results of the present study may help in understating the removal behavior of other coated nanoparticles during conventional water treatment.

Effects of different chemical agents on changes in sediment phosphorus composition and the response of sediment microbial community

Controlling the release of sediment phosphorus (P) using chemical agents is a promising method for controlling internal P in eutrophic lakes. However, mineral P formation and changes in the organic P composition after sediment amendment with P-inactivation agents remain poorly understood. Furthermore, little is known about the changes in the sediment microbial community composition after remediation. Here, various ratios of poly aluminum chloride (PAC) and lanthanum-modified bentonite (LMB) were added to nutrient-rich sediments and incubated. Sequential P extraction, solution/solid-state 31P nuclear magnetic resonance (NMR), and microbial analyses were periodically performed on the inactivated sediments. The results indicate that PAC and LMB effectively reduced sediment iron-bound P and organic P, respectively, markedly increasing the content of aluminum- and calcium-bound P in the sediment, respectively. Solid-state 31P NMR results confirmed the formation of rhabdophane (LaPO4. nH2O) in the LMB-amended sediment. Solution 31P NMR results showed that PAC preferentially reduced the organic P fractions of pyrophosphate, whereas LMB efficiently reduced the organic P fractions of orthophosphate, monoesters, and diesters in the sediment. Compared with the control sediment, PAC addition can cause short-term negative effects on sediment microbes at high doses, whereas LMB addition can increase bacterial diversity or richness in the sediment. These results provide a deeper understanding of the differences between PAC and LMB in internal sediment P control.

Investigation of coagulation and microfiltration for Danube water as the first step of make-up water production

A comparison of coagulation with two coagulants, poly-aluminum chloride (PACl) and ferric chloride (FeCl3), followed by microfiltration, was evaluated to obtain a better coagulant for an efficient pretreatment method for make-up water preparation from Danube water for thermal power plants. Efficiency was determined by chloride concentration and retention based on the total suspended solid content of the treated water samples. Results were compared to microfiltration working alone as a chemical-free pretreatment. Addition of PACl resulted in the lowest total suspended solid content (18.0 ± 1.3 mg/L), slightly lower than obtained for microfiltration alone (19.6 ± 2.5 mg/L) and significantly lower than for FeCl3 (25.0 ± 3.3 mg/L). Regarding the retention values, coagulation with PACl followed by microfiltration, microfiltration working alone and coagulation with FeCl3 followed by microfiltration represented retention values of 68%, 66.21%, and 56.89%, respectively. Considering the chloride concentration, it remained constant after microfiltration alone; meanwhile, adding coagulants showed a significant rise, ~ 6.4- and 5.7-times higher than the raw water's value after adding FeCl3 and PACl, respectively. From environmental viewpoint, microfiltration alone is recommended because it can provide a steady flux and low total suspended solid content without additional load of chloride ion which shall be eliminated in the further desalination step.

Anti-fouling performance and methane potential in coagulation-adsorption assisted biogas-spared anaerobic membrane preconcentration process

To preconcentrate domestic sewage and control membrane fouling, this study proposed a novel anaerobic membrane-based preconcentration (AnMPC) system and controlled fouling by coagulation-adsorption assisted biogas sparging. The effect of polyaluminium chloride (PACl) dosage on membrane fouling control and methane potential of preconcentrated domestic sewage was also investigated. Membrane fouling control was realized by the increase of particle-size (6.03%–40.65%) and the decline of soluble microbial product (11.10%–33.14%) with the rise of PACl addition. The minimum membrane filtration resistance of 1.15 × 1013 m−1 was obtained at the group with 10 mg/L PACl, which was 7.96%–28.20% lower than other groups. More than 75% of chemical oxygen demand (COD) could be preconcentrated, and the preconcentrated ratio increased by 4.22%–9.70% with the rise of PACl addition. Methane potential decreased by 5.40%–40.56% due to the inhibition of accumulated PACl. The pre-hydrolysis of domestic sewage during AnMPC could shorten fermentation time by 0.8–3.2 d. The group with 10 mg/L PACl addition was the optimal due to the excellent anti-fouling performance and the promising energy balance. This study could provide a promising membrane-based preconcentration method with high COD recovery and mild membrane fouling for sustainable treatment of domestic sewage.

Reduction of TSS, COD, Oil and Fat in Palm Oil Mill Waste Using Dissolved Air Flotation Method

This study aims to determine the effect of variations in pressure and contact time of wastewater with air to decrease the parameters of TSS, COD, and oils and fats contained in palm oil wastewater. This study uses a series of Dissolved Air Flotation (DAF) process units with the addition of Poly Aluminum Chloride (PAC) coagulant. This research begins with the manufacture of a series of DAF tanks and flotation tanks. Waste flow is carried out in batches and the air is flowed upflow through the bottom hole of the DAF tank. The pressure variables used in decreasing the parameters of TSS, COD, and oil and fat are absolute 2; absolute 2.5; and absolute 3 atm. The contact time variables for decreasing TSS, COD, and oil and fat parameters were 15, 30, 45, 60, and 75 minutes. The results showed a decrease in each of the tested parameters. The effective pressure to reduce the value of the TSS parameter is the absolute pressure of 3 atm and the absolute pressure of oil and grease is 2.5 atm. While the effective pressure to reduce the value of the COD parameter is an absolute pressure of 3 atm. The best contact time between air and wastewater to set aside the values of the TSS, COD, and oil-fat parameters was 75 minutes.

Poly Aluminum Chloride (PAC) as Coagulant in Liquid Waste Treatment of Tofu

The tofu craftsmen have not processed the liquid waste produced and disposed of the liquid waste directly into the waters as a result, the water quality has decreased. Tofu liquid waste has BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), and TSS (Total Suspended Solid) exceeding the permitted quality standards. Treatment of tofu liquid waste needs to be done before being disposed of, one of which is by using coagulant. The purpose of this research is to know the value of BOD, COD, TSS, and pH of tofu liquid waste before and after the addition of PAC. The study was conducted by varying the concentration of PAC (10 mg/L, 30 mg/L, and 75 mg/L). The test results show that the tofu liquid waste has a BOD value of 3,890 mg/L, COD 9558.7 mg/L, TSS 2,905 mg/L, and a pH of 3.7. The use of PAC as a coagulant reduced the values of BOD, COD, TSS, and pH. PAC concentration of 75 mg/L can reduce BOD, COD, TSS, and pH values to 3,015 mg/L, 6,900 mg/L, 840 mg/L, and 3.59, respectively.

Effect of coagulation on microfibers in laundry wastewater

Microplastics pollution in the aquatic system has received significant attention due to their recalcitrant nature and ecotoxicological threat. Municipal wastewater typically contains various microplastics with synthetic microfibers as a significant constituent from the laundry process. The fate of microfibers in conventional wastewater processes is not clearly understood. In this study, the effect of coagulation on microfibers obtained from a lint screen of a domestic dryer and resuspended in pure water, and also in laundry wastewater was investigated using ferric chloride and polyaluminum chloride (PACl). The removal efficiency of the microfibers resuspended in pure water varied from 86% to 96% depending on the fiber size ranges: < 90 μm, 90–125 μm, and >125 μm with the smaller size microfibers showing a lower removal efficiency. Surfactant present in detergent in laundry wastewater reduced the microfibers removal efficiency to 0–37%, however, the addition of PACl increased microfibers removal to 90%. The optimal PACl concentrations for ≥90% removal were 1.75, 2, 4, and 6 mg/L for 0.5, 2, 4, 8 mg/L detergent, respectively. Zeta potential, FTIR, and SEM analysis were applied to observe the surface changes of microfibers during coagulation indicating possible mechanisms of coagulation. The dominant mechanisms for coagulation of microfibers by FeCl3 and PACl seem to be charge neutralization and adsorption-bridging. This work provided some insights about the fate of laundry microfibers in primary treatment processes.

Synergistic denitrification and phosphorus removal performance of a biofilm-microflocculation system and its microbial community variations: A pilot-scale study for a wastewater treatment plant.

For upgrading and reconstructing a municipal wastewater treatment plant, a biofilm-microflocculation filter system was designed and established towards synergistic improvement of denitrification and phosphorus removal from the secondary effluent. The establishment of the biofilm-microflocculation filter system underwent several processes, including sludge inoculation, biofilm formation and polyaluminum chloride (PAC) addition as flocculating agent. Microbial community analysis indicated that the dominant denitrification bacteria of the biofilm filter were in the phylum Proteobacteria and the genera Hydrogenophaga and Dechloromonas. On the basis of the initiation of filter system under optimal parameters such as C/N ratio of 5.3, hydraulic retention time of 1.06h and PAC of 5mgL-1 , approximately 75% COD, 80% TN and 75% TP could be effectively removed to satisfy discharge standards. Comparing the variations of microbial community structure at the genus level during the operating period of the filter system, it was found that the relative abundance of denitrification bacteria merely shifted from 53.14% to 48.76%, demonstrating that the effect of PAC addition on the main micro-organisms is marginal. From the above results, it can be verified that the established biofilm-microflocculation filter system has practical and reliable performance for simultaneous biological denitrification and phosphorus removal. This study provides a reference method for improving the advanced treatment of wastewater plant secondary effluent.

Effect of different flocculants on the characteristics of hydrochar and hydroliquid derived from the hydrothermal treated active sludge. A comparative study

In this study, the effect of flocculants on the physicochemical properties of hydrochar and hydroliquid derived from hydrothermal carbonization (HTC) treated sewage sludge (SS) was investigated. The results suggested that the flocculants including polyacrylamides (PAM), polyaluminium chloride (PAC) and FeCl3 can be transferred from the liquid to hydrochar during the HTC treatment process. The PAM monomers produced from thermal degradation can be absorbed on hydrochar. The Al3+ and Fe3+ in hydrochars were in the form of oxides, hydroxides or salts. The transformation of N, S and P during HTC can be affected by the flocculants, and the thermochemical properties of the derived hydrochars exhibited obvious difference. The influence mechanisms on elements transformation can be attributed to phosphate precipitation by metal ions, pH change caused by flocculants hydrolysis and catalysis of the ions. The thermal release of hydrocarbon and N/S containing gases from the three kinds of hydrochars with PAM, PAC and FeCl3 addition demonstrated significant differences. The hydrocarbon released from hydrochar with PAC addition was much lower than the other groups, while the hydrochar with FeCl3 addition exhibited improved S containing gases release. In addition, the water quality parameter, especially total phosphorus (TP) concentration was affected by flocculants. Phosphorus can be enriched in hydrochar by PAC with 95.1% of TP kept in hydrochar. The volatile organics including fatty acids, alkanes, ketones, aldehydes, amides and pyrazines in the liquid phase were also affected by flocculants. The obtained results in this study will provide valuable information for SS utilization by HTC treatment.

Enhanced coagulation treatment of surface water benefits from Enteromorpha prolifera

Enteromorpha prolifera polysaccharide (EP) was extracted under different preparation conditions and then used in conjunction with polyaluminum chloride (PAC) or ferric chloride (FeCl3) for surface water treatment. The coagulation behavior of PAC-EP was investigated under different coagulant dosages, reaction temperatures and solution pH values. Statistical analysis was conducted to explore the main factors affecting the coagulation performance of PAC-EP. In addition, the floc structure was characterized to determine the underlying flocculation mechanism of EP in the water treatment process. The results showed that EP was a water-soluble sulfated polysaccharide with a maximum extraction rate of 15%. Compared with FeCl3, PAC exhibited a better cooperation effect with EP, and the coagulation efficiency could be enhanced by 20%−40% under a moderate dosage of EP 30 s after PAC addition. Moreover, the coagulation performance of the PAC-EP treatment was maintained at a high level over relatively wide pH (6.0–9.0) and temperature ranges (5–20 ℃). The statistical results indicated that the EP dosage was the main factor affecting the removal of organic substances. For water obtained from the Kui River, the optimal PAC-EP dosage was 1–4 mg/L, which adequately removed protein-like and humic acid-like organic substances. The aid mechanism of EP was attributed to the bridging effect of its long-chain molecular structure, which could connect PAC hydrolysates and colloidal particles effectively to form complex compounds, thus facilitating the formation of large flocs.

Selective aggregation of fine quartz by polyaluminum chloride to mitigate its entrainment during fine and ultrafine mineral flotation

• Polyaluminum chloride (PAC) could lower quartz entrainment in galena flotation. • Adding xanthate before PAC suppressed the depressive effect of PAC on galena. • PAC selectively aggregated fine quartz particles in the galena-quartz mixture. • The rate of PAC adsorption onto quartz surfaces was higher than on galena. • PAC adsorbed on quartz through both charge neutralization and Al bridging. Fine and ultrafine hydrophilic particles are typically left in a dispersed state in a flotation pulp when novel fine mineral flotation technologies are developed. These dispersed fine and ultrafine gangue particles can enter flotation concentrate by mechanical entrainment, lowering concentrate grade. The problem is becoming increasingly more pervasive as the required liberation size of value minerals in ores decreases. In this work, polyaluminum chloride (PAC) was investigated to study its effect on the reduction of quartz entrainment in the batch flotation of synthetic mixtures of quartz and galena. Apart from the evaluation of quartz entrainment, micro-flotation of galena, batch flotation of artificial mixtures of galena and quartz, the aggregation/dispersion behaviors of quartz and galena and their mixtures in the presence of PAC were studied by sedimentation, turbidity, focused beam reflectance measurement (FRBM) coupled with optical microscope observations and scanning electron microscope (SEM), and zeta potential measurements. The results indicated that the addition of PAC reduced quartz entrainment without adversely affecting galena flotation, so that the flotation separation efficiency was increased from 74% (without PAC) to 77% (when PAC was added prior to xanthate) and 80% (when xanthate was added prior to PAC) at PAC concentrations below 150 mg/L. PAC was found to aggregate the fine quartz but not galena. It was observed that PAC preferentially adsorbed on quartz in the quartz-galena mixtures, so that it lowered the entrainment of quartz and improved separation efficiency.

Effect of coagulation treatment on antifouling properties of PVC nanocomposite membrane in a submerged membrane system for water treatment

A submerged membrane system was used in this work to investigate the effect of the polyaluminum chloride (PAC) coagulant on the antifouling performance of the polyvinyl chloride/alumina (PVC/Al2O3) nanocomposite membrane. The prepared nanocomposite membranes were characterized with field emission scanning electron microscopy (FE-SEM), atomic force microscopy, contact angle, porosity measurement, and pure water flux. The results revealed that the membrane containing Al2O3 nanoparticles (the mass ratio of PVC to Al2O3 was 98.5/1.5) had a higher hydrophilicity, porosity, and pure water flux than other membranes. The FE-SEM images showed that when Al2O3 nanoparticles were present in the PVC membrane, large pores and macrovoids formed on the surface and cross-section of the membrane. The fouling behavior of membranes was investigated through the filtration of humic acid (HA) solution with and without the PAC coagulant. Without PAC addition, the PVC/Al2O3 membrane significantly decreased the irreversible fouling ratio from 60.7% to 19.4% and showed a high HA removal efficiency of approximately 90.5%. The Hermia model confirmed that the cake formation mechanism best described the experimental data for the neat PVC and nanocomposite membranes with the presence and absence of the PAC coagulant. This confirms that the PAC coagulant can significantly mitigate fouling and improve HA removal in the submerged membrane system.

Application of Polyaluminium Chloride Coagulant in Urban River Water Treatment Influenced the Microbial Community in River Sediment

Polyaluminium chloride (PAC) has been widely used as a chemical coagulant in water treatment. However, little is known about the impact of PAC performance on the microbial community in sediments. In this study, the archaeal, bacterial, and fungal communities in urban river sediments with and without PAC treatment were investigated. Prokaryotic diversity decreased at the PAC addition site (A2) and increased along with the river flow (from A3 to A4), while eukaryotic diversity was the opposite. The abundance of core microbiota showed a similar trend. For example, the dominant Proteobacteria presented the highest relative abundance in A1 (26.8%) and the lowest in A2 (15.3%), followed by A3 (17.5%) and A4 (23.0%). In contrast, Rozellomycota was more dominant in A2 (56.6%) and A3 (58.1%) than in A1 (6.2%) and A4 (16.3%). Salinity, total dissolved solids, and metal contents were identified as the key physicochemical factors affecting the assembly of core microorganisms. The predicted functions of archaea and fungi were mainly divided into methane cycling and saprotrophic nutrition, respectively, while bacterial function was more diversified. The above findings are helpful to enhance our understanding of microorganism response to PAC and have significance for water treatment within the framework of microecology.

Pengolahan Limbah Cair Industri Minyak Sawit Menggunakan Reaktor Listrik Plat Kolom Secara Kontinu serta dengan Penambahan PAC

Palm oil industrial waste contains various dissolved compounds in the form of short fibers, hemicellulose, and their derivatives, proteins, free organic acids, a mixture of minerals and organic pigments such as anthocyanins, carotenes, polyphenols, lignins and tannins. Organic compounds in this waste will cause problems such as an increase in TSS, COD values which can pollute the environment. The electrocoagulation method has the potential to reduce TSS, TDS, COD content and neutralize pH. The purpose of this study was to determine the effect and optimum conditions of the electrocoagulation process with variations in flow rate, voltage, spacing between plates and the addition of poly aluminum chloride (PAC) coagulants to decrease TSS, COD and pH parameters so that they meet the quality standards of waste in Permen LH. No. 5/2014. The method used is a continuous electrocoagulation process using an aluminum catalyst and the addition of PAC. The variables used in this study were the stress variable (24; 26; 28 V) and the variable flow rate velocity (0.3; 1,2; 2.5 L / min) and the variation of the spacing between the plates (2, 3, 4 cm). The results of this study found that the optimum conditions were obtained at a voltage of 28 volts and a flow rate of 0.3, and a distance between the plates of 2 cm and the addition of 400 ppm PAC with a percentage of TSS removal of 92.093% from 2150 mg / L to 170 mg / L, and a decrease in COD of 85.343% from 1310 mg / L to 192 mg / L. The results obtained show that it is in accordance with the standards of the Ministry of Environment and Forestry Regulation No.5 of 2014.

Inline dosing of powdered activated carbon and coagulant prior to ultrafiltration at pilot-scale – Effects on trace organic chemical removal and operational stability

Hybrid membrane processes such as inline dosing of powdered activated carbon (PAC) prior to ultrafiltration membranes (UF) have already shown promising potential for the abatement of trace organic chemicals (TOrCs). However, questions regarding the optimization of the operational stability by the employment of coagulation and its interferences with inline dosed PAC, have not yet been comprehensively investigated. Within the scope of this pilot-scale study, inline dosing of different sized PAC types at different dosages was combined with or without the addition of polyaluminium chloride (PACl) coagulant prior to UF. As expected, when PAC was not employed, negligible TOrC removal was observed, whereas all the operational modes with the application of PAC inline dosing showed significant TOrC removal. Coagulation with PACl clearly reduced the build-up of transmembrane pressure, especially owing to maintaining hydraulic backwash efficiency. The operational mode of precoating the UF with PACl combined with continuous inline dosing of PAC exhibited particularly good TOrC removal results along with optimized membrane fouling mitigation. In contrast, the simultaneous and continuous dosing of PAC and PACl is not recommended, in particular owing to detrimental effects of the coagulant on TOrC removal efficiency by PAC.

Polyaluminium Chloride and Anionic Polyacrylamide Water Treatment Residuals as a Sorbent for Cd2+ and Zn2+ in Soils

Water treatment residuals produced after addition of polyaluminium chloride and anionic polyacrylamide (PAC-APAM WTRs) were evaluated for the potential to remove Cd2+ and Zn2+ from aqueous solutions by batch adsorption studies. The maximum adsorption capacity obtained from Langmuir modeling was 85.5 mg Cd2+/g PAC-APAM WTRs or 25.6 mg Zn2+/g PAC-APAM WTRs. A Dubinin-Radushkevich (D-R) model study showed that the adsorption process was chemically controlled. The pseudo-second-order model described the adsorption kinetic data better than the pseudo-first-order model, while kinetic studies showed that the adsorption process included external surface adsorption and intraparticle diffusion, which was likely the rate-limiting step. PAC-APAM WTRs adsorbed Cd2+ and Zn2+ in the pH range of 3–9 and in the temperature of 20–40 °C, and the immobilization ability for both ions increased with the increase of pH or an increase in temperature. FT-IR spectroscopy analysis illustrated that the carboxyl groups from APAM in WTRs participated in the adsorption reactions in addition to Fe(Al)-O functional groups and O–H groups. This short-term study showed that PAC-APAM WTRs could be a cost-effective media for the remediation of Cd2+ and Zn2+ contaminated soils. Further studies are needed to examine the slow adsorption mechanisms and determine the optimum mass ratio of soil to PAC-APAM WTRs under various soil conditions.

Synergistic fouling behaviors and mechanisms of calcium ions and polyaluminum chloride associated with alginate solution in coagulation-ultrafiltration (UF) process

Effects of calcium ions and polyaluminum chloride (PACl) on membrane fouling in coagulation-ultrafiltration (UF) process were investigated in this study. Filtration tests demonstrated three interesting filtration behaviors: 1) high specific filtration resistance (SFR) of alginate solution with low CaCl2 or PACl addition (e. g. 3.51×1015 m·kg -1 under the condition of 1.5 mM CaCl2 addition); 2) unimodal pattern of alginate SFR with PACl or CaCl2 addition alone; 3) synergistic effects between CaCl2 and PACl on alginate SFR. It was found that, the foulant morphological changes driven by the thermodynamic mechanisms based on Flory-Huggins lattice theory take the critical roles in these filtration behaviors. Density functional theory (DFT) calculations showed that initial coordination of Ca2+ and Al3+ ions with alginates tended to form tetrahedron geometry and geometry of coordinating three terminal carboxyl groups, respectively, which facilitated to elongate the alginate chains (without clustering the flocs) and form more stable gel, increasing SFR. Improving Ca2+ and Al3+ dosages triggered transition to other geometries for clustering polymeric network and flocculation, reducing SFR. Due to the higher binding affinity of Ca2+ over Al3+, Ca2+ and Al3+ sequentially take roles of enlarging polymeric network and clustering the coordination compounds, and then facilitate to form large size flocs and reduce SFR, causing the synergistic effects between CaCl2 and PACl additions. The proposed thermodynamic mechanisms satisfactorily explained these interesting fouling behaviors, allowing to further optimize coagulation-UF process.

Anaerobic digestibility of up-concentrated organic matter obtained from direct membrane filtration of municipal wastewater

Direct membrane filtration (DMF) process is a promising technology for up-concentration and recovery of organic matter (OM) from municipal wastewater. This study investigates anaerobic digestibility of up-concentrated OM obtained from the DMF process. Effluent from a primary sedimentation basin was used as feed water. Effect of polyaluminum chloride (PACl) addition to the DMF process on the anaerobic digestibility of obtained up-concentrated OM was also investigated because PACl is sometimes used as a coagulant in the DMF process for improving effluent quality and OM recovery, and for mitigating membrane fouling. Batch anaerobic digestion experiments were conducted to achieve these objectives. Fitting the obtained data to the reaction curve model revealed that maximum biogas production based on feed volatile solids (VSfed) from up-concentrated OM containing PACl reached 0.56 L-Biogas/g-VSfed, which was higher than from up-concentrated OM without PACl (0.47 L-Biogas/g-VSfed), waste activated sludge (0.35 L-Biogas/g-VSfed), and mixed sludge (0.48 L-Biogas/g-VSfed). Methane yield based on degraded VS (VSdeg) of up-concentrated OM containing PACl was 0.56 L-CH4/g-VSdeg, which was also highest. These results indicate the up-concentrated OM obtained from the DMF process has high potential for biogas production, and the addition of PACl in the DMF process (∼4.3 mg-Al/L) could enhance the biogas production.

Enhanced coagulation by two-stage alum addition: the role of solution pH, floc breakage and assistant of non-ionic polyacrylamide

ABSTRACT Coagulation process is highly influenced by solution pH, floc breakage, and coagulant aid. In this work, two-stage addition of alum-based coagulants, polyaluminum chloride (PACl) and aluminum sulfate (Al2(SO4)3), was compared to their one-stage addition with the same total dosage. The dose ratio of primary and secondary addition was optimised. The effects of solution pH, floc breakage and dosing timing of coagulant aid of non-ionic polyacrylamide (NPAM) on coagulation efficiency and floc property were investigated. The results showed that two-stage addition of PACl showed less sensitivity with the variation of pH. Compared to PACl, two-stage addition of Al2(SO4)3 was more sensitive to the solution pH, especially when the pH ranged from 7 to 10. For all cases, the presence of floc breakage improved the removal of colloidal particles. The coagulation mechanism of primary coagulant was charge neutralisation, while other mechanism was involved with the secondary addition of coagulant. Compared to one-stage addition, the settling performance of aggregates and particulates removal in two-stage addition was more effective with the variation of dosage or dosing timing of NPAM. The present work provides detailed operating parameters for this coagulation strategy.