Determination of the Efficiencies of Clay and PFCL or PACL with Na2CO3 Flocculent in the Removal of TSS from the AMD

Abstract: The experiment was conducted on the acid mine drainage (AMD) that was sampled from the Krugersdorp decant in South Africa. Five 500 ml glass beakers were filled with 200 ml of AMD sample and dosed with synthetic flocculent of FeCl3 and Na2CO3 (PFCl) and treated in jar test (exp. A). pH, conductivity, total suspended solids (TSS), dissolved oxygen (DO) and oxidation reduction potential (ORP) were measured after treatment and an hour settling. Another identical set of experiments was carried out with a combination of clay and PFCl dosage (exp. B). A third similar set of experiments was conducted with dosages of a combination of clay with PFCl or clay with AlCl3 and Na2CO3 (PACl) including another set of experiments using five 500 ml Erlenmeyer flasks in a shaker (exp. C). The pH results of the samples dosed with PFCl are relatively lower than that of the samples with a combination of clay and PACl dosage. The pH changing pattern with PFCl exhibited an increasing rate with increasing dosage whereas the pH of the sample dosed with a combination of clay and PFCl decreases with increasing dosage. The results show that bentonite clay does not have significant impact on pH of the samples. The ORP in treated AMD samples of experiments A and B is lower than in raw AMD sample. Residual TSS of the AMD samples which were treated with mixing are similarly identical to those of the samples treated on a shaker. TSS removal of the AMD samples with clay and PFCl is better than that with FeCl or PACl only

The Effect of the Bentonite Clay Constituents in a Flocculent of FeCl3 and CaMg.2(OH)2 during AMD Treatment Ntwampe OI1, Waanders FB2 and Bunt JR2

Abstract: Two sets of experiments were conducted by pouring 200 mL of the acid mine drainage (AMD) decant from Krugersdorp (South Africa) into five 500 mL beakers (mixing) and Erlenmeyer flasks (shaking) and dosed with 20- 60 mL of FeCl3, Fe2(SO4)3, CaMg.2(OH)2 and a combination of FeCl3 with CaMg.2(OH)2 (af-PFCl) respectively. The samples were placed in a flocculator and a shaker and stirred at 250 rpm for 2 minutes respectively, settled for 1 hour and the pH, conductivity and turbidity were measured. A third similar set of experiments was conducted without mixing settled for 1 hour and the same measurement taken. The fourth and fifth sets of experiments were conducted with CaMg.2(OH)2 and afPFCl flocculent respectively. The novelty of this study is to determine the turbidity removal efficiency using FeCl3 and CaMg.2(OH)2 in a form of unprocessed polymers. The results showed that the pH and residual turbidity in the samples with Fe3+ salts, CaMg.2(OH)2 is relatively identical to those in the samples with af-PFCl dosages. The turbidity removal efficiencies exhibited by the Fe salts, CaMg.2(OH)2 and af-PFCl were optimal. The pH and residual turbidity in the AMD samples with mixing, shaking and without mixing indicate that destabilization-hydrolysis is influenced by the physico-chemical properties of the solution, whereas mechanical agitation mainly disperses the reagent(s). Optimal turbidity removal of the samples without mixing also indicates that perikinetic flocculation is a predominant process during aggregation/flocs formation

Biodefoamer-Supported Activated Sludge System for the Treatment of Poultry Slaughterhouse Wastewater

Poultry slaughterhouse wastewater (PSW) is laden with fats, oil, and grease (FOG), as well as proteins. As such, PSW promotes the proliferation of filamentous organisms, which cause foam formation. In this study, the production of biological defoamers (biodefoamers) uses a consortium with antagonistic properties, i.e., 1.39 L of wastewater/mL defoamers, as reported in our previous study, toward foam formers and their application in the treatment of PSW using a bench-scale activated sludge (AS)-supported treatment system consisting of an aeration and clarification tank. The foam produced was slimy, brown, and thick, suggesting the presence of Nocardia, Microthrix, and Type 1863 species in the PSW/AS wastewater treatment system. The bio (Bio-AS) and synthetic-defoamers (Syn-AS, positive control) supplementation, i.e., at 4% in the PSW/AS primary treatment stage (aeration tank) operated over ten days, resulted in 94% and 98% FOG and protein removal for the biodefoamers, respectively, when compared to 50% and 92% for a synthetic defoamer, respectively. Similarly, the Bio-AS treatment achieved 85.4% COD removal, while a lowly 51% was observed for the Syn-AS PSW treatment regime. Overall, the biodefoamers performed vehemently compared to synthetic defoamers, improving the PSW/AS system’s performance. It was prudent to hypothesize that the biodefoamers might have had FOG solubilization attributes, an assertion that needs further research in future studies. It was concluded that Bio-AS was more efficient in the removal of FOG, proteins, TSS, and COD in comparison to Syn-AS and negative control without supplementation (CAS)

Turbidity Removal Efficiency of Clay and a Synthetic af-PACl Polymer of Magnesium Hydroxide in AMD Treatment

Abstract: In this study five 200 mL acid mine drainage (AMD) samples were treated with 5g clay (bentonite) alone or mixed with 0.1 M Al 3+ in AlCl3 and 0.1 M Mg 2+ in Mg(OH)2 polymer. The AMD samples were poured into five 500 mL glass beakers and dosed with 5 g/L of clay in a jar test, (250 rpm for 2 minutes and reduced to 100 rpm for 10 minutes) and the samples were allowed to settle for 1 hour after which the pH, conductivity, turbidity, dissolved oxygen (DO) and oxidation reduction potential (ORP) were measured. In the next step, 200 mL of the supernatant was poured into five 500 mL glass beakers and dosed with a af-PACl (acid-free polyaluminiumchloride) polymer of 0.1 M Al 3+ in AlCl3, mixed with 0.1 M Mg 2+ in Mg(OH)2, and treated in a similar manner in a jar test, settled for 1 hour, after which similar measurements were conducted, depicted as experiment (A). Another similar set of experiments was conducted, where the AMD sample was dosed with a polymer of 5 g of clay, 0.1 M Al 3+ in AlCl3 and 0.1 M Mg(OH)2 in a jar test. Similar measurements were conducted after 1 hour of settling, depicted as experiment (B). The results showed that the addition of the clay to the AMD sample as a reagent (A) or a polymeric component (B) does not affect the turbidity removal, but the rate of hydrolysis (pH changing pattern) and ORP are affected. The experimental results showed that there is a correlation between the ORP and the pH, and also showed that oxidation takes place during the destabilization-hydrolysis process. The results also showed that the conductivity plays a role during the destabilization-hydrolysis process, i.e. correlation between changing rate of the conductivity and the turbidity. Keywords: mixing, disperse, turbidity, multivalent, pH, turbidity Introduction Conventional wastewater treatment using inorganic coagulants is a common practice because aluminium, one of the reagents utilized in the process is in abundance and has also exhibited desirable effectiveness in the wastewater treatment. On the other hand, the use of polymeric flocculants over inorganic polyelectrolytes, such as poly-aluminium complexes, gives significant advantages when the water has a high concentration of suspended solids; the concentration of the polymeric flocculent is lower, the resulting sludge is more compact and there is less coagulant left in the water after treatment According to Eqs. 1 and 2, it is envisaged that there is a high volume of AMD generated as oxidation of FeS2 occurs in two reactions. Notwithstanding, the chemical reactions (Eqs. 1 and 2), which results in the production of AMD, bacterial oxidation is also inevitable, and occurs at pH values of less than 3.5. AMD contains different minerals and also has a high ionic movement, which results in a highly reactive tendency The physico-chemical properties of the wastewater play a pivotal role during wastewater (AMD) treatment, as they interact amongst themselves to transform the metals/compounds to another phase and the reaction efficiency of reagents which are dosed to wastewater treatment (coagulation-flocculation process) determines the quality of the treated effluent. Coagulation-flocculation is a process which leads to nucleation, crystal growth and aggregation of the destabilised suspended particles in the solution 90 which is corroborated by the study conducted by A choice of an effective coagulant/flocculent is very significant as it has to destabilize the colloidal suspension. Destabilization is a process where a stable colloidal suspension occurs, which is caused by the equilibrium state between van der Waals forces of attraction and electrostatic forces of repulsion. The ionic charges from these forces form two layers namely, diffuse double and stern layers which form electrical double layer (EDL). An EDL ( q = charge on the particle, d = thickness of the layer surrounding the shear plane and D = dielectric constant of liquid. The force field of like charges in an aqueous solution ( = potential at a point in the diffuse layer versus infinity at the bulk solution, x = charge density at the same point, ρ = density and ԑ = permittivity. In Eq. 4 the charge density at the potential ȥ is described by Eq. 5. The number of positive and negative ions in the diffuse layer is distributed according to the MaxwellBoltzmann distribution (Eq. 6 for cations and Eq. 7 for anions): n+ -n-*exp (− ) n+ and n-= are respective numbers of positive and negative ions per unit volume at the point where potential is ψ, n0 = the concentration of ions at the infinity (bulk solution), z = the valence of the ions, e = the charge of electron, k = Boltzmann's constant and T = temperature. The potential of the particle surface versus the bulk solution is called the Nernst potential (ψ0). The outer Helmholtz plane (OHP) is found between the inner layer and the outer layer, which has potential of the particle surface versus bulk solution. However, this potential cannot be directly measured and therefore a common parameter, which depicts the surface charge of the colloid, is surface-potential ψζ), which is the electrical potential between the plane of shear and the bulk solution. The diffuse part of the double layer is analogous to the plate condenser. Even though in reality the double layer extends to infinity, the Debye-Hückel length, K -1 , is used to describe the thickness of the double layer Field et al., (1988), expressed by Eq. 8. In the present study, an acid-free polymer of AlCl3 and Mg(OH)2 was prepared, which was also mixed with bentonite clay and dosed in each AMD sample. Unlike the costly commercial polymers (PFCl or PACl) which are prepared by partial hydrolysis of acidic aluminium chloride or ferric chloride solution in a special reactor, the polymers utilized in this study (clay, AlCl3 and Mg(OH)2) are easy to prepare and affordable as they are prepared by directly mixing the reagents and are then ready for use. Apart from commonly employed parameters in AMD treatment such as the pH, conductivity and turbidity, the effect of the dissolved oxygen (DO) and oxidation reduction potential (ORP) are investigated in the present study. The DO has been used as a controlling and/or monitoring parameter for many other different treatment systems such as high sulphate wastewater treatment systems MATERIALS AND METHODS In this study, coagulation-flocculation treatment has been applied to an AMD sample using 5 g clay (bentonite), 20, 30, 40, 50 and 60 mL of 0.10 M Al 3+ in AlCl3 and 0.10 M Mg 2+ in Mg(OH)2 dosages respectively. The pH, conductivity, turbidity, zeta potential and dissolved oxygen (DO) of the samples were measured before and 1 hour after treatment. A one litre AMD sample was poured into a litre glass beaker, 5.0 g of clay added to the sample and mixed in a flocculator at 250 rpm for 2 minutes and reduced to 100 rpm for 10 minutes. The sample was allowed to settle for 1 hour after which 200 mL of the supernatant was poured into five 500 mL glass beakers. Dosages of 20, 30, 40, 50 and 60 mL afPACl synthetic polymer were added to the samples using 100 mL plastic syringes respectively. The samples settled for 1 hour, and then the pH, conductivity, turbidity, zeta potential and DO were measured. A similar set of experiments was conducted using a synthetic polymer made of a mixture of 5.0 g clay, 0.10 M Al 3+ in AlCl3 and 0.10 M Mg 2+ in Mg(OH)2. Similar measurements were conducted before and after 1 hour settling from a jar test. AMD sampling The samples were collected from the Western Decant in Krugersdorp in a 25 litres plastic drum. The sample was air-tied and stored at room temperature. The pH, conductivity, turbidity, ORP and DO of the AMD sample before mixing were 2.08, 4.94 mS/cm, 105 NTU, 234 mV and 4.5 mg/L respectively. Coagulants Inorganic coagulants of 0.10 M of Al The equipment used for the jar tests was a BIBBY Stuart Scientific Flocculator (SW1 model), which has six adjustable paddles with rotating speeds between 0-350 rpm. A 200 mL sample of AMD containing 6.3 g of solid particles was poured into each of the five 500 mL glass beakers for the test. Rapid mixing was set at 250 rpm for 2 minutes, followed by slow mixing at 100 rpm for 10 minutes, a normal standard recommended in a jar test. Experiments Experiment (A): Jar test with clay and afPACl polymer dosed separately The pH, conductivity, turbidity, zeta potential and DO of the sample were measured. Five 500 mL glass beakers were filled with 200 mL samples of AMD with parameters mentioned under sub-section 2.1. A 1.2 L of AMD sample was dosed with 5 g pulverized clay and treated in a jar test at 250 rpm for 2 minutes and reduced to 100 rpm for 10 minutes. The sample was allowed to settle for 1 hour after which 200 mL of the supernatant was poured into five 500 mL glass beakers. The samples were dosed with 20, 30, 40, 50 and 60 mL of 0.10 M af-PACl synthetic polymer of Mg(OH)2. The samples were allowed to settle for 1 hour, after which the measurements were conducted. Experiment (B): Jar test with a polymer of clay and af-PACl polymer dosage A similar set of experiments, where 5 g of clay was mixed with 0.10 M Al 3+ in AlCl3 and 0.10 M of Mg 2+ in Mg(OH)2 to produce a synthetic polymer, was used. A 200 mL of AMD sample was poured into five 500 mL glass beakers, treated in a jar test at 250 rpm for 2 minutes and reduced to 100 rpm for 10 minutes. The samples settled for 1 hour after which similar measurements were conducted. Performance evaluation The pH was used as a determinant to assess the rate of hydrolysis and hydrolytic potential of the coagulants (Al 3+ and Mg 2+ salts) at different mixing duration, whereas the concentration and turbidity were measured to determine the ionic potential and removal of colloidal particles from the samples respectively. pH measurement A SensoDirect Multimeter (made in South Africa) pH/ORP/DO/CD/TDS meter with an electrode filled with silver chloride solution and the outer glass casing with a small membrane covering at the tip was used. The equipment was calibrated with standard solutions with pH of 4.0 and 7.0 before use. Conductivity A similar Multimeter instrument as described in subsection 3.3.1 was used. The CD probe was connected and the measurement was selected using the appropriate button, and the CD reading was displayed. Dissolved oxygen A similar Multimeter instrument as described in subsection 3.3.1 was used. The DO probe was connected and the measurement was selected using the appropriate button, and the DO reading was displayed. Oxidation reduction potential A similar Multimeter instrument as mentioned in subsection 3.3.1 was used. The ORP probe was connected and the measurement was selected using the appropriate button, and the ORP reading was displayed. Turbidity measurement A Merck Turbiquant 3000T Turbidimeter (made in Japan) was used to determine turbidity or the suspended particles in the supernatant, using NTU as a unit of measure. It was calibrated with 0.10, 10, 100, 1000 and 10000 NTU standard solutions. RESULTS Turbidity Removal Efficiency of Clay and a Synthetic af-PACl Polymer of Magnesium Hydroxide in AMD Treatment http://www.ijSciences.com Volume 4 -September 2015 DISCUSSION The main objective in this study is the investigation of the micro-and macro-chemical reactions which cause the destabilization-hydrolysis reaction. This will then make it easier to elucidate on the physicochemical interactions occurring during the coagulation-flocculation process, a precursor to nucleation, crystallization and sedimentation/settling; a chain reaction which is still unclear in wastewater treatment. The studies which have been conducted are mainly to investigate the best technologies and reagents (coagulants/flocculants/aids) to be employed in wastewater treatment, an approach not contemplated in this study. In this study the focus is on the physico-chemical strength mechanisms of the respective reagents (af-polymers) to effectively destabilize the double layer of the aqueous colloids, thereby weakening the repulsive forces and promote agglomeration. In a normal coagulation-flocculation process with coagulant/flocculent, (counter ionic to the charges of the colloids) the volume of the diffuse layer which maintains electro-neutrality is lowered, the thickness of the diffuse layer is reduced and the van der Waals force becomes predominant, causing the net force to become attractive. The effectiveness of the process determines the rate of agglomeration and adsorption (turbidity removal). The turbidity removal efficiency The strength of the reagent can arbitrarily be explained by the ability to weaken the electrostatic forces of the aqua-colloid 2+ ) after being added to the AMD sample. Eqs. 3-7 show that the reactivity of the coagulant/flocculent is influenced by physicochemical properties, such as the charge on the particle, thickness of the layer surrounding the shear plane, dielectric constant of liquid, concentration and valence of the ions, charge of the electron and temperature. The type of colloids, hydrophilic or hydrophobic, plays a pivotal role during the destabilizationhydrolysis-crystallization in wastewater treatment. The type of coagulant/flocculent is also essential and should be compatible to neutralize the electrostatic repulsive forces which keep the colloids apart. This has been confirmed by the work conducted by MgCl2(aq) + 2 H2O ↔ Mg(OH)2(s) + 2 HCl(aq) The Mg(OH)2(aq) (Eq. 11) is actually in the form of Mg 2+ (aq) and OH -(aq), where Mg 2+ ions dissolve in the AMD solution and hydrolyse to form Mg(OH)2(s) precipitates (Eq. 12), which react with Al(OH)3(s) to form an acid-free polymer. These chemical reactions indicate that the af-PACl polymer of Mg(OH)2 behaves partially as a coagulant due to the presence of the cationic Al 3+ and Mg 2+ ions. This is a very cost effective polymer, which doesn't require a sophisticated production process that includes a special reactor and restricted operating conditions. As Eq. 11 showed that there is double hydrolysis taking place, the effective turbidity removal 2+ ions in a polymer. The turbidity results also predict that charge neutralization, enmeshment in a precipitate and adsorption and inter-particle bridging are the predominant reactions during destabilization. The turbidity results The differential pH values between the untreated AMD sample (2.08) and the treated AMD sample of experiment (A) decreased with increasing dosage in a range of 2.86-3.79, whereas the pH in the AMD samples of experiment (B) increased in a range of 2.54-3.68. The decreasing and increasing trends of the pH in experiments (A) and (B) respectively is attributed to the clay mineral, because it is the only reagent changing the dosing used [dosed alone as reagent-experiment (A), and dosed as a polymer with FeCl3 and Mg(OH)2-experiment (B)]. The inference to this is that the clay minerals have the ability to adsorb the (H + ) ions in the solution, the chemistry of its adsorption potential behaved differently when added alone, compared to when added as a polymer 96 In In In In In The SEM micrographs show flocculent branching which plays a key role since it is largely controlling the polymer interaction behaviour with the particles. It is suggested that the branching induces important differences in the floc structure, compactness, and fractal dimensions, which affect the sedimentation rates and floc strength. The potential impact of the solution ionic strength is due to the presence of dissolved ions of a multivalent electrolyte (Al 3+ and Mg 2+ salts) in the solution also plays a pivotal role. The SEM micrograph 10A is the AMD sludge in experiment (A) showing dense and small flocs located apart, dense on the left and small on the right, with very few cavities. The SEM micrograph 10B represents the AMD sludge in experiment (B), where there are dense flocs distributed throughout the slide with a limited number of cavities. The two micrographs show a sponge-cake like structure linked together, showing adsorption efficiency of more than 85 %. The cavities showed that they are sealed as going downward, showing no or insignificant amount of turbid materials which can pass through the adsorbate. In The Pearson correlation coefficient (r) is used to calculate the relation between pH and residual turbidity, using Eq. 13. The r-value obtained for the AMD samples CONCLUSION The efficiency of the af-PACl polymer exhibited by the experimental results obtained in this study can be explained by the hydrolysis of both metal ions (Al 3+ and Mg 2+ ) after being added to the AMD sample. The results showed that the addition of the clay to the AMD sample as a reagent (A) or a polymeric component (B) does not affect the turbidity removal, but the rate of hydrolysis (pH changing pattern) and ORP. The experimental results showed that there is a correlation between the ORP and the pH, and also showed that oxidation takes place during the destabilization-hydrolysis process. The results also showed that the conductivity plays a role during the destabilization-hydrolysis process, (correlation between changing rate of the conductivity and the turbidity). The DO observation results of experiments (A) and (B) showed that there is an ingress or release of O2 during hydrolysis-nucleation-adsorption

Prediction of biogas production from co-digestion of winery solid waste and zebra manure using modified gompertz model (GM) and logistic equation (LE)

The effect of anaerobic co-digestion (ACoD) of winery solid waste (WSW) and Zebra manure (ZM) on the enhancement of biogas production was investigated. Biogas was produced by means of an automated single batch anaerobic digester equipped with a pH and temperature control. The fermentation of WSW and ZM was conducted as mono anaerobic digestion (MAD) separately as well as ACoD (1WSW: 2ZM) at 37°C for 30days. Gas production was predicted using Gompertz Model (GM) and Logistic Equation (LE) and measured through downward displacement of acidified water. Results showed the ACoD (1WSW: 2ZM) method produced higher amount of cumulative biogas (952.6mL) as compared to MAD with 30.4mL for WSW and 139.9mL for ZM respectively, after 30 days of retention time. A close fit between the predicted and measured biogas values was observed with correlation coefficient of 0.965 and 0.953 for GM and LE model respectively. Hence, the models can be used to predict biogas yields from ACoD of biodegradable organic waste and ZM. The findings showed the effect of combining WSW with ZM, which could provide essential information and direction for scaling up of biogas production by high-performance ACoD systemNational Research Foundation (NRF) of SouthAfric

Biodefoamer-Supported Activated Sludge System for the Treatment of Poultry Slaughterhouse Wastewater

Poultry slaughterhouse wastewater (PSW) is laden with fats, oil, and grease (FOG), as well as proteins. As such, PSW promotes the proliferation of filamentous organisms, which cause foam formation. In this study, the production of biological defoamers (biodefoamers) uses a consortium with antagonistic properties, i.e., 1.39 L of wastewater/mL defoamers, as reported in our previous study, toward foam formers and their application in the treatment of PSW using a bench-scale activated sludge (AS)-supported treatment system consisting of an aeration and clarification tank. The foam produced was slimy, brown, and thick, suggesting the presence of Nocardia, Microthrix, and Type 1863 species in the PSW/AS wastewater treatment system. The bio (Bio-AS) and synthetic-defoamers (Syn-AS, positive control) supplementation, i.e., at 4% v/v in the PSW/AS primary treatment stage (aeration tank) operated over ten days, resulted in 94% and 98% FOG and protein removal for the biodefoamers, respectively, when compared to 50% and 92% for a synthetic defoamer, respectively. Similarly, the Bio-AS treatment achieved 85.4% COD removal, while a lowly 51% was observed for the Syn-AS PSW treatment regime. Overall, the biodefoamers performed vehemently compared to synthetic defoamers, improving the PSW/AS system’s performance. It was prudent to hypothesize that the biodefoamers might have had FOG solubilization attributes, an assertion that needs further research in future studies. It was concluded that Bio-AS was more efficient in the removal of FOG, proteins, TSS, and COD in comparison to Syn-AS and negative control without supplementation (CAS)

Sustainable Approach to Eradicate the Inhibitory Effect of Free-Cyanide on Simultaneous Nitrification and Aerobic Denitrification during Wastewater Treatment

Simultaneous nitrification and aerobic denitrification (SNaD) is a preferred method for single stage total nitrogen (TN) removal, which was recently proposed to improve wastewater treatment plant design. However, SNaD processes are prone to inhibition by toxicant loading with free cyanide (FCN) possessing the highest inhibitory effect on such processes, rendering these processes ineffective. Despite the best efforts of regulators to limit toxicant disposal into municipal wastewater sewage systems (MWSSs), FCN still enters MWSSs through various pathways; hence, it has been suggested that FCN resistant or tolerant microorganisms be utilized for processes such as SNaD. To mitigate toxicant loading, organisms in SNaD have been observed to adopt a diauxic growth strategy to sequentially degrade FCN during primary growth and subsequently degrade TN during the secondary growth phase. However, FCN degrading microorganisms are not widely used for SNaD in MWSSs due to inadequate application of suitable microorganisms (Chromobacterium violaceum, Pseudomonas aeruginosa, Thiobacillus denitrificans, Rhodospirillum palustris, Klebsiella pneumoniae, and Alcaligenes faecalis) commonly used in single-stage SNaD. This review expatiates the biological remedial strategy to limit the inhibition of SNaD by FCN through the use of FCN degrading or resistant microorganisms. The use of FCN degrading or resistant microorganisms for SNaD is a cost-effective method compared to the use of other methods of FCN removal prior to TN removal, as they involve multi-stage systems (as currently observed in MWSSs). The use of FCN degrading microorganisms, particularly when used as a consortium, presents a promising and sustainable resolution to mitigate inhibitory effects of FCN in SNaD