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1

Optimizing Electrodialytic Recovery of Mineral Ions from Bittern Wastewater Using D-Optimality Design

Anggrainy Anita Dwi, Sinatria Afrah Zhafirah, Bagastyo Arseto Yekti, Mohd-Zaki Zuhaida

Journal of Ecological Engineering

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2023

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Vol. 24, nr 10

369--379

EN

Electrodialysis has been proven effective due to its high selectivity for separating monovalent and divalent ions. This study statistically evaluated the simultaneous electrodialytic recovery of mineral ions from bittern wastewater. The objective was to investigate the effect of cell number, anode materials, and applied voltage to optimize mineral ion recovery. A D-optimality design response surface methodology was performed to estimate the model parameter and identify the factors contributing to mineral ions recovery. The effects of independent variables and their interactions on the responses were investigated using ANOVA. All developed models were highly significant, with a p-value of <0.0001. The applied voltage was considered very important for the recovery process of all mineral ions as it affects the driving force of ion migration through the ion-exchange membrane. The optimization analysis (desirability value of 0.967) revealed 12% Cl–, 14% SO4 2–, 0.7% Mg2+, and 21% Ca2+ recovery at the combination of 5-cells configuration, graphite electrode, and 9 V.

2

The Role of Boron-Doped Diamond and Platinum Anodes in the Three-Compartment Electrochemical Pretreatment of Stabilized Landfill Leachate – Response Surface Methodological Approach

Bagastyo Arseto Yekti, Anggrainy Anita Dwi, Rosyidah Badriyah

Journal of Ecological Engineering

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2022

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Vol. 23, nr 12

50--60

EN

Stabilized landfill leachate contains high fractions of refractory organics that cannot be effectively degraded by simple biological or physicochemical treatment. Thus, primary treatment was required to improve biodegradability and enhance treatment efficiency. This study investigated the role of Boron-Doped Diamond (BDD) and platinum (Pt) anodes at a current density of 29.2 and 33.3 mA/cm2 in the electrochemical processes for the pretreatment of stabilized leachate. A three-compartment electrochemical reactor was used in the research to enhance the removal of ionic pollutants. The pollutants were measured as total dissolved solids (TDS), chemical oxygen demand (COD), ammonium-nitrogen (NH4–N), and nitrite (NO2–). The reactor performance was then analyzed using a regular two-level factorial design. The results showed that the electrochemical process effectively removed organic and inorganic pollutants. The highest removal was obtained at 33.3 mA/cm2 using the BDD, measured around 48, 82, 60, and 79% for TDS, COD, NH4–N, and NO2–, respectively. Meanwhile, the specific energy consumption for COD removal was estimated to reach 1.5 and 1.55 Wh/g for BDD and Pt, respectively. These results imply that the type of anodes and applied current densities significantly influence the treatment efficiency.

3

The Performance of Electrocoagulation Process in Removing Organic and Nitrogenous Compounds from Landfill Leachate in a Three-Compartment Reactor

Bagastyo Arseto Yekti, Sidik Fahrudin, Anggrainy Anita Dwi, Lin Jr-Lin, Nurhayati Ervin

Journal of Ecological Engineering

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2022

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Vol. 23, nr 2

235--245

EN

In this study, the effectiveness of the electrocoagulation (EC) process was evaluated based on the reduction of organic and nitrogenous contaminants in landfill leachate. A three-compartment electrochemical reactor as pre-treatment of stabilized landfill leachate was carried out ahead of biological treatment. The removal efficiencies of COD, BOD, ammonia, and nitrate were analyzed at pH 4, 6, and 8 with the current densities of 20.83 and 29.17 mA•cm–2. At pH 4, the highest removal of COD and NH4+ was obtained, i.e., in the range of 72–81% and 43–59%, respectively. The ratio of BOD5/COD was increased after EC, from initially 0.11 to 0.32 at pH 4. In addition, EC effectively removed humic substances in the leachate by targeting a large amount of high molecular weight humic substances, with around 103 kDa. However, the higher removal efficiency observed at higher current density leads to higher specific energy consumption. At a current density of 29.17 mA•cm–2, the specific energy consumption obtained in EC was around 10–17 Wh•g–1 COD and 99–148 Wh•g–1 NH4+. This could be decreased up to 50% at an applied current density of 20.83 mA•cm–2 with slightly lower efficiencies.

4

Recovery of Alum Sludge by Using Membrane-Based Electrochemical Process

Bagastyo Arseto Yekti, Ayu Adi Puspitarini, Barakwan Rizkiy Amaliyah, Trihadiningrum Yulinah

Journal of Ecological Engineering

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2020

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Vol. 21, nr 6

237--247

EN

The use of aluminum sulfate (Al2SO4) coagulant in water treatment plants generates large amount of sludge residues containing the alum hydroxide precipitates and organic matter. Due to its amphoteric characteristic, this sludge by-product offers alum coagulant recovery by using electrochemical process, before safe disposal to the environment. This study is aimed at evaluating the efficiency of membrane-based electrochemical processes to recover aluminum from the filtrate of the acidified sludge. The dried alum sludge was acidified using sulfuric acid at pH 3, and then centrifuged to obtain the filtrate. Organic content of the filtrate was measured by means of Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD), i.e., 295.8 mg/L and 9,666.7±942.81 mg/L, respectively. In addition, the concentration of Al, Fe, Cu, and Cr was 1,194 mg/L, 515 mg/L, 0.559 mg/L, and 0.217 mg/L, respectively. The two-compartment electrochemical reactor was separated by using Cation Exchange Membrane (CEM) and Anion Exchange Membrane (AEM), and operated in a batch system for 10 hours with an electrical current of 300 mA. The results showed that the use of CEM in electrolysis with the electrodes distances of 1 cm increased the aluminum recovery up to 66.74% with the TOC removal of 24.04% compared to the use of AEM. An electrochemical process using CEM can be suggested to obtain organic-free recovery stream containing higher recovery of alum.

5

Recovery of Alum from Surabaya Water Treatment Sludge using Electrolysis with Carbon-Silver Electrodes

Barakwan Rizkiy Amaliyah, Hardina Tyta Try, Trihadiningrum Yulinah, Bagastyo Arseto Yekti

Journal of Ecological Engineering

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2019

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Vol. 20, nr 7

126--133

EN

Untreated alum sludge from Surabaya water treatment plant (WTP), which contained high concentration of alum was directly discharged into Surabaya River. It might cause problems because of the accumulation of aluminum in the lower part of the river. Alum could be recovered from the drinking water sludge using the electrolysis method. Aims of this study were to determine the optimum pH and electrical current for electrolysis using carbon-silver electrodes to recover aluminum coagulant from the sludge, and to determine the amount of the recovered alum. The sludge was acidified prior to electrolysis. Acidification was done by adding sulfuric acid at pH 3 and 4. Polarization test was conducted at 100, 200, and 300 mA, in order to determine the optimum electrical current. The electrolysis was performed in one compartment batch recirculation reactor, using silver as cathode and carbon as anode for 10 hours. Values of pH were measured every hour. The precipitated matter in the cathode was weighed, and analysed by means of Inductively Coupled Plasma. The optimum conditions of the electrolysis were achieved at initial pH 3 and electrical current 300 mA. The electrolysis resulted in the highest precipitate of 2.6112 g in the cathode.

6

Electrodialytic Recovery of Ammonium and Phosphate Ions in Fertilizer Industry Wastewater by Using a Continuous-Flow Reactor

Hikmawati Desiana Nurul, Bagastyo Arseto Yekti, Warmadewanthi IDAA

Journal of Ecological Engineering

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2019

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Vol. 20, nr 6

255--263

EN

The wastewater stream generated from fertilizer industries generally contains high concentrations of ammonium and phosphate ions. This stream offers an opportunity for the electrodialytic process to treat and recover these concentrated nutrients before releasing them to the environment. Therefore, this study aims at evaluating the performance of a continuous-flow electrodialysis reactor for ionic recovery of ammonium and phosphate. The results show that the pH and phosphate mass loading affected the overall performance of the reactor. Magnesium was added to the recovered ammonium and phosphate with the lowest concentration of impurity ions. The molar ratio of magnesium:ammonium:phosphate at 2.5:13:1 produced 57.3% of struvite (by mass) and 42.7% of other precipitate products, i.e., most likely fluorapatite and MgF2.

7

Characterization of Alum Sludge from Surabaya Water Treatment Plant, Indonesia

Barakwan Rizkiy Amaliyah, Trihadiningrum Yulinah, Bagastyo Arseto Yekti

Journal of Ecological Engineering

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2019

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Vol. 20, nr 5

7--13

EN

A conventional water treatment plant (WTP) typically involves coagulation-flocculation processes to remove suspended particles and colloids in raw water. The process generates a large volume of alum sludge with high aluminum content, which is discharged into a river with improper treatment. The sludge may cause a potential risk to human health, and disrupt the life of river biota. The aims of this study were to determine the physical and chemical characteristics of alum sludge from Surabaya WTP, and to compare them with those of alum sludge from other plants in Indonesia and developing countries. The alum sludge sample was obtained from the Surabaya WTP in Indonesia. The results showed that the alum sludge had a pH value of 7.47, volatile solids of 12,696 mg/L, total suspended solids of 12,511 mg/L, chemical oxygen demand (COD) 9666.7 mg/L, biochemical oxygen demand (BOD) 1082.5 mg/L, and sludge volume index 114.18 mL/g. The sludge had high aluminum and iron concentrations. The aluminum content of the sludge was 1194 mg/L, iron 515 mg/L, chromium 0.217 mg/L, and copper 0.559 mg/L. Having a BOD/COD ratio of 0.1, the alum sludge contained high level of nonbiodegradable organic matter.