Solids Removal Research Articles

Contribution of ammonium oxidizing archaea and bacteria to intensive nitrification during summer in Mutsu Bay, Japan

Nitrification, in which ammonium is oxidized to nitrate via nitrite, is a regeneration process of bioavailable nitrogen. Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) carry out the ammonium oxidation. Here we measured the ammonium oxidation rates (AORs), distinguishing those of AOA (VA) and AOB (VB), for two years in Mutsu Bay, a subarctic semi-enclosed bay. Nitrate and ammonium were depleted in the upper layer in summer, but a high concentration of nitrate was observed at the bottom (below 40 m), of up to 7.8 μM with a strong vertical gradient within several meters of the seafloor. A High AOR of up to 0.17 μM d−1 were observed in the bottom waters. The AOA were responsible for most of the total AOR, but the VB exceeded the VA just above the seafloor (0.3 m) in September. Removal of the suspended solids (SS) did not change the AOA’s oxidation activity but eliminated the AOB’s. This finding suggested that AOA were free-living whereas AOB were attached to the SS’s surface. It is also suggested that the sediment was this SS’s source. When ammonia mono-oxygenase, amoA, of AOA and AOB, was quantified, the copy number of AOA-amoA was an order of magnitude higher than that of AOB-amoA throughout the study period. A significant correlation (p < 0.05) was found between the AOB-amoA copy number and VB whereas no correlation was found between the AOA-amoA copy number and VA suggesting the AOA-amoA copy number did not always represent active cells. Ammonia oxidation was occurring near the bottom waters of Mutsu Bay during the summer, and it was accompanied by a dynamic balance reflecting the difference in the AOA’s and AOB’s lifestyles, free-living and particle-associated, respectively.

Ultrafine Kaolinite Removal in Recycled Water from the Overflow of Thickener Using Electroflotation: A Novel Application of Saline Water Splitting in Mineral Processing.

The presence of ultrafine clay particles that are difficult to remove by conventional filtration creates many operational problems in mining processing systems. In this work, the removal of clay suspensions has been investigated using an electroflotation (EF) process with titanium electrodes. The results show that EF is a viable and novel alternative for removing ultrafine particles of kaolinite-type clay present in sedimentation tank overflows with low salt concentrations (<0.1 mol/L) in copper mining facilities based on the saline water splitting concept. Maximum suspended solid removal values of 91.4 and 83.2% in NaCl and KCl solutions, respectively, were obtained under the experimental conditions of the constant applied potential of 20 V/SHE, salinity concentration of 0.1 mol/L, and electroflotation time of 10 and 20 min in NaCl and KCl solutions, respectively. Furthermore, the visual evidence of particle aggregation by flocculation during the experiments indicates a synergy between EF and electrocoagulation (EC) that enhances the removal of ultrafine particles of kaolinite.

Chitosan of blood cockle shell (Anadara granosa) as a natural coagulant for removal of total suspended solids (TSS) and turbidity of well-water

Blood clam or blood cockle (Anadara granosa) is a clam species with high calcium carbonate (CaCO3) and chitin content; these compounds are commonly used in coagulation water treatment. This study examined the capacity of blood cockle shells (BCS) as an innovative natural coagulant in the form of unmodified powder (BCSP) and chitosan extracted from the shells (BCSC) to reduce TSS and turbidity of well-water. SEM and FTIR analysis were conducted to analyse the characteristics of the media. The coagulant dose, pH of the water sample, and settling time were investigated using a jar test experiment to determine the optimum condition for each experimental system. Rapid mixing (1 min at 120 rpm) was followed by slow mixing (10 min at 60 rpm), followed by settling times ranging from 10 to 30 min. The optimum settling time was 30 min, after which 76% TSS and 76% turbidity were removed using 75 mg/l of BCSP at pH 4. The tests with BCSC resulted in 80% TSS and 81% turbidity removal with 200 mg/l of BCSC at pH 5 and a settling time of 30 min. The results were compared to the performance of alum (Al2(SO4)3·18H2O), a commercial chemical coagulant. Under similar dosage (200 mg/L) and pH (= 6) conditions, alum reduced turbidity and TSS by 95% and 97%, respectively. These results indicate that blood cockle shell-based coagulant is a promising environmental-friendly material that can compete and possibly replace conventional chemical coagulants in water treatment systems.

The Leaching Behavior of Zinc Oxide in Medical Waste of Dental Clinics

Zinc Oxide is an indispensable substance in the field of dental treatment. It is used daily and intensively in all governmental and private dental clinics, leading to the disposal of very high concentrations of zinc with waste and eventually in landfill sites as a final destination for solid waste removal. This indicates the urgent need to investigate its behavior upon disposal due to the surrounding conditions. Approximately 4195 g of mixed dental waste samples were collected from (17) healthcare centers in Baghdad Al-Karkh. The leaching behavior of ZnO powder was investigated through batch reactors using makeup dental solid waste samples. The ZnO leaching was tested with 3 conditions; acidic, alkaline, and Ionic Strength (IS). The acidic condition was considered the most hazardous condition compared with basic and salinity due to the increasing tendency of ZnO to release Zn ion within waste leachate. In solutions with low pH, the dissolution of ZnO tends to produce zinc ions due to the attack of the ZnO surface by proton. In solutions of pH more than 9, the degradation of zinc oxide produces hydroxide complexes. Increasing (IS) decreased zinc concentration in leachate samples with time by promoting solids aggregation, decreasing the repulsive forces of ZnO particles, and accumulating in the bottom of reactors.

ON THE ISSUE OF SOCIAL AND ECONOMIC SECURITY OF MODERN CITIES OF UKRAINE

The article discusses the directions of social and economic security of modern cities of Ukraine. The development of an effective model of security of a modern city should use a logical basis, take into account regional development plans, directing efforts to consistently increase the human development index in the medium term. Such a model should be created taking into account all categories of the population, the nature of the activities of residents and the current state of life of citizens, etc. The number one issue for the development of modern Ukrainian cities, regardless of size, is economic development, as job creation and investment attraction are key to the healthy development of a city, regardless of its location or size. Community leaders and scholars who research this issue believe that planning, water supply, and transportation infrastructure (roads, highways, and bridges) are of great importance to their communities. The Russian-Ukrainian war set new requirements for models of social and economic security of Ukrainian cities, for city management and implementation of city policy. &#x0D; In general, they are related to the relocation of industries or the emergence of their new forms, the formation of new rules for business, the reorientation of sales markets, which fundamentally changes the understanding of the foundations of urban politics. Traditionally, the management of the city's development is mainly focused on ensuring its economic component. However, it is important to take into account the social sphere in this process by shifting the emphasis to intangible factors, updating the service sector, developing intercultural interaction, establishing relationships between business and culture. Such measures will ensure resistance to changes in economic and social spheres of the city's life, as well as focus on innovative development and the achievement of a high quality of life for every citizen. A group of issues such as emergency planning, parks and recreation areas, health care, solid waste removal, and law enforcement are of almost equal importance in the context of the post-war reconstruction of Ukrainian cities. Given the differences in individual security needs in the cities of Ukraine bordering the russian federation and the war zone and cities that have received internally displaced persons, it is necessary to promote the development of specific models of social and economic security of cities based on taking into account various directions and conditions for their implementation.

Suspended solid removal efficiency of plate settlers and tube settlers analysed by CFD modelling.

Removal of suspended solids from raw water is an essential process in water treatment plants. Conventional sedimentation tanks in water treatment plants occupy a large area and become expensive in urban areas. The use of plate settlers or tube settlers in sedimentation tanks to increase the efficiency and hence reduce the footprint of sedimentation tanks is an economical solution in water treatment. This study investigated the effectiveness of plate and tube settlers compared to conventional settlers in a water treatment plant. A three-dimensional Computational Fluid Dynamics (CFD) model was set up using ANSYS-CFX 17.2. Seven cases (a conventional settler, three plate settlers and three tube settlers) were analysed to compare the settler performances. The maximum removal efficiencies of all solid classes were approximately equal in plate and tube settlers with the same plate spacing and tube depth: around 100%, 67%, 28% and 9% for the solid classes with particle diameters of 41, 17, 9.5 and 5.0 µm, respectively. The settling efficiency remained unchanged with the increase of the plate settling area beyond 60% of the conventional settler area under the given tank and flow conditions. The tube cross-section shape does not affect the particle removal efficiency of a tube settler.

Selective removal of ultrafine suspended solids during organic pollutant degradation by a MoS2/graphene oxide sponge

Selective removal of ultrafine suspended solids during organic pollutant degradation by a MoS2/graphene oxide sponge

A comparison study of heat-assisted Fe2+/persulfate and powdered activated carbon/persulfate wastewater pre-treatment for membrane fouling alleviation

Heat/Fe2+/persulfate (PS) and heat/powdered activated carbon (PAC)/PS exhibit oxidation, coagulation, and adsorption effects, respectively. However, no studies have been conducted to discuss and compare the synergistic contribution to membrane fouling mitigation under thermal synergy. Herein, heat/Fe2+/PS and heat/PAC/PS systems were used to alleviate membrane fouling during municipal wastewater recycling in an aerobic granular sludge membrane bioreactor (AGMBR), and the effects of oxidation, coagulation, and adsorption on the membrane fouling mitigation were analyzed. The results showed that heat/Fe2+/PS and heat/PAC/PS effectively increased the filtration flux, decreased the fouling resistance, and maintained the membrane surface morphology. Compared to heat/PAC/PS, the heat/Fe2+/PS exhibited better control of membrane fouling owing to the generation of sulfate radicals and Fe3+. The non-radical effect is an important way to mitigate membrane fouling by heat/PAC/PS. Moreover, the pretreatment systems were effective in decomposition and removal of large-particle-size pollutants owing to their excellent oxidation capacity. According to the extended Derjaguin–Landau–Verwey–Overbeek theory, the heat/Fe2+/PS system had the higher energy barrier values of foulant–membrane (155.31 kT) and foulant–foulant (113.75 kT). The cake filtration and intermediate blocking models were the major mechanisms of membrane fouling, and efficient removal of chemical oxygen demand (R2>0.93) and suspended solids (R2>0.92) were beneficial to the membrane fouling mitigation. This study elucidates the differences in the mechanisms of heat/Fe2+/PS and heat/PAC/PS in mitigating AGMBR membrane fouling.

Long-term effect of free ammonia pretreatment on the semi-continuous anaerobic primary sludge digester for enhancing performance: Towards sustainable sludge treatment

Primary sludge (PS) is one of the major sludge sources for anaerobic digesters in wastewater treatment plants. Although the impact of free ammonia (FA) pretreatment on methane production from anaerobic PS digestion was previously investigated using batch biochemical methane potential tests, these tests could not fully represent the continuous/semi-continuous anaerobic digestion that is currently used in practice. This study comprehensively evaluated the impact of FA pretreatment on the performance of anaerobic PS digestion for the first time using semi-continuous systems that run for over 120 days. FA pretreatment (560 mg NH3-N/L, 24 h) improved the volatile solids (VS) removal of PS by 12.2 % from 60.5 % to 67.9 %, with a similar improvement in total chemical oxygen demand removal of 14.9 % and methane production of 16.1 %. FA pretreatment increased the biomass-specific hydrolysis rate of digesters by 23.5 %. Model-based analysis revealed that the enhanced anaerobic digestion performance may be due to both the increased apparent hydrolysis rate (increased by 26.7 %) and the enhanced degradability extent (increased by 9.5 %) of PS, caused by FA pretreatment. The dewaterability of digested sludge was enhanced by 14.0 % due to FA pretreatment, which is also supported by the reduced capillary suction time from 15.1 s to 10.9 s. Removals of Fecal Coliform and E. Coli were enhanced by 0.6 and 1.4 log Most Probable Number/g vS by FA pretreatment. This study firstly manifested that FA pretreatment is a favourable approach to improve the performance of anaerobic PS digestion with extra benefits in pathogen removal and dewaterability.

An Inexpensive, Reproducible Method to Quantify Activated Sludge Foaming Potential: Validation through Lab-Scale Studies and Year-Long Full-Scale Sampling Campaign.

Activated sludge is a conventional treatment process for biochemical oxygen demand (BOD) and total suspended solids (TSS) removal at water resource recovery facilities (WRRFs). Foaming events are a common operational issue in activated sludge and can lead to decreased treatment efficiency, maintenance issues, and potential environmental health risks. Stable foaming events are caused by biological and chemical drivers (i.e., microbes and surfactants) during the aeration process. However, foaming events are difficult to predict and quantify. We present an inexpensive and easy-to-use method that can be applied at WRRFs to quantify foaming potential. Subsequently, the method was applied over a year long full-scale study while data on microbial community composition and functional parameters associated with foaming potential were collected from activated sludge samples at South Shore Water Reclamation Facility (WRF) (Oak Creek, WI). Results from the development of the foaming potential method using linear alkylbenzene sulfonate (LAS) showed that the method was reproducible (relative standard deviation < 20%) and able to capture changes in foam inducing constituents. Using full-scale activated sludge samples, higher relative abundance values for the following genera were associated with foaming events: Zoogloea, Flavobacterium, Variovorx, and Bdellovibrio. This is the first report that Variovorx and Bdellovibrio relative abundance was correlated with foaming events in activated sludge. Furthermore, the foaming potential positively correlated (p ≤ 0.05) with soluble total nitrogen. Characterizing foaming events through frequent sampling, and monitoring of specific genera and functional parameters may allow for predictions and preemptive mitigation efforts to avoid negative consequences in the future.

Physico-chemical characteristics and biodegradability of primary effluent and particulate matter removed by microscreens.

In this study, the physical, chemical, and biological characteristics of raw wastewater were compared with the liquid and solid streams generated by a primary clarifier (PC), a rotating belt filter (RBF, 350 μm), and a drum filter (DF, 60 μm) and series (SER) combination of an RBF with a PC or a DF using pilot-scale primary treatment units. The RBF removed about 36% of the influent total suspended solids. The DF and PC yielded an influent total suspended solid removal of 47% to 55% in both individual (parallel) and SER configurations. The size fractionation and chemical characterizations of the liquid fractions indicated a significant change in the wastewater composition in both filter configurations with no variation in the biodegradability of liquid fractions. The solids recovered by RBF had a higher total solids (TS) concentration and a higher volatile solids (VS) content (0.92 g VS/g TS) than that of DF and PC treatments (0.58 to 0.84 g VS/g TS). DF and PC sludge demonstrated a higher biodegradability rate (k1 ; 0.11 d-1 < k1 < 0.20 d-1 ) than solids recovered by RBF (0.09 d-1 ). The retained solids in the SER configuration demonstrated a significantly lower theoretical biochemical methane potential than the parallel configuration, likely due to the presence of smaller particles with a significantly higher ratio of particulate chemical oxygen demand over volatile suspended solids (1.86 to 2.40 g chemical oxygen demand/g volatile suspended solids). These results indicated that the physical, chemical, and biological characteristics of liquid and solids from different filter configurations are required to determine design criteria to upgrade or retrofit water resource recovery facilities using an RBF or a DF. PRACTITIONER POINTS: A rotating belt filter (RBF) removed less solids than a drum filter (DF) or a primary clarifier (PC). A series configuration of an RBF with either a DF or PC resulted in an effluent with a lower proportion of slowly biodegradable organic matter than in a parallel configuration. Solids from an RBF, a DF, or a PC had similar theoretical biochemical methane potential.

Staircase Wetlands for the Treatment of Greywater and the Effect of Greywater on Soil Microbes

Fresh water is an increasingly scarce resource in both urban and rural development. As a response to this challenge, non-potable water reuse is on the rise. This research explored a potential off-grid system for water purification, consisting of a staircase wetland with terracotta pot plants working as a filter for greywater. This study further investigated the physicochemical properties of greywater and the soil before and after wetland purification. The removal of total suspended solids, total coliforms, fecal coliforms, etc., was always between 90 and 99%. Results show that the filtered water satisfied all requirements for water reuse, e.g., a pH of 7–7.5 and a turbidity &lt; 5 NTU. This research then uniquely investigated the effect of greywater on soil microbes and soil biomass using soil DNA extraction and the tea bag index testing method. The filtered greywater absorbed by soil decomposed the soil faster (66% for green tea) and stabilized it better compared to tap-water-absorbed soil or unfiltered greywater. DNA generation sequencing revealed no significant differences in alpha diversity between the control and treatment samples. The beta diversity differences were significant. This nature-based solution can lead to reduced loads on the sewage system, resulting in less wastewater generation.

Bioproducts from anaerobic co-digestion of organic fraction of municipal solid waste: substrate mixing ratios for power, heat and digestate potential assessment as support for scale-up

Thisresearch investigated the use offood waste - FW and garden waste - GWas substrates for producing thermic and electric energy on a labbioreactor. A mesophilic continuous stirred-tank reactor (CSTR) was used to support the operational planning of a pilot-scale Plant, consisting indigesters of 430 m3. The bioreactor was operated during 284 days under organic loading ratesfrom1.4 to 3.9 kg VS/m3. d and using different FW:GW ratios to simulate cities routine. The operation of the CSTR showed pH stability, high efficiency of solids removal (74.8 to 97.3%), and a maximum methane yield of 0.51 L CH4/gVS. Considering the most efficient scenario, it was calculated an electric and thermic energy potential of 183 kWheand 554 kWhtper ton of fresh matter. Regarding to the energy yield, up to 18.5 kJ/g VS was estimated. The composite sample of the digestate revealed nitrogen, sodium and potassium as major compounds (1530, 1350, and 1300 mg/L, respectively),and heavy metals under safe limits.As future scope, the presented energy simulations through metane-based energy production system may serve as a boosting step for Biogas Plants, providing valuable references for real scale applications from different proportions of organic urban residues.

Biochemical Treatment of Poultry Manure and Buffalo Dung to Enhance Methane Generation Using Lab-Scale An-Aerobic Digester: Effect of Mesophillic Condition on Methane Generation

Poultry industry is one of the important growing poultry Industry of Pakistan, the pollution produced due to this causing serious environmental threats such as aquatic life disturbance, air, water and land pollution, pathogen contamination, bad odor, soil contamination and ammonia evaporation. This research study deals with utilization of poultry manure (PM) and buffalo dung (BD) for methane generation and enhance the generation through optimization of substrate mixing ratio and observe the effect of mesophillic condition on methane generation. The PM and BD were biochemically treated by anaerobic digestion. The mixing of P.M and B.D were carried out in ratio 3/1, 1/3 and 1/1 in 500 ml glass bottles acting as bio-reactor. The PM and BD alone were also used in different bioreactor. All the digesters have retention time of 65 days and operated at temperature of 37oC. Each digester distilled water and substrates were used in 1:1 ratio. All the digesters were operated by batch wise process. The generation of biogas from experimental work was maximum from 1:3 of P.M and B.D yield 561 Nml/gm.vs. The methane generation was also maximum in digester containing one part of P.M and three part of buffalo dung the methane generation was also maximum 66 %containing 32 % carbon dioxide. From this study we conclude that biochemical treatment of substrates mixed together in different ratios produces large quantity, quality, higher biodegradability and effective volatile solid removal from substrate.

Effectiveness of the tropical plants Rhynchospora corymbosa and Coix lacryma-jobi in vertical flow constructed wetlands for municipal primary sewage effluent treatment

The performance of two tropical plants, Rhynchospora corymbosa L. (RC) and Coix lacryma-jobi, L (CL) in treatment of primary sewage effluent in lab-scale vertical-flow constructed wetlands (VFCW) along with no plant control wetland was investigated. A batch-flow VFCWs were operated under batch fill and drain hydraulic loading system with hydraulic retention times (HRT) of 0.5, 1, and 2 days and fill rate of 8 L/day. Removal of solids, organics, nutrients, and pathogens were monitored. The volumetric contaminant removal rates were best described by 1st order kinetics except for ammonia and phosphate, which was best described by Stover-Kincannon kinetics. Influent TSS, PO4 3−, COD, BOD5, and total coliform concentration were low but high in NH4 + concentration. CL was better in nutrient removal as HRT increases compared to RC. RC was more efficient at TSS, turbidity, and organics removal. Pathogen removal was independent of plant type but HRT. Solids and organic removal were lower in CL planted CWs due to preferential flow paths created by their bulky root. CL planted CWs removed more nutrients followed by RC planted CWs and then no-plant control CWs. The results of these tests demonstrate that both CL and RC are suitable for the treatment of municipal wastewater in VFCW system.

Применение ферментов при выработке фруктового сока: обзор

Enzymatic treatment is a common method of fruit juice production that facilitates juice extraction from plant cells. The choice of enzyme depends on the fruit composition. Pectinase and cellulase are the most popular enzymes while amylase remains less wide-spread. For some raw materials, enzymatic procedures are more efficient than mechanical comminution or thermal processing. The fruit juice industry uses enzymes for streamlining. Enzymes maximize juice extraction from raw materials and improve such processes as pressing, solid settling, and solid removal. Juices that underwent enzymatic treatment are clear and, as a result, more aesthetically appealing to consumers.&#x0D; The review covered the most recent and influential publications on the enzyme treatment of fruit juices (2000–2021). The list of enzymes included pectinase, cellulase, and amylase. The research included the factors that affect the juice fermentation process, i.e., hydromodule, enzyme concentration, incubation time, temperature, and enzyme combination. The methods included data extraction, data analysis, and data compilation, as well as literature search and screening.&#x0D; The review focuses on the effects that individual parameters have on specific responses, e.g., yield, viscosity, total soluble solids, acidity, turbidity, clarity, pigment concentration, phenolic content, color, and solids. A greater enzyme concentration, incubation time, and temperature decrease the viscosity of juice and turbidity but cause color changes. If used in different combinations and at different concentrations, enzymes boost the production of bael pulp, banana, sapodilla, durian, pawpaw, grape, white pitaya, and water melon juices. A longer incubation period improves the production of bael pulp, citron, date, and pawpaw juices. However, higher incubation temperatures seem to have no positive effect on the juice yield. Cellulases, pectinases, amylases, and their combinations are able to produce more fruit juice of higher quality with a more favorable time-temperature combination of incubation.&#x0D; The optimal enzyme concentration, incubation time, and temperature can increase the juice yield. Therefore, enzymatic treatment is an effective method that ensures favorable properties of the finished product.

Based on Improved NSGA-II Algorithm for Solving Time-Dependent Green Vehicle Routing Problem of Urban Waste Removal with the Consideration of Traffic Congestion: A Case Study in China

The dense population and the large amount of domestic waste generated make it difficult to determine the best route and departure time for waste removal trucks in a city. Aiming at the problems of municipal solid waste (MSW) removal and transportation not in time, high collection and transportation costs and high carbon emissions, this paper studies the vehicle routing problem of municipal solid waste removal under the influence of time-dependent travel time, traffic congestion and carbon emissions. In this paper, a dual objective model with the lowest total economic cost and the highest garbage removal efficiency is established, and a DCD-DE-NSGAII algorithm based on Dynamic Crowding Distance and Differential Evolution is designed to improve the search ability, improve the convergence speed and increase the diversity of the optimal solution set. The results show that: according to the actual situation of garbage collection and transportation, the method can scientifically plan the garbage collection and transportation route, give a reasonable garbage collection scheme and departure time, and effectively avoid traffic congestion time; Through algorithm comparison, the algorithm and model proposed in this paper can reduce collection and transportation costs, improve transportation efficiency and reduce environmental pollution.

Effects of Different Materials on Biogas Production during Anaerobic Digestion of Food Waste

One of the best methods for turning different types of biomass into clean energy is anaerobic digestion (AD). Organic and inorganic additives may be employed in the AD process to increase biogas output. It has been demonstrated that inorganic additives, such as micronutrients, can improve the efficiency of biogas producing reactors. These trace items can be introduced to the AD process as powders. The use of metal oxides in engineering and environmental research has become more popular. This study focuses on the role of TiO2 and ZnO/Ag powders on anaerobic digestion. Food waste studies on biochemical methane potential were performed with and without TiO2 and ZnO/Ag powders to examine their impact on AD. All powders are grown through the hydrothermal procedure, which has proved to be environmentally friendly and low in cost, presenting the capability to simply control the materials’ characteristics at mild temperatures. The addition of ZnO/Ag and TiO2 improved the biogas cumulative yield by 12 and 44%, respectively, compared to the control reactor. In addition, volatile solids (VS) removal efficiency increased by 5.7% in the food wastes (FW) and TiO2 reactor, while total chemical oxygen demand (TCOD) removal efficiency increased by 22% after the addition of ZnO/Ag.

Chemical Oxygen Demand (COD) and Total Suspended Solid (TSS) Removal from Rubber Wastewater Factory Using Electrocoagulation Technique

Rubber industrial wastewater is obtained during washing, shredding, grinding, crumbbing, drying, and pressing bokar. The wastewater produced can be an environmental pollutant because it contains relatively large amounts of organic matter. One alternative to treating rubber wastewater is to use the electrocoagulation process, which is a combination of the coagulation and electrolysis processes. This electrocoagulation process has several advantages in the form of simple equipment, short time, produces odorless wastewater, does not require large areas of land, and can remove various contaminants in water. In this study, rubber wastewater was treated by electrocoagulation using a batch system with variations in the contact time used, namely 20, 40, 60, 80, and 100 minutes. This type of research is experimental research, and descriptive analysis is carried out. Rubber wastewater is physically gray-black before treatment and chemically contains large organic matter. The results of this study showed that the content of chemical oxygen demand (COD) and total suspended solids (TSS) before processing had values of 691 mg/L and 317 mg/L. Optimum conditions for the elimination of COD and TSS contents were achieved within 80 minutes with the percentage of elimination being 89% and 85%.

Optimization and Evaluation for the Capacitive Deionization Process of Wastewater Reuse in Combined Cycle Power Plants

Combined cycle power plants (CCPPs) use large amounts of water withdrawn from nearby rivers and generate wastewater containing ions and pollutants. Despite the need for wastewater reclamation, few technologies can successfully convert the wastewater into make-up water for CCPPs. Therefore, this study aimed to apply capacitive deionization (CDI) for wastewater reclamation in CCPPs. Using a bench-scale experimental unit, which included ion exchange membranes and carbon electrodes, response surface methodology (RSM) was used to optimize the operating conditions of the CDI process to increase the total dissolved solids (TDS) removal and product water ratio. The optimal conditions were found to be a voltage of 1.5 V, a flow rate of 15 mL/min, and an adsorption/desorption ratio of 1:0.8. The changes in CDI performance with time were also studied, and the foulants on the membranes, spacers, and electrodes were examined to understand the fouling mechanism. The TDS removal decreased from 93.65% to 55.70% after 10 days of operation due to the deposition of scale and organic matter. After chemical cleaning, the TDS removal rate recovered to 93.02%, which is close to the initial condition.