Performance evaluation and upgrade options for existing sequencing batch reactor for nutrient removal

Assessment and upgrade of existing sewage treatment plants (STPs) are necessary due to the revision of the existing effluent regulations which now monitors nutrients including ammonia, nitrate and phosphates. The aim of this study is the performance evaluation of four sequencing batch reactor (SBR) type of STP based on the following parameters: biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), nitrates, ammonia, phosphates and pH; and their potential upgrade based on the revised regulations stated in DAO 2016-08. Four sequencing batch reactor (SBR) type of STP were assessed for 12 weeks for this study. Results showed noncompliance with nutrient levels, thus upgrade is necessary. Analytical Hierarchy Process (AHP), a Multi-Criteria-Analysis (MCA) tool, was used to select the best option for upgrade among options that include (1) additional SBR tank, (2) diverting wastewater to another treatment facility, and (3) converting the SBR into membrane bioreactor (MBR). Considering the criterion for upgrade, option 2 was the most preferred decision followed by option 1 then option 3

Copper uptake potential of Philippine giant bamboo (Dendrocalamus asper) under varied initial copper concentration, water hardness and pH

Copper is a commonly used metal in construction, engineering, agriculture and water treatment. Consequently, increased copper concentrations resulting in adverse environmental effects is inevitable. Phytoremediation using Dendrocalamus asper or Philippine giant bamboo (PGB) is a viable option for treatment of copper-contaminated media, but their copper uptake potential remains largely unexplored. As such, the copper uptake of PGB was evaluated under varying environmental conditions, namely initial copper concentration, water hardness and pH.Six-month old propagules were planted in artificially contaminated water in order to determine the copper uptake after 16 days of treatment. Using a Box-Behnken design of experiment, it was found that both initial copper concentration and pH have significant and proportional effects on copper uptake. However, due to possible speciation and/or competition, the optimum copper uptake occurred at 20 ppm Cu and pH 5 (as opposed to 7). A mathematical equation, bearing an R2 = 0.7097, was constructed as a possible model for copper uptake of PGB to understand when PGB phytoremediation is most effective. At copper concentrations lower than 3.81 ppm, higher pH is beneficial to copper uptake and vice versa. Overall, phytoremediation using D. asper or PGB is effective especially at low pH and elevated copper concentrations

Acetylation of Nata de coco (bacterial cellulose) and membrane formation

Nata de coco (NDC), a bacterial cellulose formed by Acetobacter xylinum, was utilized to fabricate a membrane via acetylation and phase inversion methods. The NDC was activated and dissolved in N,N-Dimethylacetamide (DMAc) with lithium chloride (LiCl) at varying amounts of NDC, LiCl/DMAc ratio, activation temperature, and dissolution temperature. Acetylation was done by adding acetic anhydride (in a mass ratio of 1:12 NDC-anhydride) to NDC-DMAc/LiCl solution at a dissolution temperature of 110 °C for 3 hours. The modified-NDC was recovered via precipitation in methanol. The modified-NDC was washed with deionized water then freeze-dried. Modification was verified by determining the degree of substitution (DS) using titration and FTIR analysis. It was observed that the modification could be carried out at an NDC/DMAc (w/v) ratio of 1:75 at 120 °C for 1 hour, and addition of 8% (w/v) LiCl catalyst at 110 °C for 20 minutes. The DS of the modified-NDC was observed in the range of 2.84 – 3.69, which indicates a successful modification. This was further verified by the FTIR results. Membrane fabrication was carried out using the modified-NDC via immersion-precipitation and solvent evaporation methods. A successful membrane formation was observed using solvent evaporation

Phosphorus recovery from wastewater and sludge

Wastewater and sludge are potential resource of phosphorus (P) for fertilizer production. One method of recovering phosphorus is via chemical precipitation. In the study, phosphorus was recovered from wastewater and sludge. First, hydrolysis was carried out to release the phosphorus in the sludge by the addition of 1.0M acid (sulfuric acid) or base (sodium hydroxide) solution mixed for three hours at 200 rpm. The hydrolyzed sludge was filtered, and the pH of the solution was adjusted to 9.0. Precipitation for both wastewater and hydrolyzed sludge solution was carried out using magnesium chloride hexahydrate (MgCl2•6H2O) and ammonium chloride (NH4Cl). The mixture was stirred for an hour for crystallization. Precipitates were allowed to settle for 24 hours before it was filtered and dried in an oven at 55-58oC for 24 hours. The dried sample was grinded and characterized using Fourier transform infrared spectroscopy (FTIR), x-ray fluorenscence (XRF), and scanning electron microscope with energy-dispersive x-ray spectroscopy(SEM-EDX)

Investigation on mixture design of one-part geopolymer from fly ash and water treatment sludge

This study presents a one-part geopolymer system from coal fly ash and water treatment sludge. Geopolymer is typically produced from two parts namely the aluminosilicate solids, which is typically sourced out from industrial by-product, and an alkali activator solution which reacts with aluminosilicate solids to form an inorganic polymeric network. For a one-part geopolymer system, the solid binder with activators will just be added with water to address the drawback of corrosive and viscous alkali activator solution. Formulation of the proportion of geopolymer precursors with the two solid alkali activators namely sodium hydroxide and sodium aluminate was conducted using statistical mixture design. Effects of each components as well as interactions between them were evaluated by step-wise regression analysis. It was found that high alkali content decreased the compressive strength of binder. Meanwhile, the incorporation of sludge in this system helps reduce the unit weight of samples. Multiple response surface analysis that maximized compressive strength and minimized unit weight resulted in the optimal combination of 18.9% sludge, 76.1% fly ash and 5.0% NaOH

Investigation on mixture design of one-part geopolymer from fly ash and water treatment sludge

This study presents a one-part geopolymer system from coal fly ash and water treatment sludge. Geopolymer is typically produced from two parts namely the aluminosilicate solids, which is typically sourced out from industrial by-product, and an alkali activator solution which reacts with aluminosilicate solids to form an inorganic polymeric network. For a one-part geopolymer system, the solid binder with activators will just be added with water to address the drawback of corrosive and viscous alkali activator solution. Formulation of the proportion of geopolymer precursors with the two solid alkali activators namely sodium hydroxide and sodium aluminate was conducted using statistical mixture design. Effects of each components as well as interactions between them were evaluated by step-wise regression analysis. It was found that high alkali content decreased the compressive strength of binder. Meanwhile, the incorporation of sludge in this system helps reduce the unit weight of samples. Multiple response surface analysis that maximized compressive strength and minimized unit weight resulted in the optimal combination of 18.9% sludge, 76.1% fly ash and 5.0% NaOH

Investigation on mixture design of one-part geopolymer from fly ash and water treatment sludge

This study presents a one-part geopolymer system from coal fly ash and water treatment sludge. Geopolymer is typically produced from two parts namely the aluminosilicate solids, which is typically sourced out from industrial by-product, and an alkali activator solution which reacts with aluminosilicate solids to form an inorganic polymeric network. For a one-part geopolymer system, the solid binder with activators will just be added with water to address the drawback of corrosive and viscous alkali activator solution. Formulation of the proportion of geopolymer precursors with the two solid alkali activators namely sodium hydroxide and sodium aluminate was conducted using statistical mixture design. Effects of each components as well as interactions between them were evaluated by step-wise regression analysis. It was found that high alkali content decreased the compressive strength of binder. Meanwhile, the incorporation of sludge in this system helps reduce the unit weight of samples. Multiple response surface analysis that maximized compressive strength and minimized unit weight resulted in the optimal combination of 18.9% sludge, 76.1% fly ash and 5.0% NaOH. © The Authors, published by EDP Sciences, 2018

Characteristics and Performance of PTU-Cu Composite Membrane Fabricated through Simultaneous Complexation and Non-Solvent Induced Phase Separation

This study aims to integrate copper (Cu) during membrane formation by a facile simultaneous phase separation process to alleviate biofouling and improve membrane performance. Polythiourea (PTU) polymer synthesized through condensation polymerization of 4,4-oxydianiline and p-phenylene diisothiocyanate in dimethyl sulfoxide was used in the preparation of dope solution. By incorporating different concentrations of cupric acetate in the non-solvent bath, both non-solvent induced phase separation and complexation induced phase separation occur instantaneously. Scanning electron microscopy—energy dispersive X-ray, fourier-transform infrared spectroscopy and time-of-flight secondary ion mass spectroscopy analysis accompanied by color change of the membrane surfaces—confirms the interaction of the polymer with Cu. Interaction of Cu at the interface during membrane formation results in a decrease in contact angle from 2 to 10° and a decrease in surface roughness from 30% to 52% as measured by atomic force microscope analysis. Pure water flux of PTU-Cu membrane increased by a factor of 3 to 17 relative to pristine PTU membrane. Both the pristine PTU and PTU-Cu membrane showed antibacterial characteristics against E. coli

Multi-criterion decision making for selecting municipal wastewater treatment technology in Metro Manila Philippines

The Philippines aims to increase the coverage of areas with wastewater treatment technologies to provide sustainable wastewater management solution particularly in its most populated area, Metro Manila, the capital of the Philippines. This involves selection of appropriate wastewater treatment technology that would minimize the discharge of untreated wastewater into bodies of water. The selection of the appropriate technology requires the assessment and evaluation of multiple criteria which may be qualitative and/or quantitative in nature. This study thus proposes a decision framework based on Analytic Hierarchy Process (AHP) to structure the selection problem systematically and to conduct the selection in a more transparent and rational manner. It also allows the decision-maker to quantify his value judgment through pairwise comparisons between criteria and between alternatives. The methodology is demonstrated utilizing a case study on the comparison of wastewater treatment options for municipal wastewater. This paper considered three secondary treatment technologies, namely, Conventional Activated Sludge (CAS), Sequencing Batch Reactor (SBR) and Membrane Bioreactor (MBR). These technologies were then evaluated using 4 criteria: technical aspect, environmental aspect, cost, and ease-to-upgrade. Among the four criteria considered, the technical and ease-to-upgrade criteria are based on the subjective evaluation of a domain expert in the wastewater treatment technology. The two other criteria are based on quantitative values obtained from literature and technology suppliers. The results showed that CAS is the most preferred option after incorporating the value judgments of decision maker

Optimal selection of desalination systems using fuzzy AHP and grey relational analysis

Water scarcity is an alarming global problem for a growing population with depleting sources of fresh water. Desalination is thus becoming an important solution for water management to address such looming shortage of the municipal water supply. At present, several technologies dominate the desalination industry which can be categorized either as a thermal process such as multi-stage flash distillation or a membrane process such as that of reverse osmosis. New desalination systems are also being developed to make the process more cost-effective and energy efficient. Hence, this work proposes a systematic approach for optimal selection of desalination systems using fuzzy analytic hierarchy process (FAHP) and grey relational analysis (GRA). Fuzzy AHP addresses the vagueness involve in the trade-off of the criteria or attributes used in evaluating the alternatives. On the other hand, the GRA solves the multiple criteria decision problem by aggregating the entire range of performance attribute values for every alternative into a single score in spite of incomplete information. An illustrative case study was presented wherein five desalination systems namely reverse osmosis (RO), combined reverse osmosis and forward osmosis (RO-FO), electrodialysis (ED), multi-stage flash distillation (MSF), and combined forward osmosis and membrane distillation (FO-MD) were evaluated. These desalination systems were compared to each other with respect to energy requirement, land footprint, system efficiency, economic viability, and maturity of technology. Sensitivity analysis was also done to determine the robustness of the modeling results from the variation of weights of the criteria. © 2016, AIDIC Servizi S.r.l