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)

Development of an optimization model for phosphorus recovery in wastewater treatment plants

The current limited supply of phosphate rock ores poses a threat to the global food security since 95% of the phosphorus is utilized for food production. One sustainable alternative is to recover nutrients (phosphorus and nitrogen) from nutrient-rich sources such as wastewater and sludge. The problem lies on the selection of technologies while considering the total costs of a wastewater treatment plant (WWTP) since high recovery entails high WWTP costs. The study develops a lexicographic ε-constraint optimization model with total annualized cost (TAC) and overall phosphorus recovery as objective functions. The model can aid the decision-makers in determining possible combination of technologies and the corresponding trade-offs (high TAC and low TP recovery, and vice versa). Furthermore, the model can provide insights on the impact of different variables to the overall cost and TP recovery for different sink applications. Its capability was demonstrated using two case studies: one for wastewater treatment and one for phosphorus recovery from sludge. Literature review is carried out to search for available techno-economic data. Then, the proposed model was subject to topological, logical, and structural constraints. The 1st case study utilized Mixed Integer Quadratic Program (MIQP) while the 2nd case study used Mixed Integer Non-Linear Program (MINLP) due to the variable outgoing contaminant concentrations. Lexicographic ε-constraint method produced dominant solutions which is attributed to the use of constant flowrate values and variable technology efficiencies in determining the TAC and overall phosphorus efficiency. Lastly, sensitivity analysis provided insights on the impact of varying influent characteristics and land area requirements. Challenges include limited techno-economic data for various technologies and generation of dominating solutions. Therefore, recommendations for the study are as follows: improve the techno-economic data of the technology alternatives, consider evaluating the TAC and P-recovery for large-scale WWTPs (\u3e100 m3/d), and improve the model such that it would provide non-dominating solutions

Storage Stability and Disinfection Performance on <i>Escherichia coli</i> of Electrolyzed Seawater

The study investigated the effect of storage conditions on the stability of electrolyzed seawater (ESW)&#8217;s physicochemical properties (pH, oxidation-reduction potential (ORP), and free chlorine (FC) concentration), and bactericidal efficiency on the fecal coliform Escherichia coli for 30 days. Preliminary experiments were conducted to determine the optimal current and electrolysis time. Two batches of 2750 mL filtered seawater were electrolyzed using 50 mm &#215; 192 mm platinum&#8722;titanium mesh electrodes at a current of 1.5 A for 20 min. One hundred milliliters of electrolyzed solution was transferred into each amber glass and high-density polyethylene (HDPE) bottles. The bottles were stored in a dark area at ambient temperature. The results showed an increase in pH and a decrease in ORP and FC concentration through time. Hypochlorous acid remained as the dominant component since the pH levels of the solutions remained below 7.5. FC decay was investigated using Chick&#8217;s Law. It was determined that the decay in HDPE bottles (k = &#8722;0.066 day&#8722;1) was faster compared to amber glass bottles (k = &#8722;0.046 day&#8722;1). Nonetheless, HDPE bottles could still be used as an alternative container for 30 days only due to observed instability beyond 30 days. ESW remained effective since no surviving population of E. coli was observed throughout the experimentation

Storage stability and disinfection performance on Escherichia coli of electrolyzed seawater

© 2019 by the authors. The study investigated the effect of storage conditions on the stability of electrolyzed seawater (ESW)\u27s physicochemical properties (pH, oxidation-reduction potential (ORP), and free chlorine (FC) concentration), and bactericidal efficiency on the fecal coliform Escherichia coli for 30 days. Preliminary experiments were conducted to determine the optimal current and electrolysis time. Two batches of 2750 mL filtered seawater were electrolyzed using 50mm × 192mmplatinum-titanium mesh electrodes at a current of 1.5 A for 20 min. One hundred milliliters of electrolyzed solution was transferred into each amber glass and high-density polyethylene (HDPE) bottles. The bottles were stored in a dark area at ambient temperature. The results showed an increase in pH and a decrease in ORP and FC concentration through time. Hypochlorous acid remained as the dominant component since the pH levels of the solutions remained below 7.5. FC decay was investigated using Chick\u27s Law. It was determined that the decay in HDPE bottles (k = -0.066 day-1) was faster compared to amber glass bottles (k = -0.046 day-1). Nonetheless, HDPE bottles could still be used as an alternative container for 30 days only due to observed instability beyond 30 days. ESW remained effective since no surviving population of E. coli was observed throughout the experimentation

Performance of stored electrolyzed seawater for disinfection of Pseudomonas aeruginosa

Electrolysis of seawater has the ability to produce free chlorine (FC), sodium hypochlorite (NaClO), hypochlorous acid (HOCl) and other oxidants which enable it to kill pathogens making it a viable disinfectant. However, the stability of this disinfectant is somewhat unpredictable during storage. This study determined the effects of storage time on the stability of electrolyzed seawater (ESW) in terms of its physicochemical properties, specifically pH, oxidation-reduction potential (ORP), and free chlorine concentration (FCC) for 83 days and evaluated its disinfection performance on Pseudomonas aeruginosa. The effect of dilution in the disinfection was also investigated at ESW to water ratio of 1:0, 1:1, and 3:6. Pre-filtered seawater was electrolyzed at 1.5 A for 20 minutes using platinum-coated titanium mesh electrodes. The ESW was transferred to opaque high-density polyethylene (HDPE) bottles stored at ambient temperature without direct exposure to sunlight. The physicochemical properties of ESW at different storage times were determined, and its disinfection capability against P. aeruginosa was evaluated. This study has made use of two trials for the physicochemical test due to two different batches of seawater were taken. pH was found to increase over time, having a range of 6.32 to 7.705. The ORP and FCC, on the other hand, decreased over time. In accordance with the literature found, the pH ranges show that hypochlorous acid is the main driver of disinfection. Complete disinfection of ESW at 3:6 dilution was observed until 48 days of storage, while the 1:0 dilution was until 83 days and 1:1 dilution was until 51 days. FC decay (k=-0.1449 day-1 and k=-0.0544 day-1) was determined using Chick\u27s Law. Even at different dilution levels, ESW still proved its bactericidal efficacy in this research. © 2020 IOP Publishing Ltd

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)

Phosphorus recovery from septage treatment plant sludge by struvite formation with alkaline hydrolysis as pre-treatment

Insufficiency of phosphorus due to the limited availability of phosphate rocks is predicted within the next decades. Phosphorus recovery from wastewater sludge was found to be one of the possible alternative sources of phosphorus. Moreover, stringent effluent standards, including that of phosphorus levels, have been newly implemented in the Philippines. Due to these factors, phosphorus recovery from wastewater in Philippine settings was deemed as an important topic to be further studied. In this paper, the feasibility of recovering phosphorus from septage sludge in Metro Manila by the precipitation of struvite crystals was studied. Septage sludge is seen as one of the potential sources and was characterized in terms of the concentration of Mg2+, Ca2+, NH4+ and PO4-3 ions. In the lab-scale experiments conducted, alkaline hydrolysis using sodium hydroxide was performed as a sludge pretreatment before the precipitation proper. Alkaline hydrolysis was done to release the remaining PO4-3 ions from the solids present in the sludge, thereby promoting precipitation after hydrolysis without the need for additional phosphate source. Furthermore, alkaline hydrolysis can effectively release phosphorus without inducing the dissolution of interfering ions such as Ca2+ and other heavy metals. Results show that PO4-3 ions increased by 267.37 mg/L and the total amount of phosphate ions increased from 17.05% to 46.88%, showing the effectivity of the hydrolysis. For the precipitation of struvite, three parameters were controlled: pH, residence time, and Mg:P ratio. After precipitation, the phosphorus recovery efficiency for the runs were each evaluated and analyzed in order to determine the effects of the parameters on phosphorus recovery. The precipitate of the run with the highest phosphorus recovery obtained was then evaluated using XRD analysis. It was found that the sample with the highest phosphorus recovery is 53.12%, which was achieved at pH 9, a residence time of 1 hour, and an Mg:P ratio of 1.5:1. Therefore, it can be concluded that precipitation subjected at pH 9 has the highest potential for higher phosphorus recovery. Further, the residence time has a minimal effect on phosphorus recovery and higher phosphorus recovery can be achieved at a higher Mg:P ratio with increasing potential for struvite recovery. © 2020 IOP Publishing Ltd