Death due to diseases from poor sanitation is a serious global issue and it has become one of the priorities of the United Nations' Sustainable Development Goals (i.e., SDG6). This SDG6 aims to provide adequate improved sanitation facilities to over 2.3 billion people around the world who have no or limited access to sanitation, wherein more than two-thirds of these un-served people live in rural areas. One of the strategies for addressing this global issue is through emerging sustainable sanitation technologies such as the Eco-Toilet System (ETS), which uses small amounts of water or is even waterless and recovers nutrients from human waste thereby promoting water-energy conservation, improved sanitation and supplement nutrients essential to plant growth. Social acceptance, however, remains a key barrier in deploying the ETS. A social perception study on the use of the ETS was conducted in a rural community in Mulanay, Philippines. The researchers analyzed the proposed combined technology acceptance model and theory of planned behavior (C-TAM-TPB) using multiple linear regression and the Mann-Whitney U-test to evaluate the perceptions and attitudes of a rural community towards the use of the ETS. The results showed that more than 50% of the respondents are aware of the nutrient value of human excreta and believe that it is usable as fertilizer; however, less than 25% prefer to utilize it for food production. Results also indicate that the behavior of the users is driven by their attitude (β = 0.420, p-value < 0.010). Moreover, the Mann-Whitney U-test results revealed that people who are knowledgeable of the nutrient value of human excreta and are willing to collect them have more positive attitude towards the ETS.

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The Integrated Water System (IWS) offers alternative water and sanitation services that can potentially benefit rural communities experiencing water scarcity. The IWS described in this study comprises three systems: The Rainwater Harvesting System (RWHS), Water Treatment System (WTS), and Eco-Toilet System (ETS). RWHS and WTS make use of rainwater, which can be utilized for several domestic uses, especially during wet season. ETS has several benefits to users including promotion of environmental and public health, as well as food security. Despite the potential benefits of the IWS components, the perceived acceptance of its users threatens the success of its implementation. This study focuses on determining the significant factors that can influence the social acceptance of IWS in the Municipality of Mulanay, Quezon Province, Philippines. This study considers behavioral intention as an indicator of social acceptance of the IWS components. The framework of this study is based on the combined technology acceptance model and theory of planned behavior (C-TAM-TPB) concept. C-TAM-TPB was analyzed using Partial Least Square–Structural Equation Modeling (PLS–SEM). The result of the C-TAM-TPB evaluation reveals that the user’s attitude towards use (ATU), including its significant predictors, can promote behavioral intention towards use of the IWS components. This study can further improve the development of IWS projects.

This paper proposes a decision model built on a hierarchical network for optimal selection of biological nutrient removal systems (BNR) in wastewater treatment plants. BNR is an important component of a sustainable wastewater management wherein resource recovery from wastewater becomes an integral part of the municipal wastewater treatment plants (WTP). However, selection of the most appropriate technology or systems requires a multiple criteria analysis. This study focuses on the following criteria namely 1) Economic aspect; 2) Technical aspect; 3) Environmental Aspect; and 4) Space Requirement. The following alternatives were then evaluated: 1) 3 Stage Pho-redox (A2O); 2) 5 Stage Bardenpho (5BP); 3) University of Cape Town (UCT); 4) Virginia Initiative Plant; 5) Sequencing Batch Reactor (SBR); 6) Membrane Bioreactor (MBR). A fuzzy ANP approach with Monte Carlo simulation was used to derive the overall priorities of these alternatives. This decision modelling approach addresses the uncertainty and complexity involved in the selection of appropriate BNR in Metro Manila’s WTP.

The adverse environmental impact caused by eutrophication has recently prompted the Philippine government to issue stringent regulatory standards for wastewater effluent quality. The involved stakeholders and industries are assessing the integration of biological nutrient removal (BNR) technologies in the current sewage treatment plant (STP) scenario. Moreover, efforts are being done to utilize wastewater as a resource such us recovery of nutrients as struvite fertilizer from the wastewater sludge. Since BNR and nutrient recovery systems are not yet integrated in STPs, the magnitude of the environmental impacts are yet to be evaluated in the Philippine setting. This study covers the holistic evaluation of the overall environmental performance scores of the following scenarios using a consequential Life Cycle Assessment (LCA) framework integrated with Analytic Hierarchy Process (AHP) in the context of Water-Energy-Food Nexus: 1) current STP scenario; 2) BNR technology; and 3) nutrient recovery system. The environmental impact assessment was done using IMPACT 2002+ methodology in terms of the following impact indicators: human health, ecosystem quality, climate change, resources, aquatic acidification, and aquatic eutrophication. Value judgments from relevant stakeholders were elicited to rank the relative importance of the impact indicators in the evaluation of the overall environmental performance score. The LCA-AHP results show that the integration of a nutrient recovery system is the most preferred scenario. Sensitivity analysis was also done to evaluate the effects of changes in diet and utilization of alternative energy.

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).

The current effluent standards emphasize on the removal of nutrients from sewage, and one solution is for establishments to install biological nutrient removal (BNR) technologies. However, there are several factors to be considered in installing or upgrading the technologies. Hence, the study utilizes two multi-criteria decision analysis (MCDA) tools to determine the important attributes and the optimal technology from the perspective of the academe, regulatory agency, and industry. Calibrated fuzzy analytical hierarchy process (FAHP) calculates the relative importance of the three criteria (implementability, financial, and socio-environmental) and twelve sub-criteria. On the other hand, the grey relational analysis is used to calculate the performance of the four selected alternatives: 3-stage Bardenpho (A2O), 5-stage Bardenpho (5BP), sequencing batch reactor (SBR), and membrane bioreactor (MBR). Combining the results of calibrated FAHP and GRA provided the overall ranking of alternatives. Results showed that each sector prioritized different factors in the selection of the optimal BNR technology. The academe considers socio-environmental (0.43) as the most preferred criterion, while the regulatory agency and industry consider financial (0.36) and implementability (0.57), respectively. Overall, the three sectors agreed that the sequential batch reactor (SBR) is the optimal BNR technology (GRG = 0.69 - 0.79).

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.