border fence in ocean between imperial beach and tijuana

Big Ideas Project Proposals

Big Ideas seeks to combine, leverage and promote San Diego State’s distinctive strengths for the betterment of the world. Faculty from Blue Gold were part of the Big Ideas for Reimagining Transboundary Water. Read the SDSU NewsCenter story on Big Ideas for Transborder Solutions.

Problem statement. Disadvantaged coastal communities near the US-Mexico border, e.g. the City of Imperial Beach, are one of the most vulnerable communities to climate change and sea-level rise in California and are already experiencing destructive flooding consequences, according to their City managers.

Project objective. This project explores novel engineered solutions to advance the sustainability and resilience of disadvantaged coastal communities, particularly of those located near the US-Mexico border, against the compound impacts of climate change through decentralization. Compound events in this context refers to exacerbated inundation conditions when multiple flooding pathways coincide, e.g. intensified precipitation, sea-level rise (SLR) and SLR-driven groundwater rise. The central hypothesis of this project is that sustainable and resilient infrastructure to manage water supply and flooding in coastal areas requires a paradigm shift toward informed decisions respectively aimed at (i) enhancing sustainability by balancing the local water budget through decentralization and (ii) enhancing resilience against compound flooding in which multiple flooding sources coincide. Projections of SLR increasingly needs to consider the extent and magnitude of flooding associated with the interconnections between SLR and shallow coastal aquifers, as well as the expected compound flooding under typical precipitation events (as opposed to infrequent extreme events). Therefore, this project aims to (i) establish a mechanistic framework to analyze important stressors to water infrastructure of disadvantaged communities and (ii) develop a novel decentralized water infrastructure to enhance their sustainability and resilience. 

Use of funding. This project has received internal seed funding for the proof of concept, e.g. Emergency Spring Funding for Research, Scholarship and Creative Activities (RSCA). The PI is now actively looking for external support to conduct full-scale research for analyzing the risks of compound flooding and to design engineered solutions to enhance the resilience against flooding. For instance, the above-mentioned disadvantaged areas do not have any groundwater table measurements available, while their residents are suffering from the rising groundwater issues due to SLR. Therefore, the funding for this project will be used to develop groundwater table sensing in these areas, and the observations will be used for risk assessment and resilience planning.

Research team. Hassan T. Davani (PI), Yousef Sangsefidi (PhD Student).

Customer, potential. State Agencies, e.g. San Diego Regional Water Quality Control Board and CA State Water Quality Control Board. Local municipalities, e.g. The City of San Diego, The City of Imperial Beach and The County of San Diego. For instance, the City of Imperial Beach has officially indicated that (i) they are interested in this project, (ii) willing to participate in the designated outreach activities, and most importantly (iii) eager to apply the project findings into action in order to enhance their sustainability and resilience.

Problem statement. Microplastics are emerging pollutants found in coastal waters, predominantly arising from stormwater discharges. Tijuana river suffers from lack of stormwater management measures, and thus is known as a major source of a variety of stormwater pollutants in the US-Mexico transborder region. Microplastics are dangerous pollutants, and have been recently found in human bodies including the placentas of unborn babies [Guardian, Dec 2020]. The current global microplastic particles have been estimated to total 15−51 trillion particles [van Sebille E., et al. 2015]. Although some microplastics are designed and manufactured for use in industry and personal care products (which are mostly banned to date), recent studies show that the majority of microplastics originate from the breakdown of larger plastic debris as a result of UV radiation and abrasion, and thus their generation is out of control.

Project objective. After MPs are discharged into the ocean, they are widely circulated and dispersed by the flow currents, where they pose risks to large populations of marine organisms through ingestion. Therefore, before MPs massively enter the ocean through stormwater runoff, it is critical to design engineered sequestration measures, e.g. advanced Green Infrastructure systems. This project aims to advance the capability of Green Infrastructure to sequester microplastics. Specifically, this project optimizes the design and filtration mechanisms of Green Infrastructure for removing microplastics from the stormwater before it discharges to the coastal waters. 

Use of funding. This project has received internal seed funding for the proof of concept, e.g. Assigned Time for Research, Scholarship and Creative Activities (RSCA), University Grant Program (UGP) and CSU Council on Ocean Affairs, Science & Technology (COAST). The PI is now actively looking for external support to conduct full-scale research for maximizing the microplastic sequestration processes. Funding will be used to (i) develop bench-scale Green Infrastructure systems by testing a variety of different filtration mechanisms to maximize the sequestration capability and next (ii) test the optimum bench-scale system in real stormwater systems supported by field measurements and monitoring. 

Research team. Hassan T. Davani (PI), Ryan McDowell (MS Student)

Customer, potential. Local municipalities, e.g. The City of San Diego, The City of Imperial Beach and The County of San Diego.

Problem statement. Every day, under-served communities on both sides of the US-Mexico border lack access to clean water and sanitation. Our team recognizes that extreme surface water pollution in Tijuana and many rapidly urbanizing areas is, in large part, due to the compounding problems of lack of wastewater treatment and inability to control soil erosion. Alternatives are needed to supplement existing wastewater infrastructure and provide clean water for greening and revitalizing urban areas in water scarce regions.

Project objective.  Our overarching goal is to innovate low-maintenance, decentralized-scale, water reuse technologies driven by community needs that also address water scarcity and the critical lack of urban green spaces. This project will be a collaboration between SDSU and El Colegio de la Frontera Norte, with research performed at the Ecoparque Decentralized Wastewater Treatment Plant in Tijuana, Mexico. Our interdisciplinary team will pursue five interrelated objectives: 1) recover nutrients and energy from wastewater, 2) remove pathogens and emerging chemicals to make water suitable for onsite water reuse and urban greening, 3) monitor performance using smartphone-based sensors, 4) apply life cycle inventory to evaluate the sustainability of decentralized wastewater treatment systems, and 5) support equitable urban greening and meet sanitation needs of communities. 

Use of funding. Funding for this project would support:

  1. Installation of novel wastewater treatment technologies that produce clean water and recover nutrients and energy 
  2. Community focus group sessions to inform and guide the project
  3. Novel sensor monitoring and advanced chemical assessment
  4. Assessment of life cycle impacts and sustainability of decentralized technologies
  5. Onsite technical support at the facility in Tijuana and training of US and Mexican students

Research team. Natalie Mladenov, Christy Dykstra, Gabriela Muñoz Melendez, Hassan Tavakol-Davani, Sean Park, Eunha Hoh, Carolina Prado

Problem statement. Impaired water quality threatens human health and ecosystems, but pollution, including from sewer system breaks and rain storms, can be difficult to predict, and there are few real-time water quality monitoring stations in the San Diego-Tijuana Border region.  

Project objective.  We are developing systems to monitor water quality in real-time, including proxies for bacteria concentrations, using telemetry and advanced water quality monitoring systems. Two existing stations have been installed and are functioning on the San Diego River at Mission Trails, and in the Tijuana Estuary, funded by the J.W Sefton Foundation and US EPA.

Use of funding.  Funding for this project would support:

  1.  Development of a mobile app to share real-time data on smartphones

  2. Storm water sampling to identify the sources of contamination in the San Diego and Tijuana Rivers.

  3. Continued operation and maintenance of existing stations

  4. Workshops to demonstrate project capabilities to industry and government stakeholders

  5. Cross-border collaboration to help identify pollution sources and causes in Tijuana.

Research team. Trent Biggs, Natalie Mladenov


Problem statement. Water conservation projects in the Imperial Valley have contributed to declining groundwater tables across the border in the Mexicali Valley, and more recent policy includes direct water transfers from Mexicali to US Cities, but the impacts of these declines and transfers on the agricultural community, including agribusiness and smallholder farmers in Mexico, has not been determined. Not only is understanding the impacts of changing water supply for smallholder farmers important to inform future policy as US Cities continue to grow, but so is understanding how farmers are adapting and adjusting their agricultural practices to these changes.

Project objective. Combine remote sensing and interviews and focus groups with farmers to determine the drivers and impacts of changing water resources, with a focus on the impact of the lining of the All American Canal and direct water transfers from Mexicali to US cities. Results will inform future water policies.

Use of funding. Funding would support:

  1. Travel for SDSU MS and BS students to visit Mexicali for interviews with farmers.

  2. Research expenses to conduct interviews and focus groups.

  3. Stipends to train US and Mexican students in the use of remote sensing to identify hotspots of agricultural change.

  4. Workshops with colleagues at Universities in Mexico to support transboundary cooperation on remote sensing, groundwater assessment, and interviews.

  5. Community events to share the results of the research and obtain community perspectives and feedback.

Research team. Trent Biggs, Amy Quandt, Alfonso Cortez Lara (COLEF), Jorge Ramirez-Hernandez (UABC).

Problem statement. The Tijuana River is a heavily impacted water body that has received a lot of community and political attention over the past decades. Though the beach and estuarine areas are monitored for regulatory compliance, these assessments do not reflect the vast number of pollutants in this watershed. While the pollution itself is of environmental interest, the risk for human exposures and hazards posed are very poorly understood.

Project objective. Characterize and quantify the chemical and microbiological species found throughout the Tijuana River watershed, and contextualize these in community exposures relevant to public health.

Use of funding. We have recently conducted a pilot study assessing the pollution at several timepoints in surface waters, specifically using:

  • Metagenomics (complete list of bacteria, viruses, and eukaryota in water)

  • Non-targeted chemical analysis (comprehensive list of chemicals in water)

However, these data are environmental concentrations but do not provide information about exposures to the local communities which may be disproportionately impacted by this pollution. Our goal is to provide a baseline of pollution metrics, but to conduct an exposure assessment in nearby residential and commercial zones. 

Research team. Kari Sant (SPH), Eunha Hoh (SPH), Scott Kelley (Biology)

Problem statement. Environmental monitoring for emerging pollutants such as pathogens and emerging chemical contaminants is cost-prohibitive for many water authorities, environmental regulatory agencies, and wastewater treatment plants. The lack of information complicates the evaluation of scenarios for interventions intended to reduce pollutant loadings to the environment. For example, the US EPA is currently evaluating 10 alternative solutions to reduce environmental and human health impacts from transboundary flows in the Tijuana River watershed. However, the evaluation of scenarios like this through environmental monitoring is costly and time-consuming. The incorporation of machine learning and artificial intelligence algorithms into the meta-analysis of research from the literature on the fate and transport of pollutants to the environment can provide prior information that can assist with targeted environmental monitoring to assess such scenarios and to monitor and evaluate the effectiveness of interventions.

Project objective. The objective of this project is to develop a geospatial web application that will allow for geospatial and temporal predictions of the emissions, concentrations, and risks associated with contaminants originating from wastewater and excreta. Our team has developed beta versions of two different web applications for predicting pathogen flows and emissions to the environment: 1) the Treatment Plant Sketcher Tool; and 2) the Pathogen Flow and Mapping Tool. The “Sketcher Tool” allows users to construct a custom flow diagram that characterizes the configuration and design of a wastewater treatment facility, predict the removal efficiency of pathogens (viruses, bacteria, protozoa, helminths) through the treatment plant based on data from the literature, and estimate the fraction of pathogens emitted from the treatment plant in treated effluent vs. sludge/biosolids. The Pathogen Flow and Mapping Tool predicts and visualizes pathogen emissions with respect to the sanitation infrastructure present in any country or region, allowing users to identify pathogen hotspots, areas to improve sanitation coverage, and testing how changes in the sanitation service chain affects pathogen reduction and emissions.

Use of funding. Funding for this project will support the following activities:

  • Develop machine learning and artificial intelligence algorithms to automatically populate databases with information about the occurrence, persistence, and removal of emerging chemical and microbial contaminants in treatment systems and the environment.

  • Develop a tool that maps pathogen emissions and predicts pathogen concentrations in the entire US-Mexico transboundary water region, using data from the databases.

  • Use the Sketcher tool to compile a catalog of all sanitation and wastewater treatment systems located within three transboundary watersheds, including the Tijuana River watershed and incorporate them into the contaminant emissions maps.

  • Validate the model with targeted sampling and analysis of pathogens at a selection of three transboundary rivers, including the Tijuana River.

Research team. Matthew E. Verbyla (Environmental Engineering), Nynke Hofstra (Wageningen University), Panagis Katsivelis (Venthic Technologies)

Customer, potential. US EPA, CalEPA, CONAGUA

Minimum viable product. Long-term goal of this web application is to reduce the costs of environmental water quality and health assessments by 30%. Below is a summary of the anticipated user journey:


  • Public regulatory agencies

  • Health authorities

  • Regional planning authorities

  • Wastewater treatment authorities


  1. Collect sanitation and treatment plant data

  2. Collect/compile data on population, health, and demographics

  3. Run the model under baseline and several intervention scenarios

  4. Collect samples for water quality analysis at identified hotspots before and after the implementation of targeted intervention

  5. Utilize the tool and update/improve the algorithms through M&E data collection after the intervention

Story Ending

  • Taxpayer money (and time) saved on environmental health assessments (increases with each subsequent user)

  • Improved health outcomes, especially in underserved communities

  • Improved economic outcomes from tourism

Problem statement. Microbial source tracking is a method developed in the 1990s based on the concept that the origin of fecal pollution can be traced using microbiological, genotypic, phenotypic, and chemical methods. Applications have been widely adopted by researchers and regulatory agencies throughout the world including the US EPA, which just published its first standardized protocol on the use of HF183 Bacteroides assay to distinguish human-associated bacterial fecal pollution in ambient waters. However, to identify and resolve the contamination of surface waters from human fecal contamination, there is a need to distinguish between different sources of human fecal contamination, such as leaching from onsite septic systems, runoff from open defecation (e.g., homeless encampments), leaking from sanitary sewer collection systems, and the illegal/illicit discharges of wastewater to storm sewer systems. The hypothesis for this project is that the use of different human-associated chemical and microbial tracking methods in combination can effectively distinguish between different sources of human-associated fecal pollution. For example, HF183 is a gene target of human-associated strains of the commensal gut microorganism Bacteroides; pepper mild mottle virus (PMMoV) is a dietary-based human-associated viral fecal indicator. Both have been used for microbial source tracking, but PMMoV has much greater persistence in the environment than HF183, and as a virus, it also has greater ability to move through subsurface waters compared to Bacteroides spp. Caffeine and sucralose are both dietary-based human-associated chemical indicators of wastewater pollution, but sucralose is much more persistent than caffeine in the environment.

Project objective. The objective of this project is to develop next-generation source tracking methods based on multiplex assays of chemical tracers and microbial markers that have contrasting characteristics of environmental persistence, size, origin, and affinity to solids. Specifically, we would use metagenomic sequencing and non-targeted chemical analysis of river samples during storm events to identify changes in the relative abundance of different microbial and chemical markers, then correlate those trends with observations made from samples of groundwater, surface runoff, and interflow collected throughout the watershed. Through analysis of these results, we would identify the combination of markers that would most likely distinguish between the following sources of human fecal contamination: 1) recent contamination by sewage (e.g., sanitary sewer overflows); 2) recent contamination by sewage leaching through the subsurface (e.g., leaky sanitary sewer mains); 3) recent contamination by illegal/illicit discharges to storm sewer systems; 4) recent and older contamination by surface runoff (e.g., open defecation); 5) older contamination by the flushing of contaminants from the subsurface during interflow; and 6) contamination originating from septic leach fields.

Use of funding. Funding for this project will support the following activities:

  • Develop novel multiplex assays for chemical tracers and microbial markers

  • Validate their application in a controlled surface water environment with measurements and estimates of surface runoff, groundwater-fed flows to surface waters, and interflow during storm events

  • Test the use of the next generation source tracking methods in the Tijuana River watershed during storm events

Research team. Natalie Mladenov (Environmental Engineering), Matthew E. Verbyla (Environmental Engineering), Hilary McMillan (Geography), and Eunha Hoh (Public Health)

Customer, potential. US EPA, California Water Board

Problem statement. Water quality varies tremendously in space and time, but many constituents of concern require expensive laboratory techniques for analysis.  There is a pressing need for portable water quality monitoring systems that avoid the need for sample collection and can be integrated into real-time monitoring systems.

Project objective. The project will develop a portable water quality sensor for advanced characterization of water quality, including fluorescent organic compounds (tryptophan, organic matter), anthropogenic indicators (caffeine, sucralose) and contaminants of emerging concern (CECs: hormones, pharmaceuticals).

Use of funding. The funding will be used to support students and procure equipment for developing and testing the equipment.  This will involve both instrument development and laboratory analysis for bacteria, indicators, and CECs.

Research team. Bill Tong (instrument lead), Eunha Hoh (CEC analysis); Natalie Mladenov (bacteria), Trent Biggs (turbidity, field instrumentation).

Customer, potential. Governmental agencies (Water Control Board), consulting industry.


Problem statement. Southern California’s coastal water quality deteriorates after storm events, creating a hazard to recreational users and ecosystems. Debris and pollutants wash into urban rivers to create plumes stretching several kilometers offshore. To address marine debris, the California Trash Amendment mandate requires that within 10 years of permitting, particles >5 mm are excluded from storm drains using inlet filters. However, debris that originates in the river margins from a large homeless community is not addressed by this mandate. Therefore, this project will determine the relative loading of debris of different materials and sizes from storm drain outfall and river margin sources.

Project objective. This report will make the first estimate of the characteristics and contribution of trash from homeless encampments within river margins to the debris exported to the ocean. Encampments are a significant risk for marine debris generation: large quantities of river margin trash from encampments are well documented, and are increasing rapidly under current policing regimes - surveys reported a 500% increase in San Diego River encampments between March and June of 2020. We envisage that this project will carry out initial work in the San Diego River, and there is great potential to extend the techniques cross-border to the Tijuana River and its tributaries.

This project will determine:

  1. Characteristics of debris generated from homeless encampments 

  2. Degradation and fragmentation risk of encampment debris prior to outfall to the ocean

  3. Relative loading of different materials/size debris from storm drain vs encampment sources

  4. Potential management strategies for debris reductions from encampment sources.

Use of funding. Funding will support deployment and testing of new technologies such as drone surveys to detect and map river and marine debris. It will support field work to gather information and ground-truth data on debris properties, and lab work to understand how debris decays and fragments under sunlight and in-river conditions. To support community solutions, we will survey unhoused residents to determine drivers of debris-generating behaviors, and to solicit solutions for waste reduction.

Research team. Hilary McMillan, Natalie Mladenov, Trent Biggs, Alicia Kinoshita, Hassan Davani, Megan Welsh.

Problem statement. In water scarce regions, on-site sanitation (OSS) is often accomplished using dry toilets or pit latrines that are not waterborne (non-flushing) due to 1) lack of water, 2) lack of water infrastructure, or 3) necessity to prioritize what little water is available for potable and other more critical water uses. Due to lessened degradation in dry OSS, these systems fill up and need to be emptied and are often sources of pollution to soils, groundwater, and surface water.

Project objective. The objectives of this project are to treat and repurpose dilute anaerobic digestion effluent for toilet flushing. Research will test the influence of different waste introduction scenarios on digester chemical makeup, evaluate the longevity of the treatment system, and investigate treatment options that meet water reuse standards, reduce the buildup of nutrients, and remove substances that inhibit natural degradation processes.

Use of funding. Funding would support laboratory and field activities as follows:

  • Surveys of communities lacking sanitation for preferences
  • Research on innate degradation processes under different waste introduction scenarios
  • Research on secondary treatment and polishing units
  • Construction of a prototype
  • Deployment and testing of prototype

Research team. Natalie Mladenov (PI), Lily Astete Vasquez (PhD student)

Customer potential. Studies show that users have a preference for flushing toilets and are willing to pay more for waterborne sanitation; however, where access to water is limited, people cannot justify fetching water from distant sources for the purpose of toilet flushing. A toilet that flushes with treated wastewater, where contact with the water is minimized, can be practical, low cost, easy-to-maintain, and attractive to users. This design has potential applications in informal settlements in developing communities, mobile sanitation units to provide toilets to citizens experiencing homelessness, national parks, refugee camps, and disaster-relief scenarios.

“Minimum value proposition.” This waterless, flushing toilet will provide a low-cost, effective, and attractive sanitation solution for those who lack access to water and sanitation.

Reimagining Transboundary Water