DMsan: A Multi-Criteria Decision Analysis Framework and Package to Characterize Contextualized Sustainability of Sanitation and Resource Recovery Technologies.

In resource-limited settings, conventional sanitation systems often fail to meet their goals-with system failures stemming from a mismatch among community needs, constraints, and deployed technologies. Although decision-making tools exist to help assess the appropriateness of conventional sanitation systems in a specific context, there is a lack of a holistic decision-making framework to guide sanitation research, development, and deployment (RD&D) of technologies. In this study, we introduce DMsan-an open-source multi-criteria decision analysis Python package that enables users to transparently compare sanitation and resource recovery alternatives and characterize the opportunity space for early-stage technologies. Informed by the methodological choices frequently used in literature, the core structure of DMsan includes five criteria (technical, resource recovery, economic, environmental, and social), 28 indicators, criteria weight scenarios, and indicator weight scenarios tailored to 250 countries/territories, all of which can be adapted by end-users. DMsan integrates with the open-source Python package QSDsan (quantitative sustainable design for sanitation and resource recovery systems) for system design and simulation to calculate quantitative economic (via techno-economic analysis), environmental (via life cycle assessment), and resource recovery indicators under uncertainty. Here, we illustrate the core capabilities of DMsan using an existing, conventional sanitation system and two proposed alternative systems for Bwaise, an informal settlement in Kampala, Uganda. The two example use cases are (i) use by implementation decision makers to enhance decision-making transparency and understand the robustness of sanitation choices given uncertain and/or varying stakeholder input and technology ability and (ii) use by technology developers seeking to identify and expand the opportunity space for their technologies. Through these examples, we demonstrate the utility of DMsan to evaluate sanitation and resource recovery systems tailored to individual contexts and increase transparency in technology evaluations, RD&D prioritization, and context-specific decision making.

Control of Pre-formed Halogenated Disinfection Byproducts with Reuse Biofiltration.

Disinfection byproduct (DBP) pre-formation is a major issue when prechlorination is used before or during advanced treatment of impacted drinking water sources. Control strategies for pre-formed DBPs before final disinfection, especially for currently nonregulated although highly toxic DBP species, are not yet established. This study evaluated the biodegradation potential of pre-formed DBPs, including haloacetonitriles (HANs), haloacetamides (HAMs), and haloacetaldehydes (HALs), during biofiltration with sand, anthracite, and biological activated carbon of three wastewater effluents under potable reuse conditions. Up to 90%+ removal of di- and trihalogenated HANs, HAMs, and HALs was observed, and removal was associated with active heterotrophic biomass and removal of biodegradable organic carbon. Unlike the microbial dehalogenation pathway of haloacetic acids (HAAs), removal of HANs and HAMs appeared to result from a biologically mediated hydrolysis pathway (i.e., HANs to HAMs and HAAs) that may be prone to inhibition. After prechlorination, biofiltration effectively controlled pre-formed DBP concentrations (e.g., from 271 µg/L to as low as 22 µg/L in total) and DBP-associated calculated toxicity (e.g., 96%+ reduction). Abiotic residual adsorption capacity in biological activated carbon media was important for controlling trihalomethanes. Overall, the toxicity-driving DBP species exhibited high biodegradation potential and biofiltration showed significant promise as a pre-formed DBP control technology.

Impacts of carbon-based advanced treatment processes on disinfection byproduct formation and speciation for potable reuse.

For the potable reuse of municipal wastewater effluent, carbon based advanced treatment (CBAT) using coagulation, ozonation, biofiltration and/or granular activated carbon (GAC) adsorption is a promising approach for controlling disinfection byproduct (DBP) formation. However, CBAT can also favor a shift in DBP formation to more toxic brominated DBP species. To protect public health, treatment-specific DBP formation and speciation trends need to be identified and understood. First, this study systematically evaluated the treatment of six wastewater effluents with four CBAT process trains (experimental n was 55) and measured DBP formation and speciation trends. Overall, CBAT decreased DBP formation by >90% and GAC preferentially removed highly-reactive effluent organic matter as indicated by lower yields of both highly-forming and highly-toxic classes of carbonaceous and nitrogenous DBPs. Since GAC treatment also induced systematic speciation changes by increasing the ratio of bromide to dissolved organic matter, the second part of this study focused on understanding the health impacts of DBP speciation changes on calculated additive toxicity (CAT). Based on the evaluation of 20 DBPs, measured using established methods, the CAT values from cyto- and genotoxicity metrics decreased by as much as 85% due to high levels of precursor removal by GAC. Expanding the evaluation to include 52 DBPs, measured using more extensive analytical methods, resulted in the same conclusions. This study also developed a "speciation potency" metric, that re-scales class-by-class speciation trends using toxic potency factors (e.g., cytotoxicity [LC50]). The observed shifts in DBP speciation after treatment increased the class-level toxic potency factors by up to a factor of 4; a greater amount of precursor removal is required for treatment to reduce toxicity, which was achieved with CBAT trains. This proposed approach of combining speciation potency with DBP yields enables evaluation of DBP-associated risk with easily measured surrogates (i.e., bromide and dissolved organic carbon [DOC]). By identifying and quantitatively comparing DBP formation and speciation trends over multiple wastewater effluents and treatment trains, this study demonstrates that CBAT can be a robust approach to DBP precursor removal for potable reuse.

Re-Envisioning Sanitation As a Human-Derived Resource System.

Sanitation remains a global challenge, both in terms of access to toilet facilities and resource intensity (e.g., energy consumption) of waste treatment. Overcoming barriers to universal sanitation coverage and sustainable resource management requires approaches that manage bodily excreta within coupled human and natural systems. In recent years, numerous analytical methods have been developed to understand cross-disciplinary constraints, opportunities, and trade-offs around sanitation and resource recovery. However, without a shared language or conceptual framework, efforts from individual disciplines or geographic contexts may remain isolated, preventing the accumulation of generalized knowledge. Here, we develop a version of the social-ecological systems framework modified for the specific characteristics of bodily excreta. This framework offers a shared vision for sanitation as a human-derived resource system, where people are part of the resource cycle. Through sanitation technologies and management strategies, resources including water, organics, and nutrients accumulate, transform, and impact human experiences and natural environments. Within the framework, we establish a multitiered lexicon of variables, characterized by breadth and depth, to support harmonized understanding and development of models and analytical approaches. This framework's refinement and use will guide interdisciplinary study around sanitation to identify guiding principles for sanitation that advance sustainable development at the nature-society interface.

Sorption, coagulation, and biodegradation for graywater treatment.

Population growth and climate change are exacerbating water scarcity. Graywater recycling could reduce water demand but it is not commonly practiced because of high treatment costs. Biochar, an emerging low-cost alternative sorbent with potential environmental benefits for graywater treatment, was compared to activated carbon (AC) for removing dissolved organic carbon (DOC) from graywater. The impact of pretreatments (coagulation, biodegradation) were also evaluated. Among five biochars tested, a wood-based biochar was the most effective for graywater treatment, but AC removed more DOC. Sorption resulted in a greater percent removal of ultraviolet (UV) absorbance than DOC or free chlorine demand. Graywater regulations could not be met by sorption alone but could be met with pretreatment before sorption. After biodegradation, irrigation and toilet flushing treatment targets could be achieved with AC doses less than 0.7 g/L, while a biochar dose of about 1 g/L was needed to achieve the irrigation treatment targets. For DOC removal, alum coagulation at a dose of 30 mg/L was a less effective pretreatment than biodegradation. Pretreatment and sorption to decrease turbidity and increase UV transmittance could be effective for the potential use of UV disinfection, thus creating an effective graywater non-potable reuse approach.

Analyzing Sanitation Sustainability Assessment Frameworks for Resource-Limited Communities.

Diverse and numerous sanitation sustainability assessment frameworks have been created to enhance the ability of systems to provide safe sanitation services, especially in resource-limited contexts. However, many go unused while new frameworks are developed and high sanitation system failure rates persist. To better support the sustainable development goal around global sanitation, there is a need to better understand how sanitation sustainability is defined and measured and the potential advantages and disadvantages of existing assessment frameworks. A subset of existing sanitation sustainability assessment frameworks was reviewed after applying each to evaluate multiple successful and failed community sanitation systems in India. Overall, the evaluated frameworks did not share a sanitation sustainability definition or core set of essential indicators. Many indicators lacked clear definitions and guidance on data collection and analysis. When evaluating framework effectiveness, differentiations between successful and failed cases varied greatly between frameworks. Potential improvements include indicator pilot testing to verify measurement feasibility and that they provide expected results; context-specific weightings; and project-specific framework selection. Clarifying and improving sanitation sustainability assessment frameworks could increase their effectiveness and use, leading to better decision-making and improved public and environmental health, economic viability, and sanitation use and acceptance.

A new framework for small drinking water plant sustainability support and decision-making.

Public drinking water system decisions about treatment processes are becoming more challenging, especially as regulations become more stringent and source water quality degrades. For small systems that serve <10,000 people, treatment decisions are particularly difficult due to limited resources and because they do not currently have resources to help them make informed and sustainable decisions using environmental, social, and economic criteria. Therefore, a user-friendly sustainability assessment framework, which compares treatment processes relevant to a wide variety of small drinking water systems, was constructed. In summary, the framework uses life cycle assessment and multiple-criteria decision analysis to comprehensively evaluate twelve decision criteria, developed specific to small drinking water systems; the framework then uses an aggregation approach to identify and navigate multiple trade-offs and make a final recommendation based on stakeholder values. Four hypothetical scenarios were examined to show the framework's applicability to diverse small systems, ability to help stakeholders navigate trade-offs, and engineering relevance. The framework is universal in its capacity to evaluate systems with different design parameters, source waters, treatment criteria, and stakeholder preferences.

Engineered Ureolytic Microorganisms Can Tailor the Morphology and Nanomechanical Properties of Microbial-Precipitated Calcium Carbonate.

We demonstrate for the first time that the morphology and nanomechanical properties of calcium carbonate (CaCO3) can be tailored by modulating the precipitation kinetics of ureolytic microorganisms through genetic engineering. Many engineering applications employ microorganisms to produce CaCO3. However, control over bacterial calcite morphology and material properties has not been demonstrated. We hypothesized that microorganisms genetically engineered for low urease activity would achieve larger calcite crystals with higher moduli. We compared precipitation kinetics, morphology, and nanomechanical properties for biogenic CaCO3 produced by two Escherichia coli (E. coli) strains that were engineered to display either high or low urease activity and the native producer Sporosarcina pasteurii. While all three microorganisms produced calcite, lower urease activity was associated with both slower initial calcium depletion rate and increased average calcite crystal size. Both calcite crystal size and nanoindentation moduli were also significantly higher for the low-urease activity E. coli compared with the high-urease activity E. coli. The relative resistance to inelastic deformation, measured via the ratio of nanoindentation hardness to modulus, was similar across microorganisms. These findings may enable design of novel advanced engineering materials where modulus is tailored to the application while resistance to irreversible deformation is not compromised.

The use of qualitative comparative analysis to identify pathways to successful and failed sanitation systems.

Sanitation systems globally fail at high rates. Researchers and practitioners attribute the causes of both sanitation success and failure to numerous factors that include technical and non-technical issues. A comprehensive understanding of what leads to sanitation failure and how to achieve sanitation success is imperative to prioritize the use of limited resources. To determine which combinations of causal conditions led to successful and failed sanitation systems, we applied fuzzy-set qualitative comparative analysis to 20 cases in Karnataka and Tamil Nadu, India with small-scale sanitation systems. Two pathways led to successful sanitation systems, and four pathways led to failed sanitation systems. All successful systems required Sufficient O&M Funds, a Clear O&M Plan, and Technical Support in addition to either Addressed Sanitation Priorities and Community Participation in Planning or Behavior Change Education and Municipality Involved in Planning. All failed systems had Lack of Municipality in Planning, Unaddressed Sanitation Priorities, and No Technical Support. Most failed systems also had No Clear O&M Plan, Poor Construction Quality, Lack of Community Participation in Planning, and Insufficient O&M Funds. Two failed cases had unique pathways because Government Barriers permanently disrupted use and maintenance. Overall, implementing organizations who initiate sanitation projects in resource-limited communities should ensure that (1) communities have adequate technical and financial resources for maintenance; (2) community and municipality stakeholders are engaged in planning and know their maintenance responsibilities; and (3) appropriate technologies are selected that meet community needs and achieve community buy-in.

Priority Addressment Protocol: Understanding the Ability and Potential of Sanitation Systems to Address Priorities.

Sanitation acceptance is unlikely if user priorities are not addressed. However, sanitation systems are commonly implemented, especially in resource-limited communities, without incorporating local context. Understanding sanitation systems' abilities to address different priorities will further inform technology selection processes. Therefore, a protocol was created to identify priorities and measure how well sanitation systems address them, based upon their importance to a community. This protocol was applied to 20 community-based sanitation systems in India. Overall, 52 sanitation and 40 community priorities were identified; most, along with their relative importance, were case-specific and not yet identified in literature. Existing sanitation systems poorly addressed priorities. Nonfunctional systems addressed the fewest, but, if use and maintenance were improved, they had the potential to address priorities almost as well as functional systems. Resource recovery systems addressed the most priorities, but there was usually minimal benefit to adding all three resources to an existing system; biogas and water had greater potential to address more priorities than compost. This priority addressment protocol can help identify the most appropriate technologies and strategies to improve technology development and success.

Rational Control of Calcium Carbonate Precipitation by Engineered Escherichia coli.

Ureolytic bacteria ( e.g., Sporosarcina pasteurii) can produce calcium carbonate (CaCO3). Tailoring the size and shape of biogenic CaCO3 may increase the range of useful applications for these crystals. However, wild type Sporosarcina pasteurii is difficult to genetically engineer, limiting control of the organism and its crystal precipitates. Therefore, we designed, constructed, and compared different urease operons and expression levels for CaCO3 production in engineered Escherichia coli strains. We quantified urease expression and calcium uptake and characterized CaCO3 crystal phase and morphology for 13 engineered strains. There was a weak relationship between urease expression and crystal size, suggesting that genes surrounding the urease gene cluster affect crystal size. However, when evaluating strains with a wider range of urease expression levels, there was a negative relationship between urease activity and polycrystal size (e.g., larger crystals with lower activity). The resulting range of crystal morphologies created by the rationally designed strains demonstrates the potential for controlling biogenic CaCO3 precipitation.

A Unified Modeling Framework to Advance Biofuel Production from Microalgae.

Modeling efforts to understand the financial implications of microalgal biofuels often assume a static basis for microalgae biomass composition and cost, which has constrained cultivation and downstream conversion process design and limited in-depth understanding of their interdependencies. For this work, a dynamic biological cultivation model was integrated with thermo-chemical/biological unit process models for downstream biorefineries to increase modeling fidelity, to provide mechanistic links among unit operations, and to quantify minimum product selling prices of biofuels via techno-economic analysis. Variability in design, cultivation, and conversion parameters were characterized through Monte Carlo simulation, and sensitivity analyses were conducted to identify key cost and fuel yield drivers. Cultivating biomass to achieve the minimum biomass selling price or to achieve maximum lipid content were shown to lead to suboptimal fuel production costs. Depending on biomass composition, both hydrothermal liquefaction and a biochemical fractionation process (combined algal processing) were shown to have advantageous minimum product selling prices, which supports continued investment in multiple conversion pathways. Ultimately, this work demonstrates a clear need to leverage integrated modeling platforms to advance microalgae biofuel systems as a whole, and specific recommendations are made for the prioritization of research and development pathways to achieve economical biofuel production from microalgae.

Life Cycle Environmental Impacts of Disinfection Technologies Used in Small Drinking Water Systems.

Small drinking water systems serve a fifth of the U.S. population and rely heavily on disinfection. While chlorine disinfection is common, there is interest in minimizing chemical addition, especially due to carcinogenic disinfection byproducts and chlorine-resistant pathogens, by using ultraviolet technologies; however, the relative, broader environmental impacts of these technologies are not well established, especially in the context of small (<10 000 people) water systems. The objective of this study was to identify environmental trade-offs between chlorine and ultraviolet disinfection via comparative life cycle assessment. The functional unit was the production of 1 m3 of drinking water to U.S. STANDARDS: Treatment included cartridge filtration followed by either chlorine disinfection or ultraviolet disinfection with chlorine residual addition. Environmental performance was evaluated for various chlorine contact zone materials (plastic, concrete, steel), ultraviolet validation factors (1.2 to 4.4), and electricity sources (renewable; U.S. average, high, and low impact grids). Performance was also evaluated when filtration and chlorine residual were not required. From a life cycle assessment perspective, replacing chlorine with UV was preferred only in a limited number of cases (i.e., high pumping pressure but filtration is not required). In all others, chlorine was environmentally preferred, although some contact zone materials and energy sources had an impact on the comparison. Utilities can use these data to inform their disinfection technology selection and operation to minimize environmental and human health impacts.

A stability assessment tool for anaerobic codigestion.

Anaerobic codigestion allows for greater resource recovery from organic substrates and provides opportunities for more stable operation than mono-digestion. Despite these benefits, the adoption of codigestion is limited because it can introduce operational complexity and suffers from some of the same challenges as mono-digestion, such as ammonia inhibition and nutrient imbalances. There is a need for rapid and cost-effective assessments that can provide insight to design engineers as they explore the valorization of local organic waste streams and seek to maintain or improve digester stability. To address this need, we developed and tested a tool that can yield useful stability indicators, performance predictions, and substrate selection protocols for codigestion. This tool uses quantitative, empirical data on stability indicators within an assessment framework to evaluate a digester's process stability. The tool's accuracy was tested using real and simulated digester data, and the importance of the nitrogen and lipid composition of a substrate was identified. The resulting stability assessment tool improves our fundamental understanding of codigestion, provides a mechanism to reduce the number of experiments, and guides selection of appropriate substrate combinations that can maximize energy recovery during codigestion without compromising process stability.

Environmental Comparison of Biochar and Activated Carbon for Tertiary Wastewater Treatment.

Micropollutants in wastewater present environmental and human health challenges. Powdered activated carbon (PAC) can effectively remove organic micropollutants, but PAC production is energy intensive and expensive. Biochar adsorbents can cost less and sequester carbon; however, net benefits depend on biochar production conditions and treatment capabilities. Here, life cycle assessment was used to compare 10 environmental impacts from the production and use of wood biochar, biosolids biochar, and coal-derived PAC to remove sulfamethoxazole from wastewater. Moderate capacity wood biochar had environmental benefits in four categories (smog, global warming, respiratory effects, noncarcinogenics) linked to energy recovery and carbon sequestration, and environmental impacts worse than PAC in two categories (eutrophication, carcinogenics). Low capacity wood biochar had even larger benefits for global warming, respiratory effects, and noncarcinogenics, but exhibited worse impacts than PAC in five categories due to larger biochar dose requirements to reach the treatment objective. Biosolids biochar had the worst relative environmental performance due to energy use for biosolids drying and the need for supplemental adsorbent. Overall, moderate capacity wood biochar is an environmentally superior alternative to coal-based PAC for micropollutant removal from wastewater, and its use can offset a wastewater facility's carbon footprint.

Life cycle comparison of environmental emissions from three disposal options for unused pharmaceuticals.

We use life cycle assessment methodology to compare three disposal options for unused pharmaceuticals: (i) incineration after take-back to a pharmacy, (ii) wastewater treatment after toilet disposal, and (iii) landfilling or incineration after trash disposal. For each option, emissions of active pharmaceutical ingredients to the environment (API emissions) are estimated along with nine other types of emissions to air and water (non-API emissions). Under a scenario with 50% take-back to a pharmacy and 50% trash disposal, current API emissions are expected to be reduced by 93%. This is within 6% of a 100% trash disposal scenario, which achieves an 88% reduction. The 50% take-back scenario achieves a modest reduction in API emissions over a 100% trash scenario while increasing most non-API emissions by over 300%. If the 50% of unused pharmaceuticals not taken-back are toileted instead of trashed, all emissions increase relative to 100% trash disposal. Evidence suggests that 50% participation in take-back programs could be an upper bound. As a result, we recommend trash disposal for unused pharmaceuticals. A 100% trash disposal program would have similar API emissions to a take-back program with 50% participation, while also having significantly lower non-API emissions, lower financial costs, higher convenience, and higher compliance rates.