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Separate collection of urine, which is only 1% of wastewater volume but contains the majority of nitrogen humans excrete, can potentially reduce the costs and energy input of wastewater treatment and facilitate recovery of nitrogen for beneficial use. Ion exchange was investigated for recovery of nitrogen as ammonium from urine for use as a fertilizer or disinfectant. Cation adsorption curves for four adsorbents (clinoptilolite, biochar, Dowex 50, and Dowex Mac 3) were compared in pure salt solutions, synthetic urine, and real stored urine. Competition from sodium and potassium present in synthetic and real urine did not significantly decrease ammonium adsorption for any of the adsorbents. Dowex 50 and Dowex Mac 3 showed nearly 100% regeneration efficiencies. Estimated ion exchange reactor volumes to capture the nitrogen for 1 week from a four-person household were lowest for Dowex Mac 3 (5 L) and highest for biochar (19 L). Although Dowex Mac 3 had the highest adsorption capacity, material costs ($/g N removed) were lower for clinoptilolite and biochar because of their substantially lower unit cost. [ABSTRACT FROM AUTHOR]

In long-term experiments with membrane aerated biofilm reactors we observed complete nitrite oxidation in highly concentrated ammonium nitrite solutions with a contaminant pH decrease to values below 3. The maximum initial concentration for ammonium was 42 mM and for nitrite was 41 mM. We hypothesized that (1) acid-tolerant ammonium oxidizing bacteria were responsible for the pH decrease, and (2) chemical processes caused complete nitrite oxidation at low pH values. To test this hypothesis we set up a mechanistic computer model based on kinetic data from literature and we validated the model with additional experiments. The simulations fitted the measurements very well. Additionally, an experiment with the inhibitor allylthiourea showed that ammonium-oxidizing bacteria were active at pH values far below 5.5. Experiments in a sterile reactor confirmed the chemical nitrite oxidation to nitrate. Nitrogen balances revealed that 8 ± 4% of the initial nitrogen (ammonium, nitrite, and nitrate) were lost during the cycles. On the basis of measurements and simulations we concluded that volatilization was responsible for the significant nitrogen loss. We estimated that about half of the lost nitrogen volatilized as nitrous acid HNO2. The rest mainly volatilized as dinitrogen N2 and nitrous oxide N2O. [ABSTRACT FROM AUTHOR]

Sanitizing human and animal waste (e.g., urine, fecal sludge, or grey water) is a critical step in reducing the spread of disease and ensuring microbially safe reuse of waste materials. Viruses are particularly persistent pathogens and can be transmitted through inadequately sanitized waste. However, adequate storage or digestion of waste can strongly reduce the number of viruses due to increases in pH and uncharged aqueous ammonia (NH3), a known biocide. In this study we investigated the kinetics and mechanisms of inactivation of the single-stranded RNA virus MS2 under temperature, pH and NH3 conditions representative of waste storage. MS2 inactivation was mainly controlled by the activity of NH3 over a pH range of 7.0-9.5 and temperatures lower than 40°C. Other bases (e.g., hydroxide, carbonate) additionally contributed to the observed reduction of infective MS2. The loss in MS2 infectivity could be rationalized by a loss in genome integrity, which was attributed to genome cleavage via alkaline transesterification. The contribution of each base to genome transesterification, and hence inactivation, could be related to the base pKa by means of a Bronsted relationship. The Bronsted relationship in conjunction with the activity of bases in solution enabled an accurate prediction of MS2 inactivation rates. [ABSTRACT FROM AUTHOR]

Ammonia oxidation decreases the pH in wastewaters where alkalinity is limited relative to total ammonia. The activity of ammonia oxidizing bacteria (AOB), however, typically decreases with pH and often ceases completely in slightly acidic wastewaters. Nevertheless, nitrification at low pH has been reported in reactors treating human urine, but it has been unclear which organisms are involved. In this study, we followed the population dynamics of ammonia oxidizing organisms and reactor performance in synthetic fully hydrolyzed urine as the pH decreased over time in response to a decrease in the loading rate. Populations of the β-proteobacterial Nitrosomonas europaea lineage were abundant at the initial pH close to 6, but the growth of a possibly novel Nitrosococcus-related AOB genus decreased the pH to the new level of 2.2, challenging the perception that nitrification is inhibited entirely at low pH values, or governed exclusively by β-proteobacterial AOB or archaea. With the pH shift, nitrite oxidizing bacteria were not further detected, but nitrous acid (HNO2) was still removed through chemical decomposition to nitric oxide (NO) and nitrate. The growth of acid-tolerant ?-proteobacterial AOB should be prevented, by keeping the pH above 5.4, which is a typical pH limit for the N. europaea lineage. Otherwise, the microbial community responsible for high-rate nitrification can be lost, and strong emissions of hazardous volatile nitrogen compounds such as NO are likely. [ABSTRACT FROM AUTHOR]

Human urine can be processed into market-attractive fertilizers like struvite; however, concerns regarding the microbial safety of such products remain. The present study evaluated the inactivation of in situ heterotrophs, total bacteria as observed by flow cytometry, and inoculated Enterococcus spp. and Salmonella typhimurium during the drying of struvite under controlled temperature (from 5 to 35 °C) and relative humidity (approximately 40 and 80%) as well as dynamic field conditions. Bacteria accumulated in the struvite cake during struvite filtration. Despite the use of sublethal temperatures, all bacteria types were subsequently inactivated to some degree during struvite drying, and the inactivation typically increased with increasing drying temperature for a given relative humidity. Heterotrophic bacteria inactivation mirrored the trend in total bacteria during struvite drying. A linear relationship was observed between inactivation and sample moisture content. However, bacteria survivor curves were typically nonlinear when struvite was dried at low relative humidity, indicating bacterial persistence. Weibull model survivor curve fits indicated that a shift in the mechanism of inactivation may occur with changing humidity. For increased efficiency of bacterial inactivation during the production of struvite, initial heating under moist conditions is recommended followed by desiccation. [ABSTRACT FROM AUTHOR]

Chlorination byproducts (CBPs) are harmful to human health and the environment. Their formation in chlorine mediated electro-oxidation is a concern for electrochemical urine treatment. We investigated the formation of chlorate, perchlorate, and organic chlorination byproducts (OCBPs) during galvanostatic (10, 15, 20 mA·cm-2) electro-oxidation of urine on boron-doped diamond (BDD) and thermally decomposed iridium oxide film (TDIROF) anodes. In the beginning of the batch experiments, the production of perchlorate was prevented by competing active chlorine and chlorate formation as well as by direct oxidation of organic substances. Perchlorate was only formed at higher specific charges (>17 Ah·L-1 on BDD and >29 Ah·L-1 on TDIROF) resulting in chlorate and perchlorate being the dominant CBPs (>90% of initial chloride). BDD produced mainly short chained OCBPs (dichloromethane, trichloromethane, and tetrachloromethane), whereas longer chained OCBPs (1,2-dichloropropane and 1,2-dichloroethane) were more frequently found on TDIROF. The OCBPs were primarily eliminated by electrochemical stripping: On BDD, this pathway accounted for 40% (dichloromethane) to 100% (tetrachloromethane) and on TDIROF for 90% (1,2-dichloroethane) to 100% (trichloromethane) of what was produced. A post-treatment of the liquid as well as the gas phase should be foreseen if CBP formation cannot be prevented by eliminating chloride or organic substances in a pretreatment. [ABSTRACT FROM AUTHOR]

This paper offers a methodology for structuring the design space for innovative process engineering technology development. The methodology is exemplified in the evaluation of a wide variety of treatment technologies for source-separated domestic wastewater within the scope of the Reinvent the Toilet Challenge. It offers a methodology for narrowing down the decision-making field based on a strict interpretation of treatment objectives for undiluted urine and dry feces and macroenvironmental factors (STEEPLED analysis) which influence decision criteria. Such an evaluation identifies promising paths for technology development such as focusing on space-saving processes or the need for more innovation in low-cost, energy-efficient urine treatment methods. Critical macroenvironmental factors, such as housing density, transportation infrastructure, and climate conditions were found to affect technology decisions regarding reactor volume, weight of outputs, energy consumption, atmospheric emissions, investment cost, and net revenue. The analysis also identified a number of qualitative factors that should be carefully weighed when pursuing technology development; such as availability of O&M resources, health and safety goals, and other ethical issues. Use of this methodology allows for coevolution of innovative technology within context constraints; however, for full-scale technology choices in the field, only very mature technologies can be evaluated. [ABSTRACT FROM AUTHOR]

The article reports on the integrated approach to sanitation, water, and hygiene to low income countries. Topics discussed include the ways to lessen the mortality associated with several diseases such as tuberculosis, malaria, and AIDS, the environmental health, and the aspects for the integrated perspective in sanitation, water, and hygiene such as enabling environment, economic incentives and opportunities, and motivation of behavior change.

Electrodes for nitric and nitrous oxide have been on the market for some time, but have not yet been tested for an application in wastewater treatment processes. Both sensors were therefore assessed with respect to their (non)linear response, temperature dependence and potential cross sensitivity to dissolved compounds, which are present and highly dynamic in nitrogen conversion processes (nitric oxide, nitrous oxide, nitrogen dioxide, ammonia, hydrazine, hydroxylamine, nitrous acid, oxygen, and carbon dioxide). Off-gas measurements were employed to differentiate between cross sensitivity to interfering components and chemical nitric oxide or nitrous oxide production. Significant cross sensitivities were detected for both sensors: by the nitrous oxide sensor to nitric oxide and by the nitric oxide sensor to ammonia, hydrazine, hydroxylamine and nitrous acid. These interferences could, however, be removed by correction functions. Temperature fluctuations in the range of ±1 °C lead to artifacts of ±3.5% for the nitric oxide and ±3.9% for the nitrous oxide sensor and can be corrected with exponential equations. The results from this study help to significantly shorten and optimize the determination of the correction functions and are therefore relevant for all users of nitric and nitrous oxide electrodes. [ABSTRACT FROM AUTHOR]

Recent developments in high- and middle-income countries have exhibited a shift from conventional urban water systems to alternative solutions that are more diverse in source separation, decentralization, and modularization. These solutions include nongrid, small-grid, and hybrid systems to address such pressing global challenges as climate change, eutrophication, and rapid urbanization. They close loops, recover valuable resources, and adapt quickly to changing boundary conditions such as population size. Moving to such alternative solutions requires both technical and social innovations to coevolve over time into integrated socio-technical urban water systems. Current implementations of alternative systems in high- and middle-income countries are promising, but they also underline the need for research questions to be addressed from technical, social, and transformative perspectives. Future research should pursue a transdisciplinary research approach to generating evidence through socio-technical "lighthouse" projects that apply alternative urban water systems at scale. Such research should leverage experiences from these projects in diverse socio-economic contexts, identify their potentials and limitations from an integrated perspective, and share their successes and failures across the urban water sector.

Separate collection of urine, which is only 1% of wastewater volume but contains the majority of nitrogen humans excrete, can potentially reduce the costs and energy input of wastewater treatment and facilitate recovery of nitrogen for beneficial use. Ion exchange was investigated for recovery of nitrogen as ammonium from urine for use as a fertilizer or disinfectant. Cation adsorption curves for four adsorbents (clinoptilolite, biochar, Dowex 50, and Dowex Mac 3) were compared in pure salt solutions, synthetic urine, and real stored urine. Competition from sodium and potassium present in synthetic and real urine did not significantly decrease ammonium adsorption for any of the adsorbents. Dowex 50 and Dowex Mac 3 showed nearly 100% regeneration efficiencies. Estimated ion exchange reactor volumes to capture the nitrogen for 1 week from a four-person household were lowest for Dowex Mac 3 (5 L) and highest for biochar (19 L). Although Dowex Mac 3 had the highest adsorption capacity, material costs ($/g N removed) were lower for clinoptilolite and biochar because of their substantially lower unit cost.

Sanitizing human and animal waste (e.g., urine, fecal sludge, or grey water) is a critical step in reducing the spread of disease and ensuring microbially safe reuse of waste materials. Viruses are particularly persistent pathogens and can be transmitted through inadequately sanitized waste. However, adequate storage or digestion of waste can strongly reduce the number of viruses due to increases in pH and uncharged aqueous ammonia (NH3), a known biocide. In this study we investigated the kinetics and mechanisms of inactivation of the single-stranded RNA virus MS2 under temperature, pH and NH3 conditions representative of waste storage. MS2 inactivation was mainly controlled by the activity of NH3 over a pH range of 7.0–9.5 and temperatures lower than 40 °C. Other bases (e.g., hydroxide, carbonate) additionally contributed to the observed reduction of infective MS2. The loss in MS2 infectivity could be rationalized by a loss in genome integrity, which was attributed to genome cleavage via alkaline transesterification. The contribution of each base to genome transesterification, and hence inactivation, could be related to the base pKa by means of a Bronsted relationship. The Bronsted relationship in conjunction with the activity of bases in solution enabled an accurate prediction of MS2 inactivation rates.

Electrodes for nitric and nitrous oxide have been on the market for some time, but have not yet been tested for an application in wastewater treatment processes. Both sensors were therefore assessed with respect to their (non)linear response, temperature dependence and potential cross sensitivity to dissolved compounds, which are present and highly dynamic in nitrogen conversion processes (nitric oxide, nitrous oxide, nitrogen dioxide, ammonia, hydrazine, hydroxylamine, nitrous acid, oxygen, and carbon dioxide). Off-gas measurements were employed to differentiate between cross sensitivity to interfering components and chemical nitric oxide or nitrous oxide production. Significant cross sensitivities were detected for both sensors: by the nitrous oxide sensor to nitric oxide and by the nitric oxide sensor to ammonia, hydrazine, hydroxylamine and nitrous acid. These interferences could, however, be removed by correction functions. Temperature fluctuations in the range of ±1 °C lead to artifacts of ±3.5% for the nitric oxide and ±3.9% for the nitrous oxide sensor and can be corrected with exponential equations. The results from this study help to significantly shorten and optimize the determination of the correction functions and are therefore relevant for all users of nitric and nitrous oxide electrodes.