Integrating food waste management into urban wastewater treatment: Economic and environmental impacts.

Food waste is the main component of municipal solid waste (MSW) and its sustainable management is a global challenge. Co-treatment of food waste and urban wastewater in wastewater treatment plants (WWTPs) could be a plausible management strategy to reduce the MSW amount that is disposed in landfills, while converting its organic fraction into biogas in the WWTP. However, the increased organic load in the wastewater influent would impact the capital and operating costs of the WWTP, mainly due to the increase in sludge production. In this work, different scenarios for co-treatment of food waste and wastewater were studied from both economic and environmental perspectives. These scenarios were designed based on different sludge disposal and management options. The results showed that the co-treatment of food waste and wastewater would be more environmentally friendly than their separate treatment, but its economic feasibility strongly depends on the ratio between the management costs of MSW and sewage sludge.

Drinking Water Supply in the Region of Antofagasta (Chile): A Challenge between Past, Present and Future.

Since the mid-nineteen century, when the first mining companies were established in the region of Antofagasta to extract saltpeter, mining managers and civil authorities have always had to face a number of problems to secure a water supply sufficient for the development of industrial activities and society. The unique features of the region, namely the scarcity of rainfall, the high concentration of arsenic in freshwaters and the increasing pressure of the mining sector, have made the supply of drinking water for local communities a challenge. In the 1950s, the town of Antofagasta experienced a serious drinking water crisis. The 300 km long aqueduct starting from the Toconce catchment, opened in 1958, temporarily ended this shortage of drinking water but created an even more dramatic problem. The concentration of arsenic in the water consumed by the population had grown by approx. ten times, reaching the value of 0.860 mg/L and seriously affecting people's health. The water treatment plants (WTPs) which were installed starting from the 1970s in the region (namely the Old and New Salar del Carmen in Antofagasta and Cerro Topater in Calama, plus the two recent desalination plants in Antofagasta and Tocopilla), have ensured, since 2014, that the drinking water coverage in the urban areas was practically universal (>99.9%). However, the rural areas have continued to experience significant shortcomings regarding their capacity to ensure the quality and continuity of the water supply service in the long run. Presently, approx. 42% of the rural population of the region of Antofagasta does not have a formal supply of drinking water. The recent amendments to the Chilean Water Code (March 2022) and the interventions carried out in the framework of the Agua Potable Rural (APR) program were intended to reduce the socio-ecological inequalities due to the lack of drinking water in the semi-concentrated and isolated rural population.

Vermiproductivity, maturation and microbiological changes derived from the use of liquid anaerobic digestate during the vermicomposting of market waste.

Recently, it has been suggested that the liquid fraction of anaerobic digestate, derived from the treatment of wastewater and solid wastes, could be used in vermicomposting as a solution to its disposal, and even for its valorization. Nevertheless, the literature does not provide enough information about its impact on the process of vermicomposting itself and on the final quality of the end-product. In this study, the effect of different doses of digestate in the vermicomposting process treating market waste is assessed measuring earthworm population dynamics, the bacterial community succession present in the vermibeds, as well as maturation and the end-quality of the vermicompost. Our results show that the addition of liquid digestate to the vermibeds increased the earthworms biomass, i.e. 71%, 94% and 168% in control, and vermibeds with 30% and 60% digestate, respectively. Further, the increase in the amount of N in the vermicompost decreased as the digestate addition increased, i.e. 75%, 8%, 3%. The maturity achieved was high in all treatments as shown by the C/N ratio, 7.98, 7.40 and 10.20, and the high seed germination rate, above 90%. Finally, the succession of the microbial community was not disturbed and compositional stabilization was reached after 92 days.

Predicting Accumulation of Intermediate Compounds in Nitrification and Autotrophic Denitrification Processes: A Chemical Approach.

Nitrification and sulfur-based autotrophic denitrification processes can be used to remove ammonia from wastewater in an economical way. However, under certain operational conditions, these processes accumulate intermediate compounds, such as elemental sulphur, nitrite, and nitrous oxide, that are noxious for the environment. In order to predict the generation of these compounds, an analysis based on the Gibbs free energy of the possible reactions and on the oxidative capacity of the bulk liquid was done on case study systems. Results indicate that the Gibbs free energy is not a useful parameter to predict the generation of intermediate products in nitrification and autotrophic denitrification processes. Nevertheless, we show that the specific productions of nitrous oxide during nitrification, and of elemental sulphur and nitrite during autotrophic denitrification, are well related to the oxidative capacity of the bulk liquid.

Biorefinery of cellulosic primary sludge towards targeted Short Chain Fatty Acids, phosphorus and methane recovery.

Cellulose from used toilet paper is a major untapped resource embedded in municipal wastewater which recovery and valorization to valuable products can be optimized. Cellulosic primary sludge (CPS) can be separated by upstream dynamic sieving and anaerobically digested to recover methane as much as 4.02 m3/capita·year. On the other hand, optimal acidogenic fermenting conditions of CPS allows the production of targeted short-chain fatty acids (SCFAs) as much as 2.92 kg COD/capita·year. Here propionate content can be more than 30% and can optimize the enhanced biological phosphorus removal (EBPR) processes or the higher valuable co-polymer of polyhydroxyalkanoates (PHAs). In this work, first a full set of batch assays were used at three different temperatures (37, 55 and 70 °C) and three different initial pH (8, 9 and 10) to identify the best conditions for optimizing both the total SCFAs and propionate content from CPS fermentation. Then, the optimal conditions were applied in long term to a Sequencing Batch Fermentation Reactor where the highest propionate production (100-120 mg COD/g TVSfed·d) was obtained at 37 °C and adjusting the feeding pH at 8. This was attributed to the higher hydrolysis efficiency of the cellulosic materials (up to 44%), which increased the selective growth of Propionibacterium acidopropionici in the fermentation broth up to 34%. At the same time, around 88% of the phosphorus released during the acidogenic fermentation was recovered as much as 0.15 kg of struvite per capita·year. Finally, the potential market value was preliminary estimated for the recovered materials that can triple over the conventional scenario of biogas recovery in existing municipal wastewater treatment plants.

Precipitação química de estruvita: Recuperação de nutrientes em reator cônico de leito fluidizado utilizando magnésia industrial de baixo custo / Chemical precipitation of struvite: Nutrients recovery in conic fluidized bed reactor using a low-cost industrial magnesia compound

O processo físico-químico da precipitação de estruvita é uma técnica que apresenta elevado potencial na remoção de nutrientes, a partir de diferentes tipologias de efluentes. O presente estudo teve por objetivo a avaliação de um composto industrial com elevado teor de magnésia e baixo custo como fonte reagente alternativa de magnésio e alcalinidade necessários ao processo de precipitação, tornando-o economicamente viável com a redução de gastos despendidos com químicos. Suspensões de Mg(OH)2 foram obtidas e tiveram desempenho avaliado em função da remoção de nutrientes, a partir de um efluente sintético rico em N-NH4+ e P-PO43-, e qualidade dos cristais gerados, com a identificação do mineral de interesse - estruvita. O experimento foi realizado em escala laboratorial utilizando reator cônico de leito fluidizado operado em semi-contínuo. O adequado controle operacional do pH (8,0-8,5) pela adição automatizada da suspensão de Mg(OH)2 possibilitou uma considerável remoção de P-PO43-, que atingiu valor médio igual a 93,5%. Os sólidos recuperados no processo apresentaram pureza de, aproximadamente, 84% de estruvita.

The physico-chemical process of struvite precipitation is a technique that demonstrates a high potential in nutrients recovery from different kinds of wastewaters. This study aimed to evaluate the use of a low cost industrial compound with high magnesia content as alternative reagent source of magnesium ions and alkalinity required for precipitation. It was a strategy to turn the process economically viable and reduce the chemical costs. Mg(OH)2slurries were obtained and evaluated regarding the nutrients recovery from a synthetic wastewater rich in NH4+-N and PO43--P and the quality of the generated crystals with the identification of the mineral of interest - the struvite. The experiment was performed in laboratory scale using a conic fluidized bed reactor in a semi-continuous operation. The proper pH control (8.0-8.5) by the automated addition of Mg(OH)2slurry allowed considerable PO43--P removal equal to 93.5%. The recovered solids from the process showed purity of approximately 84% of struvite.