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Nature-based solutions for wastewater treatment and bioenergy recovery: A comparative Life Cycle Assessment

DOI: 10.1016.2023.163291

The aim of this study was to assess the environmental impacts of up-flow anaerobic sludge blanket (UASB) reactors coupled with high rate algal ponds (HRAPs) for wastewater treatment and bioenergy recovery using the Life Cycle Assessment (LCA) methodology. This solution was compared with the UASB reactor coupled with other consolidated technologies in rural areas of Brazil, such as trickling filters, polishing ponds and constructed wetlands. To this end, full-scale systems were designed based on experimental data obtained from pilot/demonstrative scale systems. The functional unit was 1 m3 of water. System boundaries comprised input and output flows of material and energy resources for system construction and operation. The LCA was performed with the software SimaPro®, using the ReCiPe midpoint method. The results showed that the HRAPs scenario was the most environmentally friendly alternative in 4 out of 8 impact categories (i.e. Global warming, Stratospheric Ozone Depletion, Terrestrial Ecotoxicity and Fossil resource scarcity). This was associated with the increase in biogas production by the co-digestion of microalgae and raw wastewater, leading to higher electricity and heat recovery. From an economic point of view, despite the HRAPs showed a higher capital cost, the operation and maintenance costs were completely offset by the revenue obtained from the electricity generated. Overall, the UASB reactor coupled with HRAPS showed to be a feasible nature-based solution to be used in small communities in Brazil, especially when microalgae biomass is valorised and used to increase biogas productivity.

Wastewater-based epidemiology for preventing outbreaks and epidemics in Latin America–Lessons from the past and a look to the future

DOI: 10.1016.2022.161210

Wastewater-based epidemiology (WBE) is an approach with the potential to complement clinical surveillance systems. Using WBE, it is possible to carry out an early warning of a possible outbreak, monitor spatial and temporal trends of infectious diseases, produce real-time results and generate representative epidemiological information in a territory, especially in areas of social vulnerability. Despite the historical uses of this approach, particularly in the Global Polio Eradication Initiative, and for other pathogens, it was during the COVID-19 pandemic that occurred an exponential increase in environmental surveillance programs for SARS-CoV-2 in wastewater, with many experiences and developments in the field of public health using data for decision making and prioritizing actions to control the pandemic. In Latin America, WBE was applied in heterogeneous contexts and with emphasis on populations that present many socio-environmental inequalities, a condition shared by all Latin American countries. This manuscript addresses the concepts and applications of WBE in public health actions, as well as different experiences in Latin American countries, and discusses a model to implement this surveillance system at the local or national level. We emphasize the need to implement this sentinel surveillance system in countries that want to detect the early entry and spread of new pathogens and monitor outbreaks or epidemics of infectious agents in their territories as a complement of public health surveillance systems.

Quantification of SARS-CoV-2 in wastewater samples from hospitals treating COVID-19 patients during the first wave of the pandemic in Brazil

DOI: 10.1016.2022.160498

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Influence of salt addition to stimulating biopolymers production in aerobic granular sludge systems

DOI: 10.1016.2022.137006

The influence of salt addition to stimulating biopolymers production in aerobic granular sludge (AGS) systems was evaluated. The control systems (R1: acetate and R2: propionate) initially obtained less accumulation of mixed liquor volatile suspended solids (MLVSS), indicating that the osmotic pressure in the salt-supplemented systems (R3: acetate and R4: propionate) contributed to biomass growth. However, the salt-supplemented systems collapsed between days 110 and 130 of operation. R3 and R4 showed better performance regarding nutrients removal due to the greater abundance of nitrifying and denitrifying bacteria and phosphate-accumulating organisms. Salt also contributed to the higher production of biopolymers such as alginate-like exopolymers (ALE) per gram of volatile suspended solids (VSS) (R1: 397 mgALE∙gVSS−1, R2: 140 mgALE∙gVSS−1, R3: 483 mgALE∙gVSS−1, R4: 311 mgALE∙gVSS−1). Amino acids like tyrosine and tryptophan were better identified in extracellular polymeric substances extract from salt-operated reactors. This study brings important results in the context of resource recovery by treating saline effluents.

Influence of operating regime on resource recovery in aerobic granulation systems under osmotic stress

DOI: 10.1016.2023.128850

Aerobic granular sludge (AGS) systems have great potential for biopolymers recovery, especially when subjected to adverse conditions. This work aimed to study the production of alginate-like exopolymers (ALE) and tryptophan (TRY) under osmotic pressure in conventional and staggered feeding regimes. The results revealed that systems operated with conventional feed accelerated the granulation, although less resistant to saline pressures. The staggered feeding systems favored better denitrification conditions and long-term stability. Salt addition gradient increase influenced biopolymers’ production. However, staggered feeding, despite decreasing the famine period, did not influence the production of resources and extracellular polymeric substances (EPS). Sludge retention time (SRT), which was not controlled, proved to be an important operational parameter with negative influences on biopolymers’ production in values greater than 20 days. Thus, the principal component analysis confirmed that the production of ALE at low SRT is related to better-formed granules with good sedimentation characteristics and good AGS performances.

Start-up strategies to develop aerobic granular sludge and photogranules in sequential batch reactors

DOI: 10.1016.2022.154402

In this study, start-up strategies to develop conventional aerobic granular sludge (AGS) and algal aerobic granular sludge (AAGS) (photogranules), were investigated. The granulation experiment was conducted in four sequencing batch reactors (SBR), of which two were conventional SBRs (RC1, RC2) used as control, and two were photo-SBRs (R1, R2). R1 and RC1 were operated with a 40-min feeding during the reactors´ anaerobic cycle period, whereas R2 and RC2 with a 60-min feeding. All the reactors were operated in two phases with a C:N = 4:1 in Phase I and 8:1 in Phase II. In Phase I, AGS in RC1 and RC2 was formed 15 days before the AAGS development in R1 and R2. However, the AAGS generally presented better stability and higher diameter. On the other hand, AGS presented greater abundance of extracellular polymeric substances producing organisms, such as Xanthomonadacea and Rhodocyclaceae. Chemical oxygen demand (COD) and NH4+-N removal efficiencies were similar in all the four reactors of approximately 70% and 60%, respectively. In this phase, despite the good biomass structure, the reactors were not able to completely oxidize the high influent concentration of NH4+-N (100 mg.L−1) and COD (400 mg.L−1). This can be associated to the short time of the aerobic phase and low biomass content. In Phase II in all the reactors, a good increase in COD and NH4+-N removal efficiencies to values above 95% and 93%, respectively, was achieved under a higher C:N ratio of 8 with lower influent concentration of NH4+-N (50 mg.L−1). The 60-min anaerobic feeding period in R2 and RC2 resulted in greater removal efficiency of nitrogen, confirming that small variation on cycle periods can affect the biomass composition; the biomass presented more compact granules and larger diameters under 60 min-feeding when compared with those obtained with 40 min-feeding in Phase I.

Formation and stability of aerobic granular sludge in a sequential batch reactor for the simultaneous removal of organic matter and nutrients from low-strength domestic wastewater

DOI: 10.1016.2022.156988

Simultaneous removal of organic matter, nitrogen, and phosphorus, via simultaneous nitrification and denitrification (SND) and enhanced biological phosphorus removal processes, was evaluated in a pilot-scale sequential batch reactor. The focus was on granule’s morphology, stability, microbiological composition, and reactor performance while treating diluted domestic wastewater with total chemical oxygen demand (CODt) of ≈ 200 mg.L-1. The applied organic loading rate was 0.9 ± 0.3 kg CODt.m−3.d−1 in the experiment. Aerobic granular sludge developed gradually. After 87-day operation, granules (diameter ≥ 0.2 mm) were ≥ 50 % of the biomass, and after 168 days, complete granulation was obtained (≥ 80 % of biomass). In the third period (days 168–247, complete granulation), mixed liquor biomass reached a volatile suspended solids (VSS) concentration of 1.2 ± 0.3 g VSS.L−1, with the granules remaining stable until the experimental end. In this period, low effluent concentrations of COD, nitrogen (NH4+-N, NO2-N and NO3-N) and phosphate (PO43—P) were obtained (mg.L−1): 36 ± 11; 4 ± 5; 3 ± 3, 4 ± 5; and 0.9 ± 0.4, respectively. COD, NH4+-N, and PO43−-P removal efficiencies (%) were 80 ± 11; 83 ± 20; and 55 ± 24, respectively. Heterotrophic nitrification and SND were observed, resulting in a process efficiency of 31 % even with dissolved oxygen applied to saturation. The phosphate removal was mainly attributed to denitrifying phosphorus accumulating organisms. Pseudomonas, the dominant genus found, acted in nitrogen and phosphorus removal. Pseudoxanthomonas also assisted in phosphorus removal. Bacterial communities in the flocs (≈ 20 % of biomass) during the last period were similar to those in the granules; therefore, they constituted the basis for granule formation, directly contributed to the simultaneous good removal of organic matter and nutrients.

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