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Research Project
RecyP – Sustainable production of biofertilizers by recycling phosphorus from wastewater treatment plants
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Publications
Phosphorus concentration and speciation in urban wastewater for potential recovery
Publication . Santos, A. F.; Gando-Fereira, L. M.; Quina, M. J.; Alvarenga, P.
Phosphorus (P) scarcity, jointly with eutrophication problems and water shortage, are forcing urban wastewater treatment plants (WWTP) to redirect their focus to nutrient recov-ery and treated water reuse. However, before implementing any recovery approach, it is neces-sary to understand the problem and its variability. In this scope, this work aims to collect data from different WWTP to assess P concentrations, speciation, and variability in urban wastewater. The analysis revealed high levels of total P, before and after anaerobic digestion, and in the sludge dewatering water (100-400 mg P/L), with about 60-80% of total P in the solu-ble form. Also, in the best-case scenario, soluble reactive P (orthophosphate) accounts for over 50% of soluble total P. Preliminary results showed that it would be possible to recover over 100 kg P/day in a WWTP with about 160,000 p.e.
Urban wastewater as a source of reclaimed water for irrigation: barriers and future possibilities
Publication . Santos, Andreia F.; Alvarenga, Paula; Gando-Ferreira, Licínio M.; Quina, Margarida J.
Water resources are under pressure worldwide, resulting in scarcity and deterioration of
freshwater quality. According to European directives, we could reduce the pressure on water resources in urban areas by increasing the reuse of treated wastewater, reducing the impact on water
bodies, and promoting water recycling through multiple uses of urban wastewater. Besides the need
to address water supply challenges, wastewater treatment systems show environmental stewardship and innovative practices. Using reclaimed water for agricultural irrigation is gaining interest
because of the drought conditions experienced in Europe over the past few years. Furthermore,
using treated wastewater for agricultural irrigation may help to restore nutrients (N and P) to natural biogeochemical cycles. This review highlights the importance of water reuse, current legislation, and existing technologies to implement in wastewater treatment systems to meet the minimum
requirements to produce reclaimed water to reuse in agricultural irrigation.
Urban Wastewater as a Source of Reclaimed Water for Irrigation: Barriers and Future Possibilities
Publication . Santos, Andreia F.; Alvarenga, Paula; Gando-Ferreira, Licínio M.; Quina, Margarida J.
Water resources are under pressure worldwide, resulting in scarcity and deterioration
of freshwater quality. According to European directives, we could reduce the pressure on water
resources in urban areas by increasing the reuse of treated wastewater, reducing the impact on water
bodies, and promoting water recycling through multiple uses of urban wastewater. Besides the need
to address water supply challenges, wastewater treatment systems show environmental stewardship
and innovative practices. Using reclaimed water for agricultural irrigation is gaining interest because
of the drought conditions experienced in Europe over the past few years. Furthermore, using
treated wastewater for agricultural irrigation may help to restore nutrients (N and P) to natural
biogeochemical cycles. This review highlights the importance of water reuse, current legislation,
and existing technologies to implement in wastewater treatment systems to meet the minimum
requirements to produce reclaimed water to reuse in agricultural irrigation.
Phosphorus removal from urban wastewater through adsorption using biogenic calcium carbonate
Publication . Santos, Andreia F.; Lopes, Daniela V.; Alvarenga, Paula; Gando-Ferreira, Licínio M.; Quina, Margarida J.
Phosphorus (P) removal from urban wastewater is increasingly relevant in the wastewater treatment sector. The
present work aims to contribute to the study of the adsorption process as a P removal technology. Biogenic
calcium carbonate from industrial eggshell waste prepared by milling and calcination was used as an adsorbent.
Batch adsorption experiments were conducted using real wastewater with 40 mg P/L (orthophosphate), original
pH 7.33, under stirring conditions (100 rpm). The adsorbent was characterized using SEM-EDS, XRD, and FTIRATR
before and after adsorption. From an initial screening of calcination times (15, 30, 60, and 120 min) and
considering a balance between P removal and energy saving, the adsorbent selected was eggshell calcined at
700 ◦C for 60 min. The Langmuir isotherms describe the experimental data with a maximum adsorption capacity
of 4.57 mg P/g at 25 ◦C. The adsorption process reached equilibrium within 120 min for different dosages (5, 10,
and 20 g/L at 25 ◦C). Batch experiments showed that SO42 , at a concentration of 2689 mg/L reduced the P
adsorption selectivity for dosages ≤10 g/L at 25 ◦C. Characterization of the loaded adsorbent shows that P
adsorption from real wastewater is mostly electrostatic attraction, with the contribution of ligand exchange and
microprecipitation. The adsorption capacity and behavior of the selected adsorbent seem promising for P
removal from urban wastewater compared with other low-cost adsorbents.
Agronomic valorization of sewage sludge: The potential of thermal drying to achieve sanitation and biological stability
Publication . Santos, Andreia F.; Alvarenga, Paula; Gando-Ferreira, Licínio M.
This work aims to contribute to the discussion of using a waste (sewage sludge) to obtain a
valuable product (organic-rich fertilizer), based on a circular economy perspective. The compo-
sition of sewage sludge (SS) was considered, highlighting important characteristics as raw ma-
terial for fertilizer production (e.g., macronutrients, microbiological contamination,
phytotoxicity). Particularly, the biological stability of SS was evaluated measuring the oxygen
uptake rate (OUR) using the Oxitop® method, and the phytotoxicity using germination tests. The
potential of thermal drying to stabilize the SS was evaluated at two temperatures (100 and
130◦C). The results showed that the organic matter (OM), N, and P levels are within the range of
interest for agronomic valorization, while the content of some potentially toxic metals (e.g., Zn
and Cu) may exceed the legal limits. The phytotoxicity assessment showed that raw SS samples
negatively impacted the germination phase. Concerning the biological stability, results showed
that raw anaerobic digested samples were characterized by OUR values above 50 mmol O2/kg
OM.h (the limit for stable SS). Although thermal treatment of SS at 100 and 130◦C eliminated
pathogens and significantly stabilized SS to OUR values below 50 mmol O2/kg OM.h, it was not
enough to reach the limit established for a stable fertilizer (25 mmol O2/kg OM.h). Globally, SS
has potential for soil application, within the scope of circular economy, but it is essential to
control its microbiological contamination and stability.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
Funding Award Number
2020.08213.BD