2,114 research outputs found
Qualidade de vida: nutrição, higiene e segurança dos alimentos.
bitstream/item/128275/1/EMA-5-VIDA.pdfProjeto Minibibliotecas
Performance assessment of micropollutants removal from water using advanced oxidation processes
In a global climate change scenario, reliable access to clean and safe water for all remains a great
worldwide challenge for the twenty first century, as one of the most ambitious targets of several Sustainable
Development Goals (SDG) established in the UN Agenda 2030. The increasing presence in the urban aquatic
ecosystems of priority pollutants and contaminants of emerging concerning (CECs) have brought new
challenges to the existing water treatment systems (WTS) concerning with public health protection and the of
drinking water sources preservation. Advanced oxidation processes (AOPs) have been widely studied because
of their potential as a complementary or alternative process to conventional wastewater treatment. Several
AOPs using nanomaterials as photocatalyst can be particularly effective in the degradation of many toxic
micropollutants, and enhance the multifunctionality, versatility and sustainability of WTS.
This work presents a synthesis of the major results obtained in several pilot and lab-scale studies aiming to
assess the performance of different low-cost catalytic processes used for antibiotic and pesticide removal. For
each photo-oxidation reactors, different test scenarios are defined in order to evaluate the effects of several
abiotic and hydraulic parameters on process kinetics and removal efficiencies.
The experimental results were very promising, because antibiotic removal efficiencies achieved the maximum
value of 96% for the photo-oxidation by water columns with suspended TiO2 nanoparticles, and 98% for the
photocatalytic filtration performed by a porous medium coated with TiO2. In the photoelectrocatalytic reactor,
the atrazine concentration has been fully removed for reaction times between 35 and 95 minutes.(undefined
HEAT EXCHANGER NETWORK SYNTHESIS CONSIDERING CHANGING PHASE STREAMS
The Pinch Design Method was developed considering one-phase streams, with constant
specific heats (Cp) throughout streams temperature ranges. Its first stage, the determination
of utilities targets and pinch point (PP), is ruled by the number of streams, their temperatures
and MCp. But, for changing phase streams, the usual description of the Cp behavior by a
constant value can lead to errors in this stage and, hence, in the synthesis one. This work
proposes a procedure to deal with these streams and discusses its results through an example
involving multicomponent streams. First, bubble (BP) and dew (DP) points of the streams
are estimated. Then, changing phase streams are split into sub-streams, using BP and DP
as bounds. For each one, an effective Cp is estimated as the division of the enthalpy
change by the respective temperature difference. Results obtained show significant changes
on the PP, utilities targets and network proposed structure
Arsenic removal from drinking water by advanced filtration processes
All over the world the presence of arsenic in water sources for human consumption has been raising great concern in terms of public health since many epidemiologic studies confirm the potential carcinogenic effect
of arsenic. Because arsenic removal is the most frequent option for safe drinking water, the development of more efficient and sustainable technologies is extremely important.
Membrane separation processes are suitable for water treatment because they can provide an absolute barrier for bacteria and viruses, besides removing turbidity and colour. Their application is a promising
technology in arsenic removal since it does not require the addition of chemical reagents nor the preliminary oxidation of arsenite required in conventional treatment options. However, since membrane technologies
such as reverse osmosis can be a very expensive and unsustainable treatment option for small water supply systems, it becomes crucial that alternative methods are developed.
This work presents a few conclusions based on a laboratorial study performed to evaluate the efficiency of arsenic removal using ultrafiltration, microfiltration and solar oxidation processes under different experimental conditions for relevant parameters. The results showed removal efficiencies higher than 90%
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