Combined
coagulation flocculation pretreatment unit for municipal wastewater
Original
article written by Ibrahim M. Ismail, Ahmed S. Fawzy, Nabil M. Abdel-Monem,
Mahmoud H. Mahmoud and Mohamed A. El-Halwany. They are all from the Chemical
Engineering Department, Cairo University and Mathematical and Physics
Department, Faculty of Engineering, Mansoura University, Egypt.
The article was published on ScienceDirect.com on the 5th of
March 2012 and this summary was written on the 18thof November 2018.
The article
starts with the introduction of the situation of Egypt’s urban waterways and
the impact of municipal waste-water. There are problems such as low dissolved
oxygen which impacts the aquatic life by killing fish, blooming algal and
increasing different contaminates. The untreated wastewater contains organic
material, pathogenic microorganisms, heavy metals, nutrients and toxic
compounds making the wastewater environmental and health hazard.
The
ultimate goals are the protection of the environment and public health. The
article tackles the pretreatment side of wastewater management by using
coagulation and flocculation. The chemically enhanced processes are utilized to
improve the efficiency of primary treatment processes and to reduce the costs
of following treatment stages. The aim of the article’s research is to conduct
a study to locate the optimum doses of the used coagulants and study the effect
of different variables affecting the treatment efficiency.
The
general chemical treatment process involves three unit operations of rapid
mixing, flocculation and settling. The chemicals are added in the first step
before mixing and making sure of complete dispersion. Coagulated particles are
brought together by flocculation and the solid materials are the separated in
clarification unit by gravity.
In the
study of the article, they are using a jar tests by using raw sewage of the El
Mansoura governorate wastewater treatment plant. They used alum, ferrous
sulfate, ferric sulfate and lime as their coagulants. We excluded the use of lime
because it causes too much post-treatment.
Based on
their study, they found that use of alum is the optimum coagulant for the
treatment of the sewage at El Mansoura. They proposed the use of combined unit
of coagulation, flocculation and sedimentation designed and operated by
utilizing hydraulic mixing for integration with the existing sewage treatment
plants to reduce the load of the following stages.
Here’s a
link to the article in question: https://www.sciencedirect.com/science/article/pii/S2090123211001214
Three-dimensional (3D) palladium-zinc oxide nanowire
nanofiber as photo-catalyst for water treatment
Original article written by Jungsu Choi, Sophia Chan,
Hyunjong Joo, Heejae Yang and Frank K. Ko
The original article was published in Water
Research issue 101, on 26th of May 2016.
The article focuses on filtration methods of organic
matter (OM) in water treatment. The most common methods of removing organic
matter from wastewater are oxidative chemicals, UV-light treatment and
photocatalysis. The studies method uses photocatalysis, where a photocemical
oxidation reaction between the semiconductors metal oxide surfaces and the
organic matter occurs.
There are several promising photo-catalysts such as
titanium dioxide (TiO2), iron(III) oxide (Fe2O3),
zirconia, zinc oxide, vanadium oxide, niobium pentoxide and tungsten trioxide,
but they aren't very cost-efficient or they are problematic to post-process.
Zinc Oxide Nano Wires (ZNW) are used as the
photocatalyst, because they are efficient and affordable. In the study, they
synthesized a three-dimensional palladium-ZNW membrane via electrospinning. The
spesific removal rate of OM in ZNW is 0,0247, as compared to a traditional ZnO
structure, that has the SSR ranging from 0,0005 to 0,0188. By doping the ZNW
nanofibers with palladium, the photocatalytic efficiency and COD removal rate
increased by 30%.
The Pd/ZNW nanofibers provide more efficient
photocatalytic reactions than only ZNW fibers, but the base nanofiber structure
is the most important factor in effective photodecomposition of organic matter.
Handling and service of these membrane filters are easier than other
photocatalysts, that are usually in a powdered form or as grains.
Here’s a link to the article in question: https://www.sciencedirect.com/science/article/pii/S0043135416303979
Magnetic
water treatment: A review of the latest approaches
Original
article written by Emil Chibowski and Aleksandra Szczes from the
Department of Physical Chemistry in Maria Curie-Sklodowska University, Lublin,
Poland.
The
original article was published in Chemosphere issue 203, on
24th of March 2018.
The last
article reviews opportunities of using magnetic forces in water treatment. The
review is based on controversial theories and studies, as the effects of
magnetic fields in aqueous solutions aren’t fully understood.
Originally
the need to understand magnetic field (MF) effects came from stem cell research
and therapy, which created the need for measurable parameters inside an aqueous
substance, for example, a stem cell. The most common measured parameters in MF
research are: exposure time to MF, nucleation and precipitation times of
chemicals, coagulation, polymorphism of crystals, particle dispersion,
electrical conductivity, surface tension, viscosity, pH changes and
diffusivity.
The most
recognized mechanisms of MF effects in a solution are the ion mechanism and
surface mechanism. The ion mechanism states how the MF acts on the ions
dissolved in water, such as changing a chemicals nucleation process, ion
hydration or cluster transformation. A slower nucleation and coagulation of a
precipitate could be used in water treatment processes, such as lime softening.
In surface mechanism, MF effects on the surface charges and field action of the
particulates.
Both MF
mechanisms, as well the as the Lorenz force have been concluded to have actions
on particle precipitation in aqueous solutions. The review pointed that the MF
has complex and variable effects, that are not researched enough. Due to the
lack of consistent theory of field mechanism action, a precise and effective
magnetic force treatment of water isn’t feasible yet.
I really like your blog and this is a very interesting post. During your project, do you think that you will perform any of the water treatment methods you have written about?
ReplyDeleteHey Anna! We will probably evaluate different methods and if the methods in the articles work with our ideas, we will use them for sure.
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