FUTURE WORK FOR THE DEVICE
1. GENERAL PROPOSAL
Considering aspects of the importance of taking data in real time, it is essential to be able to carry
arsenic measurements in situ, and since well or wastewater waters consist of different composition
characteristics (Total solids, and other ionic agents that may interfere with the detection of arsenic)
(Escalera Vásquez, 2014)a pretretting process must be carried out before measuring arsenic, with this
process we will be able to carry out the in situ measurements of arsenic without any interference from
Since on average wastewater or well water contains high amounts of total solids, there must be a first
for the filtration of particulate materials, which we will call a primary filter, we will also require
absorbent for ions that can compete with Arsenic or that may interfere with the measurement of Arsenic,
thus, a second filter is required for the removal of other ionic agents.
After the pre-treatment process, the water sample will require an incubator, because the lyophilized
biosensor in filter paper must be immersed in the water sample to be sensed, and then incubated for at
18 hours at 36°C, for the generation of chromoproteins, which will give a characteristic color, which
allow us, thanks to our device, measure arsenic concentration.
2. EQUIPMENT DESIGN
2.1 PRIMARY FILTER DESIGN
The objective of the initial filter is the removal of foreign bodies with respect to the observation
analyte, without altering the presence of this, so that it can be identified in filter 2. For this
purpose, the bibliographic review (Escalera Vásquez, 2014) studied indicates that the primary filter
must retain a significant percentage of large substances such as total solids and others, on the other
hand, in this filter micro and nanoparticulate material is deposited, others of biological and chemical
material in smaller quantities.
The primary filter will be made up of a small hollow cylinder made of polypropylene with holes along the
surface to allow passage to the flow of water. The filter surface would allow a coating of 3.5cm long by
0.8cm wide of a stainless steel mesh that contributes to the retention of larger particulate matter
(Reyes, 2014). The filter size parameters are detailed below:
Table 1. General parameters of the
Source: Adapted from (Reyes, 2014)
Figure 1 Primary filter design: stainless steel filter N°100
Source : Own elaboration
A mesh will be needed to coat the primary filter whose material must be stainless steel N°100 which
ensures high corrosion resistance and consequently long life. These meshes will be used for: i) their
ease of cleaning and maintenance, ii) filtration capacity, iii) resistance to oxidation in the presence
of acids or other chemical agents (Reyes, 2014). The characteristics of this mesh are detailed below:
Table 2. Specific parameters of mesh
|D: Wire diameter in mm
|w: Distance between 2 contiguous wires
Source: Adapted from(Reyes,
A second stage of the primary filter will consist of a cylindrical filter with an adsorbent material of
micro and nanoparticles as well as chemical and biological agents. For the selection of this material, a
table was made to be able to select the best material:
Table 3. Material comparison for the
||i) Absorbent material that removes organic matter(BOD5), total suspended solids
(OSH), organic compounds among others, ii) Easy access in the market
||i) Can remove As and other heavy metals.
ii) Saturation in the pores, decreasing the efficiency of the system.
||i) Absorbent, ii) High tear resistance, iii) Smooth texture, iv) Does not accumulate
static electricity, v) Does not retain metals, vi) Degradable, vii) Low cost.
||ii) Not reusable
|Paper or fabric filters
||i) Porosity, ii) High solids holding capacity iii) Moisture resistant, iv) Flow
Source: Adapted from(Reyes,
Given the characteristics mentioned in the table above, a matrix of commercial cotton fibers was
selected. The criteria used for this selection are as follows:
i) It is an absorbent material of great utility in the retention of solids for water samples taken in
situ, ii) can be functionalized for the selective retention of heavy metals; iii) does not have
retention of As (when it is not activated as will be demonstrated),iv) is a low-cost material with easy
access in the market,v) is easy to handle vi) is a material of easy degradation, the latter being one of
the main criteria for selecting materials for the configuration of the pretreation system since it has a
low environmental impact on living beings.
According to the results obtained by (Reyes, 2014),the effectiveness of cotton fibers as a material to
filter water in a first phase is verified, without changing or modifying the arsenic concentration
values and contributing to the retention of ionic species such as mercury and lead. It is also worth
mentioning that it retains a significant amount of particulate matter, but it is insufficient to
eliminate the interference factors, so it is necessary to act on a second filter that we call secondary.