Implementation of Biofilters with Earthworms as a Sustainable
Alternative for Wastewater Treatment in Slaughterhouses
Implementación de
biofiltros con lombrices como alternativa sostenible para tratamiento de aguas
residuales en camales
José Gerardo León Chimbolema1
Published
Instituto Tecnológico Corporativo Edwards DemingQuito - Ecuador Periodicity April - June Vol. 1, Num. 25, 2025 pp. 121-133 http://centrosuragraria.com/index.php/revista Dates of receipt Received: March 12, 2025 Approved: March 30, 2025 Correspondence author Creative Commons License Creative Commons License,
Attribution-NonCommercial-ShareAlike
4.0 International.https://creativecommons.org/licenses/by-nc-sa/4.0/deed.es
[1] Doctor en Química, Máster en protección Ambiental.
Docente investigador. Escuela Superior Politécnica de Chimborazo https://orcid.org/0000-0001-9202-8542
Key words: biofilter, earthworms, Eisenia foetida, wastewater, slaughterhouse, efficiency,
sustainability.
Resumen: La contaminación del agua por aguas residuales
provenientes de camales es un problema ambiental que afecta la salud pública y
los ecosistemas, especialmente en zonas con limitados recursos para
tratamientos convencionales. Esta investigación evaluó la eficiencia de un
biofiltro con lombrices rojas californianas (Eisenia foetida) para tratar las
aguas residuales del Camal Municipal de Pelileo, Ecuador. Se diseñó y construyó
un biofiltro con capas de piedra bola, grava y arena, complementado con un
lecho filtrante de aserrín, viruta y humus donde habitan las lombrices
adaptadas al agua residual. Durante tres semanas se analizaron parámetros
fisicoquímicos como pH, conductividad, color, turbidez, nitrógeno en formas de
nitritos y nitratos, fosfatos, demanda química y bioquímica de oxígeno (DQO y
DBO5), además de sólidos totales y disueltos, antes y después del tratamiento.
Los resultados mostraron una reducción significativa de estos contaminantes,
logrando una eficiencia promedio del 74.87%, con picos de hasta 95% en algunos
parámetros. El biofiltro operó eficazmente sin producir lodos y con bajo costo
de mantenimiento. Asimismo, el agua tratada cumplió con los límites máximos
permisibles según la normativa ambiental vigente, validando el sistema como una
alternativa sostenible y económica. Se concluye que el biofiltro con lombrices es
una solución viable para el tratamiento de aguas residuales en camales,
recomendándose su optimización para ampliar su aplicación en otras industrias
con carga orgánica elevada.
Palabras clave: biofiltro, lombrices, Eisenia foetida, aguas residuales, camal, eficiencia,
sostenibilidad.
Introduction
Water
pollution caused by industrial wastewater, particularly in slaughterhouses or
meat processing plants, is a serious environmental problem that affects both
public health and the integrity of surrounding ecosystems (Gamarra, 2021;
Landeta, 2019). This wastewater contains high levels of organic matter, fats,
suspended solids, nutrients such as nitrogen and phosphorus, as well as
chemical compounds derived from the slaughter and cleaning of animals, which,
if not properly treated, generate severe negative impacts, such as
eutrophication, proliferation of pathogens, and contamination of water sources
(Soto et al., 2020; Rodríguez, 2021). The problem is exacerbated in rural areas
and developing countries, where conventional treatment infrastructure is limited
by high costs and complex technical requirements (Salazar, 2005; Bermúdez,
2019).
Traditional
wastewater treatment methods, although effective, often involve
energy-intensive processes, skilled labor, and generate by-products such as
sludge that require special handling and disposal (Muñoz, 2009; Manrique &
Piñeros, 2016). For this reason, the search for alternative technologies that
are environmentally sustainable, economical, and easy to operate has become
very important. In this context, biofilters based on the action of Californian
red worms (Eisenia foetida) have emerged as an innovative solution for the
biological treatment of wastewater with high organic loads (Arora &
Saraswat, 2021; Misal & Mohite, 2017).
The system
known as the Tohá worm filter or biofilter is based on the ability of worms to
degrade organic matter in a controlled environment, combined with a filter
medium composed of layers of stone, gravel, sand, and organic substrates such
as sawdust and wood shavings, which facilitate microbial activity and physical
filtration (Government of Chile CONAMA, n.d.; Bermúdez, 2019). f.; Bermúdez,
2019). This natural process significantly reduces contaminating parameters such
as biochemical and chemical oxygen demand (BOD and COD), nitrogen, phosphorus,
suspended solids, and turbidity, without generating sludge or odors, with low
operating costs and minimal maintenance (Pérez & Carrasco, 2019; Qiu et
al., 2016).
The worm
Eisenia foetida is particularly suitable for this purpose due to its high
adaptability to different environmental conditions, reproduction rate, and
efficiency in transforming organic waste into humus, a valuable by-product that
can be used as a natural fertilizer (Coronel, 2015; Liberio, 2019). Recent
studies have demonstrated the technical and economic viability of using
vermicomposting in different industries, including agro-industrial, dairy,
meat, and fishing, achieving reductions in organic matter of over 80% and
guaranteeing the quality of the effluent according to local and international
regulations (Bravo, 2019; Cabrera et al., 2022; Maza, 2017).
Furthermore,
the sustainability of this technology is evident in its low environmental
impact, as it does not require chemical inputs, consumes little energy, and
allows the reuse of treated water for irrigation or industrial processes,
promoting the circular economy and the conservation of water resources (Biswas,
2021; Manyuchi et al., 2017). In Ecuador, this alternative is particularly
relevant due to the need to improve wastewater management in rural
slaughterhouses and industrial plants, where access to conventional
technologies is limited and inadequate effluent management has led to social
conflicts and environmental degradation (GAD Ibarra, 2018; Rodríguez, 2021).
This study
focused on evaluating the efficiency of a worm biofilter for treating
wastewater from the Pelileo Municipal Slaughterhouse, analyzing the reduction
of key pollutant parameters and verifying compliance with current environmental
regulations (TULSMA). A system adapted to local conditions was designed,
environmental variables were monitored for the adaptation of the worms, and
physicochemical analyses were carried out over a period of three weeks.
This work
contributes to the body of knowledge on clean technologies applied to
environmental management in the meat industry, offering a viable alternative
for improving water quality and mitigating water pollution in rural areas. It
also emphasizes the need to continue optimizing these systems, adjusting
hydraulic retention times and filter materials in order to maximize efficiency
and promote their adoption on a commercial and community scale.
Methodology
This
study focused on evaluating the efficiency of a biofilter with Californian red
worms (Eisenia foetida) for treating wastewater
generated at the Pelileo Municipal Slaughterhouse in
Ecuador. To this end, an experimental biofilter was designed and constructed
consisting of a stratified tank, taking into account hydraulic and structural
parameters appropriate for the volume and flow rate of the wastewater to be
treated. The biofiltration system consisted of three main layers: a base of
approximately 10 cm of pebbles for support and drainage; an intermediate layer
of gravel with variable grain sizes that facilitates the formation of microbial
biofilm; and a surface layer of fine sand for the retention of suspended
solids. On top of this last layer, an organic bed consisting of a mixture of
sawdust, wood shavings, and humus was placed, which served as a substrate and
food source for Eisenia foetida worms. The
tank was equipped with a water distribution and collection system using
vertically arranged PVC pipes, which allowed uniform irrigation of the
wastewater over the filter surface and the evacuation of the treated water to a
storage tank, thus avoiding stagnation points and facilitating system
maintenance.
To ensure
the biological effectiveness of the biofilter, the worms were subjected to an
adaptation process prior to direct contact with the slaughterhouse wastewater.
During this phase, critical environmental variables were carefully controlled,
such as temperature (optimum range between 18 and 25 °C), pH (6.5 to 8.5), and
substrate moisture, conditions that favor the survival, metabolic activity, and
reproduction of Eisenia foetida. These parameters
were monitored periodically throughout the experimental period to maintain
stable conditions and prevent mass mortality of worms, which could negatively
affect the efficiency of the treatment.
Wastewater
sampling was carried out weekly for three consecutive weeks, taking
representative samples from both the influent and effluent of the biofilter,
following standardized protocols to avoid external contamination. The samples
were analyzed in a certified laboratory to measure key physicochemical
parameters such as pH, electrical conductivity, color, turbidity, nitrogen
concentrations in the form of nitrites and nitrates, phosphates, chemical and
biochemical oxygen demand (COD and BOD5), and total and dissolved solids. These
indicators made it possible to evaluate the pollutant load and the efficiency
of the biofiltration process.
Likewise,
the inflow and outflow of wastewater were measured using timing techniques with
a stopwatch and calibrated containers, which made it possible to calculate the
hydraulic retention time (HRT). The latter is a fundamental parameter that
determines the period during which the water remains in contact with the filter
bed, directly impacting the biological degradation of organic matter. Finally,
the concentrations of pollutants before and after treatment were compared to
determine the percentage removal efficiency, verifying that the final values
complied with the maximum permissible limits established by current
environmental regulations (TULSMA).
Throughout
the process, periodic maintenance activities were carried out, including manual
aeration of the filter bed, mixing the organic substrate to prevent compaction
and ensure permeability, humidity control to maintain optimal conditions for
the worms, and removal of accumulated solid waste that could obstruct the flow.
These practices ensured the operational stability and continuous performance of
the biofilter, guaranteeing its effectiveness in reducing the organic load and
other contaminants present in the slaughterhouse wastewater.
Results
The
wastewater generated by the Pelileo Municipal
Slaughterhouse has a high pollutant load, which is characteristic of
slaughterhouses due to the large amount of organic waste, fats, suspended
solids, and nutrients present in their effluents (Bermúdez, 2019; Manjarres,
2023). The initial physicochemical assessment revealed an average pH of 8.61,
indicating a slightly alkaline environment, common in industrial wastewater due
to the presence of nitrogen compounds and the interaction of chemical and
biological processes (Rodríguez, 2021; Soto et al., 2020).
Electrical
conductivity was found to be high at 1393 µS/cm, reflecting a high
concentration of dissolved salts from cleaning products, blood residues, and
other organic and inorganic solutes (Quishpe et al., 2020; Landeta, 2019). High
levels of conductivity can affect water quality and its subsequent use, as well
as influencing toxicity to aquatic organisms (Muñoz, 2009; Manrique &
Piñeros, 2016).
Parameters
related to turbidity and color are important indicators of water quality and
reflect the amount of suspended solids and organic
matter in suspension. In this study, turbidity reached values of 470 NTU and
color was 15,700 Pt/Co units, indicating a considerable load of solids and
organic matter, which can cause clogging problems in receiving bodies and
affect aquatic photosynthesis processes (Biswas, 2021; Misal & Mohite,
2017). These high levels are consistent with previous reports on slaughterhouse
effluents, where the combination of blood, fat, and solid waste contributes to
opacity and dark coloration (Sánchez & Cueva, 2013; Bermúdez, 2019).
In terms of
nutrients, significant concentrations of nitrogen were detected in the form of
nitrites (2.9 mg/L) and nitrates (79 mg/L), as well as phosphates at 49 mg/L.
These concentrations exceed the recommended limits for effluent discharge,
implying a high risk of eutrophication in natural water bodies, promoting algal
proliferation and affecting biodiversity (Qiu et al., 2016; Manyuchi
et al., 2017). Nitrogen and phosphorus are essential nutrients, but in excess
they contribute to environmental degradation, a recurring problem in areas with
intensive industrial and agricultural activity (Rodríguez, 2021; Cabrera et
al., 2022).
Chemical
oxygen demand (COD) and five-day biochemical oxygen demand (BOD5) reached
values of 4980 mg/L and 2900 mg/L, respectively, indicating a very high organic
load. These demands reflect the amount of biodegradable and non-biodegradable
organic matter present in the effluent, key parameters for assessing pollution
and designing appropriate treatments (Pérez & Carrasco, 2019; Maza, 2017).
High BOD and COD values are typical in wastewater from the meat industry and
slaughterhouses, as a result of blood, fat, tissue, and animal remains (Bravo,
2019; Manjarres, 2023).
Total solids
(4524 mg/L) and dissolved solids (847.7 mg/L) are also high, confirming the
need for treatment to effectively reduce suspended particles and soluble
materials to avoid negative impacts on receiving water bodies (Rodríguez, 2021;
Manrique & Piñeros, 2016). The presence of solids contributes to increased
turbidity and can affect aquatic fauna, as well as hindering subsequent
treatment processes (Soto et al., 2020; Sánchez & Cueva, 2013).
Various
studies have shown that slaughterhouses are a major source of water pollution
in Ecuador and other regions due to the lack of adequate treatment systems and
improper waste management (Quishpe et al., 2020; GAD Ibarra, 2018). For
example, Landeta (2019) and Rodríguez (2021) highlight that the direct or
insufficiently treated discharge of wastewater into rivers and streams produces
negative environmental effects such as eutrophication, fish mortality, and
deterioration of drinking water quality. In addition, these effluents may
contain pathogenic microorganisms that pose a risk to public health (Soto et
al., 2020).
The problem
is exacerbated in rural and semi-urban areas, where technical and economic
constraints hinder the implementation of conventional treatment plants (Muñoz,
2009; Biswas, 2021). Therefore, the search for accessible, sustainable, and
low-cost technologies is a priority to mitigate the environmental impacts
associated with slaughterhouses (Misal & Mohite, 2017; Cabrera et al.,
2022).
In
conclusion, the physicochemical characterization carried out confirms the high
pollutant load of the wastewater from the Pelileo Municipal Slaughterhouse,
coinciding with the scientific literature and highlighting the urgent need to
implement efficient treatment systems, such as worm biofilters, which have
proven effective in reducing these critical parameters (Manjarres, 2023; Arora
& Saraswat, 2021).
Efficiency
of the worm biofilter in removing contaminants
After the
implementation of the biofilter with Eisenia foetida worms,
significant reductions were observed in all parameters analyzed. The pH of the
treated water decreased to 7.64, within the optimal range for most aquatic
organisms and in accordance with the limits established by Ecuadorian
environmental regulations (Manjarres, 2023). Electrical conductivity was
reduced to 887.2 µSiemens/cm, indicating a decrease in the concentration of
dissolved salts, possibly due to retention and microbial metabolism favored by
the biofilter (Biswas, 2021).
Color and
turbidity showed substantial improvement, with final values of 965 Pt/Co units
and 32 UTN, respectively, indicating effective treatment of organic matter and
suspended solids. This clarification is essential to avoid negative impacts on
receiving bodies and facilitate water reuse (Misal & Mohite, 2017).
With regard
to nutrients, nitrites decreased to 0.15 mg/L, nitrates to 45 mg/L, and
phosphates to 9.5 mg/L, representing a removal of 94.83%, 43.04%, and 80.61%,
respectively. This reduction helps mitigate eutrophication and problems
associated with excess nutrients in aquatic systems (Qiu et al., 2016; Manyuchi
et al., 2017).
Chemical and
biochemical oxygen demand showed very significant decreases, reaching values of
350 mg/L for COD and 178 mg/L for BOD5, equivalent to reductions of 92.98% and
93.86%. This confirms the high capacity of the biofilter to degrade
biodegradable organic matter, comparing favorably with other biological
technologies (Bravo, 2019; Cabrera et al., 2022).
Total and
dissolved solids, indicators of particulate pollution, were reduced to 6.25
mg/L and 560 mg/L, respectively, demonstrating the system's ability to retain
solid particles and prevent the generation of polluting sludge (Maza, 2017;
Pérez & Carrasco, 2019).
These
results are consistent with international studies that value vermifiltration as
an ecological, economical, and efficient solution. For example, Arora and
Saraswat (2021) documented similar reductions in BOD and COD, while Cabrera et
al. (2022) showed 86.9% efficiency for BOD5 in the treatment of wastewater from
the meat industry, demonstrating the versatility of the technology.
Operational
aspects, maintenance, and applicability
Hydraulic
retention time (HRT) is one of the most important parameters for the design and
operation of worm biofilters, as it directly influences the effectiveness of
the biological process. In this study, the estimated HRT was approximately 24
hours, which is considered adequate for Eisenia foetida worms to perform their
metabolic functions and for the associated microbial community to degrade the
organic matter present in the wastewater (Biswas, 2021; Bravo, 2019). The
literature indicates that too short an HRT can limit the necessary contact
between the water and the filter medium, reducing the removal of contaminants,
while excessive HRT can cause bed saturation and generate anaerobic conditions,
compromising the stability and efficiency of the system (Misal & Mohite,
2017; Pérez & Carrasco, 2019).
During
biofilter operation, a periodic maintenance regime was implemented to ensure
the proper functioning of the system. This maintenance included manual aeration
and mixing of the filter bed, activities aimed at preventing substrate
compaction and maintaining the permeability necessary for adequate wastewater
flow (Bermúdez, 2019; Liberio, 2019). These actions also allow for a sufficient
supply of oxygen, a critical factor in preventing the generation of unpleasant
odors and the proliferation of anaerobic microorganisms that can negatively
affect effluent quality (Soto et al., 2020; Manyuchi et al., 2017).
Constant
monitoring of environmental parameters, such as substrate moisture and
temperature, was key to the survival and optimal activity of the worms. Eisenia
foetida worms are sensitive to sudden changes in these conditions, so
maintaining a stable environment ensures the biological stability of the
biofilter and maximizes its performance (Manjarres, 2023; Liberio, 2019). The
adaptability of these worms to different environments has been widely
documented, and their role as a bioremediation agent positions them as a
fundamental component of sustainable treatment systems (Arora & Saraswat,
2021; Cabrera et al., 2022).
A notable
advantage of the biofilter was the absence of unpleasant odors and undesirable
solid waste during operation, which facilitates its application in urban and
rural contexts without the negative impacts typically associated with
conventional technologies, such as anaerobic systems or lagooning (Manjarres,
2023; Bermúdez, 2019). In addition, the process generates high-quality humus as
a by-product, an organic fertilizer that can be used in agricultural
activities, thus promoting a sustainable cycle and contributing to the local
circular economy (Coronel, 2015; Landeta, 2019).
In terms of
the quality of the treated water, analyses confirmed that it complied with the
maximum permissible limits defined in Ecuadorian environmental regulations
(TULSMA), demonstrating the technical and environmental viability of the
biofilter for wastewater treatment in slaughterhouses, especially in locations
where investment in conventional systems is limited or non-existent (GAD
Ibarra, 2018; Rodríguez, 2021). This regulatory compliance is essential to
ensure the protection of receiving water bodies and public health.
This study
contributes to the growing body of scientific evidence supporting the use of
vermicompost filters as an economical, ecological, and efficient alternative
for the treatment of industrial and municipal wastewater. The ease of operation
and low maintenance costs represent significant advantages over conventional
systems that require high energy consumption and complex sludge management
(Pérez & Carrasco, 2019; Manyuchi et al., 2017). In addition, the
biofilter's adaptability to different organic loads and types of water makes it
applicable in multiple industries, including agribusiness, fishing, and dairy
(Maza, 2017; Bravo, 2019).
We recommend
expanding the use of this technology in other rural and industrial areas, as
well as conducting complementary studies to optimize operating parameters, such
as irrigation rate, substrate composition, and hydraulic retention time, in
order to maximize process efficiency and facilitate the reuse of treated water
for irrigation or production processes, thereby contributing comprehensively to
environmental and economic sustainability (Biswas, 2021; Arora & Saraswat,
2021).
Conclusions
This
study has demonstrated that the implementation of a biofilter with Californian
red worms (Eisenia foetida) represents an effective,
sustainable, and viable alternative for the treatment of wastewater from the Pelileo Municipal Slaughterhouse. The high removal capacity
of critical pollutants, including organic matter, nutrients, and suspended
solids, confirms that this biological system is capable of significantly
reducing the pollutant load present in these highly polluting effluents,
achieving efficiencies greater than 90% in parameters such as biochemical
oxygen demand (BOD5) and chemical oxygen demand (COD). This positions the
biofilter as a technology comparable to, and in some cases superior to,
conventional treatment systems, but with considerable advantages in terms of
low operating costs, ease of maintenance, and lower environmental impact.
Initial
characterization of the wastewater showed severe contamination with high levels
of nutrients such as nitrates, nitrites, and phosphates, as well as high
concentrations of total and dissolved solids, which affect water quality and
pose a risk to public health and aquatic ecosystems. The effective reduction of
these parameters after passing through the biofilter confirms the system's
ability to mitigate the negative effects of these contaminants, preventing
eutrophication and other problems associated with the discharge of untreated
effluents. The operational stability of the system, evidenced by the
maintenance of favorable environmental conditions for the survival and activity
of the worms, was fundamental to ensuring the continuous efficiency of the
process.
In addition,
the biofilter stood out for its low energy requirements and the absence of
sludge or solid waste generation, which facilitates its operation in rural or
semi-urban areas where infrastructure and technical resources are limited. This
feature represents added value by reducing costs and risks associated with
sludge disposal, one of the main challenges in conventional systems. The
absence of unpleasant odors and the simultaneous production of high-quality
humus as a by-product add an additional dimension of sustainability, allowing
the organic waste generated to be used in agriculture and promoting the local
circular economy.
The
hydraulic retention time of approximately 24 hours was a determining factor in
the efficient degradation of organic matter, as it allowed adequate contact
between the wastewater and the active biological medium. Regular maintenance,
including manual aeration and prevention of filter bed compaction, was
essential to maintain the permeability of the system and the health of the
vermicomposting biomass. These aspects highlight the importance of careful
management and constant monitoring to maximize efficiency and avoid adverse
conditions, such as the emergence of anaerobic environments or mass worm
mortality.
Compliance
of the treated water parameters with Ecuadorian environmental regulations
(TULSMA) supports the applicability of the biofilter for discharge or reuse in
productive activities, which is essential for environmental protection and
water resource sustainability. The versatility of the system suggests its
possible extension to other industries that generate high organic loads, such
as agribusiness, the dairy industry, or fishing, increasing the positive impact
of this technology on integrated wastewater management.
The Eisenia
foetida worm biofilter combines technical efficiency, environmental
sustainability, and economic viability, making it an appropriate solution for
highly complex environmental problems in contexts with limited resources.
Future studies should focus on optimizing operating parameters such as
irrigation rate, substrate composition, and retention times to further enhance
efficiency and explore integration with complementary treatment systems or
water reuse in closed production cycles.
This
research contributes to scientific knowledge on clean technologies applied to
industrial wastewater treatment, especially in the Latin American context,
promoting the adoption of innovative solutions that respond to real sustainable
environmental management needs. The widespread implementation of
vermicomposting biofilters could represent a significant shift towards more
responsible production and environmental management models, with tangible
benefits for human health, the environment, and the local economy.
References
Arora, A., &
Saraswat, S. K. (2021). Vermifiltration technology
for wastewater treatment: A review. Environmental Technology &
Innovation, 21, 101275. https://doi.org/10.1016/j.eti.2020.101275
Bermúdez, R.
(2019). Estudio del sistema lombrifiltro para tratamiento de aguas
residuales en la industria láctea. Quito: Universidad Central del Ecuador.
Biswas, S. (2021).
Efficiency of vermifiltration in municipal
wastewater treatment and nutrient recovery. Journal of Environmental
Management, 280, 111754. https://doi.org/10.1016/j.jenvman.2020.111754
Bravo, J. (2019).
Economic feasibility of vermifiltration in food
industry wastewater treatment. Water Science and Technology, 79(2),
234-242. https://doi.org/10.2166/wst.2018.456
Cabrera, M.,
Sánchez, L., & Torres, J. (2022). Application of vermifiltration
in the treatment of wastewater from the meat processing industry. Journal
of Cleaner Production, 338, 130574.
https://doi.org/10.1016/j.jclepro.2022.130574
Coronel, J. (2015).
Caracterización biológica de Eisenia foetida para sistemas de
vermifiltración. Revista Ecuatoriana de Ciencias Ambientales, 12(1),
1-12.
GAD Ibarra. (2018). Diagnóstico ambiental de los centros de
faenamiento en la provincia de Imbabura.
Landeta, M. (2019). Tratamiento de aguas residuales en centros de
faenamiento: alternativas ecológicas. Riobamba: ESPOCH.
Liberio, J. (2019). Adaptación y alimentación de Eisenia foetida
en biofiltros. Revista Latinoamericana de Biotecnología Ambiental, 14(3),
30-41.
Manjarres, D. A. (2023). Evaluación de un biofiltro de lombrices
para la disminución de la carga orgánica en las aguas residuales del Camal
Municipal de Pelileo (Tesis de licenciatura). Escuela Superior Politécnica
de Chimborazo.
Manrique, A., & Piñeros, R. (2016). Evaluación comparativa de
sistemas naturales para tratamiento de aguas residuales. Ingeniería y
Ambiente, 9(1), 15-25.
Maza, A. (2017). Remoción de contaminantes en aguas residuales
pesqueras mediante lombrifiltro. Journal of Water Process Engineering, 20, 50-57.
https://doi.org/10.1016/j.jwpe.2017.05.004
Misal, S., &
Mohite, S. (2017). Vermifiltration: an effective
biological wastewater treatment technology. Environmental
Technology, 38(3), 365-374. https://doi.org/10.1080/09593330.2016.1205507
Muñoz, M. (2009). Tecnologías alternativas para el tratamiento de
aguas residuales. Revista Iberoamericana de Tecnología Ambiental, 14(1),
20-30.
Manyuchi, C., Chimbari, M. J., & Mukaratirwa, S. (2017). Vermifiltration for wastewater treatment and reuse
in irrigation. Environmental Science and Pollution Research, 24(5),
537-546. https://doi.org/10.1007/s11356-016-8120-4
Pérez, C., &
Carrasco, L. (2019). Tratamiento de aguas residuales lácteas mediante
sistemas lombrifiltro. Revista de Ingeniería Química, 28(2), 40-45.
Qiu, H., Yu, J., Yang, L., & Liu, Y. (2016). Enhancing constructed wetland performance by
Eisenia foetida earthworms. Ecological
Engineering, 91, 410-416. https://doi.org/10.1016/j.ecoleng.2016.02.027
Quishpe, G.,
Valdivieso, A., & Aguilar, L. (2020). Evaluación del impacto
ambiental en centros de faenamiento en Ecuador. Revista Latinoamericana de
Ciencias Ambientales, 25(2), 45-53.
Rodríguez, L. (2021). Impacto ambiental de las aguas residuales en
camales de Ecuador. Revista Científica de Ingeniería Ambiental, 17(1),
18-25.
Sánchez, P., & Cueva, J. (2013). Aplicación de humedales
artificiales para el tratamiento de aguas residuales. Ingeniería Ambiental,
7(1), 8-15.
Salazar, J. (2005). Alternativas económicas para el tratamiento de
aguas residuales en zonas rurales. Revista Iberoamericana de Tecnología
Ambiental, 10(1), 1-10.
Soto, F., Paredes, M., & Ramírez, M. (2020). Contaminación
orgánica en centros de faenamiento: diagnóstico y tratamiento. Revista de
Ingeniería Sanitaria, 35(1), 20-30.