REDUCING THE ENVIRONMENTAL IMPACT OF UNHAIRING PROCESS IN COLOMBIA TANNERIES
REÚSO DE LOS BAÑOS RESIDUALES DEL PROCESO DE PELAMBRE SIN AFECTAR LA CALIDAD DEL PROCESO
Diana Marcela Fúquene 1
Jorge Orlando Manrique 2
Leonardo Emilio Calle 3
Andrea Viviana Yate 4
1 Magíster en ingeniería ambiental, candidato a Doctor en proyectos, Universidad Nacional Abierta y a Distancia – UNAD, Grupo de investigación en Estudios Ambientales Aplicados – GEAA, Bogotá – Colombia. geaa.unad@gmail.com
2 Especialista en ingeniería ambiental, Universidad Nacional de Colombia, Bogotá – Colombia. jomanriquep@unal.edu.co
3 Magíster en ingeniería ambiental, Universidad Nacional de Colombia, Bogotá – Colombia. leonardocallep@yahoo.com
4 Magíster en ingeniería química, Universidad Nacional Abierta y a Distancia – UNAD, Grupo de investigación en Estudios Ambientales Aplicados – GEAA, Bogotá – Colombia. geaa.unad@gmail.com
Abstract: In Colombia, the largest percentage of tanneries is located in Cundinamarca, exactly in the municipality of Villapinzón, which is the focus of study, because it uses the upper basin of the Bogotá River as a source of discharges wastewater. The tanneries are one of the productive sectors that have the greatest negative impact on the water resource, specifically, the unhairing process that uses 1:1 mass ratio (skin-water). Based on this, this project carries out an evaluation on the impact of reusing the residual liquors generated in the unhairing process without altering the quality of the final product, by carrying out tests at pilot plant level of the process of unhairing without sulfur and unhairing mixed to salted hides. The discharges generated by the unhairing process without sulfur are recirculated directly, while the unhairing mixed discharges has a preview treatment of oxidation, coagulation and sedimentation, both discharges are monitored by measuring four physical-chemical parameters of sanitary interest. The obtained results allow to establish that, the recirculation of the waters on unhairing process does not increase the costs, on the contrary, it presents a saving and diminishes the negative environmental impact generated in the upper basin of the Bogotá River, taking into account that the approximate volume of reuse of water is 50%, confirming the hypothesis raised on the recirculation of effluents from this process.
Keywords:Minimize, reduction environmental impact, reuse dumping of hide, leather Quality, unhairing process, tannery.
Resumen: En Colombia, el mayor porcentaje de empresas curtidoras se ubican en Cundinamarca específicamente en el municipio de Villapinzón, que es el foco de estudio, debido a que utiliza la cuenca alta del río Bogotá como fuente receptora de los vertimientos que genera. Las curtiembres son uno de los sectores productivos que mayor impacto negativo tienen sobre el recurso hídrico, específicamente, la etapa de pelambre que emplea una relación másica 1:1 (piel – agua). En función de esto, este proyecto realiza una evaluación sobre el impacto de reutilizar los licores residuales generados en el proceso de pelambre sin alterar la calidad del producto final, mediante la realización de ensayos a nivel de planta piloto del proceso de pelambre sin sulfuro y pelambre mixto a cueros vacunos salados. Los vertimientos generados por el proceso con pelambre sin sulfuro son recirculados directamente, mientras que a los vertimientos del pelambre mixto se les realiza un tratamiento de oxidación, coagulación y sedimentación, ambos vertimientos son monitoreados mediante la medición de cuatro parámetros físico-químicos de interés sanitario. Los resultados obtenidos permiten establecer que, la recirculación de las aguas de pelambre no incrementa los costos, por el contrario, presenta un ahorro y disminuye el impacto ambiental negativo generado en la cuenca alta del río Bogotá, teniendo en cuenta que el volumen aproximado de reutilización del agua es del 50%, confirmando la hipótesis planteada sobre la recirculación de los efluentes de este proceso.
Palabras Clave: Minimización del impacto ambiental, Reutilización de vertimientos de pelambre, Calidad del cuero.
Graphic summary:
INTRODUCION:
Tanning is a process to transform animal skins to leather through a sequence process that include chemical and mechanical steps in order to obtain a product resistant to microbial degradation, heat and moisture stress (Alibardi & Cossu, 2016). Worldwide, tannery industry presents high environmental impacts, associated to air and water pollution problems, causing emissions with high biological oxygen demand, chemical oxygen demand and total suspended solids. (Alibardi & Cossu, 2016; Sivagami, Sakthivel, & Nambi, 2017; Martínez & Romero, 2018). In this way, it´s neccesary to propose alternatives to reduce the polluting load, as include a unhairing mixte or ecological, wich let the reduction of sodium sulphide quantities commonly used in the chemical formulation.
Europe has high production of leather and maintain strict controls for the preservation of the environment through clean and efficient production programs. In contrast, latin america has to spend large amounts of money to repair the damages caused by tanneries (Martínez & Romero, 2018; Dettmer, Cavalli, Ayub, & Gutterres, 2013). In Colombia, around the 80% of the total tanneries industries are located in Bogotá and Cundinamarca, being Villapinzón one of the leading producers of leather nationwide (export type, webs and tulas). However, due the proximity to the Bogotá river watershed, it is used as a source and dumping of liquor waste without any previous treatment (Numpaque & Viteri, 2016). In the leather industry, the major consumption of water occurs during the unhairing process with at least a mass ratio of 1:1. The Villapinzón tanneries frequently use two types of unhairing methods given by a chemical supply; a mixture that contain chemical and enzymatic compounds with Sulphur, and a mixture without Sulphur.
Although some tanneries in Villapinzón in order to reduce the negative impact on the river, reuse the wastewater on tanning process for about 16 months, tanneries that produce exportation type leather, disagrees with this technique, arguming that this practicum damage the leather’s quality (Fuquene, 2011). The aim of this study was to evaluate the discharges generated by each unhairing method in order to establish a methodology for assessing the effect of the reuse of these effluents on the tanning process and the possibility of dumping effluents in the Bogota river.
Carrillo Neira & Muñoz Labrador (2014) stated that unhairing liquor could be reused twice for the next unhairing processes with or without depleted. When unhairing liquor is used twice, it has been determined that water consumption decrease by 32%, sodium sulfur by 5% and lime by 56,1%, with a cost benefit ratio upper one. In another study carried out by Gomez Bustamante & Echeverry Giraldo (2010) determine after ten or more reuses of unhairing wastewater, the characteristics of the liquor at the laboratory level are stabilized.
MATERIALS AND METHODS
Materials
Tests were conducted using salted cattle hides sampled randomly from a local tannery. A mini drum (cylindrical rotating reactor, used for hide and leather processing) was used. Two different unhairing agents were used (sulphur formulation1, and sulphur free formulation2), both were recommended by chemical supplier house of Villapinzón3. All chemicals used for the physico-chemical treatment proposed of wastewater were analytical grade.
1Formulation: 0,5% anti winkle, 6% CaO, 2,2% Na2S, 100% H2O y 0,15% NaOH
2Formulation: 0,25% Koramin EKO, 1,8% Depilamin GS, 3,8% CaO y 100% H2O
3PROCUR S.A.
Method
Preparation of the unhairing hide:
For the scaling up, a hide was divided into four equal pieces as show in Fig. 1, in order to compare the effect of water recirculation in the unhairing hide evaluatedtre. Piece 1-A was washed and soaked with raw water, the wastewater obtained was used to wash and soak piece 2-A, section 3-A was treated with water discharge from 2-A, and section 4-A was performed with water discharge from the 3-A process. This procedure was conducted with both chemical formulations. Due to the water lost in each procedure, it was necessary to top up the volume required (according to the formulations) with raw water.
Fig 1. Bovine hide splitting for scale up test.
Unhairing test
Salted hides were thoroughly washed to remove salt, blood residues, debris, soil and manure. After that, the hide went through a process of soaking that aims to restore the hides moisture loss by addition of chemicals such as surfactants (Andrioli, Petry, & Guterres, 2015). At the end of this process, the hides were washed again and drip dried until they reached between 1.0 and 2.0 Degrees Baume (°Be).
Wastewater was collected at the end of each unhairing tests and evaluated by analyzing biological oxygen demand (DBO), chemical oxygen demand (DQO), chlorides and total suspended solid (TSS). Characteristics of the unhairing hide (output of hide and finished product) were evaluated according to method based of Sectorial Chamber of Leather – ANDI (2010)
Wastewater treatment
According with the recommendations of the chemical supplier house of Villapinzon, water discharge using sulphur free formulation does not require any additional treatment, just removal of the hair one hour prior to the end of dosing.
However, for wastewater obtained from treated mixed formulation with Sulphur, it was necessary to use a screening step (Agudelo, 2007), followed by a sulfide oxidation and coagulation–sedimentation step; in order to remove contaminants, present in water by the addition of chemical products, and removal of non-useful components from the hide, such as hair, fat and meat. The proposed treatment design was based on the Romero engineer's literature (Romero, 2010)
RESULTS AND DISCUSSION
Sulphur free formulation:
According with the flow balance shown in Fig. 2, salty hide requires 100% by weight water in the unhairing process, 43% of this is absorbed by the hide, 54% is left as industrial wastewater or effluent, which needs treatment and can be recirculated, and the remaining 3% is water combined with hair.
Fig 2. Water flow balance
Regarding the unhairing process using Sulfur free formulation, hide sections 2-A and 3-A present similar hair removal from the unhairing process without water recirculation. However, hair from section 4-A remained intact, indicating that unhairing process did not work after three water recirculation.
Fig. 3 presents four quality parameter measured to each water discharge, and its comparison with the standard required for waste water generated on tanneries. The obtained results indicate that the recommendation by the home provider of chemical inputs respect the formulation without Sulphur only applies to one water discharge recirculation, since the second recirculation is affected negatively on unhairing process, leaving hair on the hide. According to Fig 3 physicochemical analysis present an increment up to 64% from the first water discharge recirculation to the second one.
Fig 3. Effect of four quality parameter in the wastewater recirculation of Sulphur free formulation
Sulphur mixed formulation
Fig. 4 shows the flow balance of Sulphur mixed formulation. The water discharge is 56% of the inlet water, however, though the removing hair and sludge step the water discharge is reduced to 43%, being the total water to recirculate.
Fig 4. Water flow balance
According with Fig 5, this formulation shows low level in all physicochemical parameters measured regarding unhairing process Sulphur free formulation.
Additionally, unhairing process using mixed Sulphur formulation had good results in the hide aspect for the formulation with raw water and the first water recirculation. In both cases, the hide was without hair or hide debris, with homogeneous color, good size and open lines.
Fig 5. Effect of four quality parameter in the wastewater recirculation of Sulphur free formulation of sulphur mixed formulation
Using this formulation, it was observed that as the number of recirculation is increased, hairless skin clean without traces of skin looked, which improved the quality of the skin appalled. The first recirculation showed a high quantity of hair removal, leaving a remanence of 2%, while the second recirculation, 1% of the hair remained, and on the third water discharge recirculation the hide was completely free of hair.
Fig. 6 shows the effect of treatment (screening step, followed by a sulfide oxidation and coagulation–sedimentation step) on water discharge carried after the unhairing process.
Fig 6. Effect of four quality parameter of the wastewater treated
Importantly, on the third recirculation, the proposed wastewater treatment is adversely affected, which could be caused by the remnants of contaminants in the water from previous recirculation, which is due to the requiring of various dosages of reagents for treating water.
CONCLUSIONS
The recirculation of waste water from the unhairing process with a previous physico-chemical treatment is successful, considering that the unhairing process is performed by tanneries once a week on average.
Is not recommended to store untreated water due to it containing a high load of organic matter, which begins to decompose, generating problems of odors and gases which are harmful to health and the environment. In addition, water decomposition precludes its reuse in the unhairing process because the nature of the contaminants is unknown and when the hide absorbs the amount required for hydration, will adversely affect the quality characteristics of the final leather.
This study evaluated a maximum of three recirculation using a mixed Sulphur formula for the unhairing process. However, it is recommended that more experiments are performed in order to determine the maximum quantity of recirculations that would not affect the final product. Moreover, to identify the maximum recirculations before the water is saturated, and the physical-chemical treatment wont effective.
The wastewater recirculation from unhairing process does not increase costs to the operation process, instead, it represents a savings and reduces the negative environmental impact generated by each dumping of wastewater to the Bogota River. Moreover, water reuse promises to reduction the use of clean water by approximately 50%.
REFERENCES
