REGISTRO DOI: 10.5281/zenodo.12710102
Milena Penteado Chaguri1*
Milena Alves de Souza1
Rose Meire Vidotti2
RESUMO
O objetivo deste estudo foi avaliar a eficiência da macrófita aquática Eichhornia crassipes e escamas de tilápia no tratamento de efluente de curtume de pele de tilápia com diferentes tempos de retenção hidráulica. A eficiência do sistema em relação a redução do fósforo total foi de 44,3% e 62,95% na presença escamas e aguapé (EA), e de apenas aguapé (AG), respectivamente. A Remoção de DQO foi semelhante para ambos os tratamentos, respectivamente, 67,75% e 59,31% para a AG e AE. Quanto ao nitrogênio total, os valores foram significativamente diferentes para os diferentes tempos de retenção hidráulica (TRH), onde no dia 8 de eficiência caiu para 48,56%. O uso de macrófitas aquáticas e escamas podem ser considerados como uma alternativa de baixo custo para o tratamento de efluentes de curtumes de peles de tilápia. Ambos os tratamentos foram igualmente eficazes para remover os nutrientes do efluente, não diferindo significativamente.
Palavras–chave: macrófita, biofiltro, poluição aquática
ABSTRACT
The objective of the study was to evaluate the efficiency of the water macrophyte Eichhornia crassipes and tilapia scales to treat the effluent of a tannery that processes the skin of tilapia with different hydraulic retention times. The system efficiency with respect to total phosphorus reduction was 44.3% and 62.95% in the presence scales and water hyacinth (EA) and of water hyacinth only (AG), respectively. The DQO removal was similar for both treatments, respectively, 67.75% and 59.31% for AG and EA. As for total nitrogen, values were significantly different for the different hydraulic retention times (TRH), where on the 8th day efficiency dropped to 48.56%. The use of water macrophytes and scales may be considered as a low cost alternative to treat the effluents of tanneries that treat tilapia skin. Both treatments were equally effective to remove nutrients from the effluent, and did not differ significantly.
Keywords: macrophyte, biofilter, water poluition
INTRODUTION
Industrial effluents are the main cause of water pollution. These effluents contain all several toxic substances that affect adversely every live species, thus making it necessary to find effective ways of treating these effluents.
The leather industry is a polluter that may potentially cause serious environmental damage. The treatment of tannery effluents is complex and expensive, and most of the times is not feasible for small and medium size plants (Braile & Cavalcanti, 1993).
The scale consists of of a organic and inorganic fraction made up mainly by collagen hydroxyapatite, respectively. Aizawa et al. (1999) reported that hydroxyapatite due to high adsorption power may be used in the field of biomaterial to catalyze harmful ions; however, Villanueva et al. (2001) reports that collagen, which is made up of protein, presents certain properties that may explain the high adsorption power of this biomaterial.
The use of water plants may be a good alternative to treat effluents that contain small amounts of nutrients and organic matter. According to Zacarkim et al. (2007) some research has been conducted using wetlands to treat tannery effluents as a viable, low cost alternative.
The wetland system may be used to treat household and industrial pollution to effectively decrease the nutrients and heavy metal concentration, as well organic matter present in the effluents. The use of wetlands to treat effluents is more advantageous compared to conventional treatments, due to low cost easier management, no chemical products are necessary and later on the water plants can be used for other purposes (Salatti, 2003).
Eichhornia crassipes (water hyacinth) is a fast growing aquatic macrophyte that adapts easily and is capable of intensive nutrient assimilation, and therefore, a promising species to treat effluents. This plant can remove significantly large amounts of nitrogen, phosphorus and potassium from the water.
The development of bacteria activity and aquatic microorganisms in the rhizosphere are able to remove pathogens, organic matter and nutrients from de effluent (Ballem et al. 2007).
The objective of this paper was to evaluate the efficiency of two pilot plants used to treat effluents from a tannery that processes tilapia skin. The first treatment used the aquatic macrophyte Eichhornia crassipes and tilapia scales, while the second used only E. crassipes at different retention times.
MATERIAL AND METHODS
The work was conducted at the Aguape tannery, located in Pindorama, SP. The analysis were carried out at Centro de Aquicultura, UNESP, Jaboticabal, SP.
The effluent, which originated from the production line of tilapia leather, was treated by a system of biofilters, collected and transferred to a 500-l container. The effluent was then diluted in water, at 1:1 ratio, following the methodology described by Zacarkim et al. (2007).
The aquatic macrophyte Eichhornia crassipes was collected at CAUNESP, transported and conditioned for a week at the factory where the experiment took place. Two treatments were conducted to treat the residues.
The first consisted of different sized boxes disposed in series, where the first was a 500-l collector box, followed by a supplying 40-l container, a smaller box with 4 kg of fish scales and two 180-l boxes containing the water hyacinth as shown in Figure 1.
The second system used to treat the effluent consisted of a 500-l collecting tank, a 40-l supply box and three boxes containing the aquatic macrophytes all disposed in series as shown in Figure 2. Both systems were run at different hydraulic retention times (HRT) of 4, 6 and 8 days, a dynamic system with daily flow rate of 60 liters.
The macrophyte biomass represented about 80% of the box surface. The effluent used originated from the processing of 8 kg of tilapia skin.
The effluent was diluted in the collecting tank at 1:1 ratio (effluent: water) and dripped onto the supply box and subsequently to the others. To evaluate the water quality, effluent samples were collected at the inlet and outlet of each biofilter and frozen.
The samples were then taken to CAUNESP, where they were analyzed. Chemical oxygen demand (COD) was determined by the HACH Colorimetric method (model HACH DR890). Samples pH was determined at inlet and outlet of each filter using a pH meter Digimed, model DM-2.
Inflow and outflow samples were collected at the biofilters and taken to the laboratory to determine total nitrogen (TN), total ammonia nitrogen (N-NH3) and total phosphorus (TP). Total suspended solids were determined by filtering the samples using a fiberglass membrane with a diameter of 47 0.5 mm and 0.6-0.7 μm porosity (APHA, 1995).
Treatment efficiencies were evaluated using a 2×3 factorial design, the first factor laid out the two treatments (scales and water hyacinth x water hyacinth), the second factor laid out three retention times (4, 6 and 8 days) and three repetitions.
RESULTS AND DISCUSSION
Table 1 presents F values and the mean values of the studied variables. Total phosphorus reduction was 44.3% and 62.95%, for the scales and water hyacinth and water hyacinth only, respectively. According to Sipauba-Tavares (2000), this reduction is due to the fact that water hyacinth needs phosphorus to grow, and it is able to reduce the discharge of the nutrient in the system. Phosphorus is among the main substances present in the effluents and is associated with eutrophication of water, and proposed treatments reduce the impact on the environment. However, from the moment the saturation point is reached, the macrophyte is not able to absorb this nutrient any longer.
Chemical oxygen demand (COD) was similar for both treatments, 67.75% and 59.31% for water hyacinth only and water hyacinth and scales, respectively. Zacarkim et al. (2007) reported COD decrease of 73.41%, 79.91% and 63.46% at hydraulic retention times of 4, 6 and 8 days, respectively, for a tannery effluent treatment using Eichhornia crassipes. In the present study, there were no significant differences for HRT among treatments.
Total nitrogen differed significantly for the hydraulic retention times studied, where on the 8th day efficiency dropped to 48.56%, compared to values of 76.53% and 70.49% on the 4th and 6th day, respectively. According to Reidel et al. (2005), hydraulic retention time influences the efficiency of nutrient removal from the effluents.
Total ammonia nitrogen was reduced 85.79% in water hyacinth only treatment and 52.91% in water hyacinth plus scales treatment, but did not differ statiscally (Table 1). Also, total ammonia nitrogen values at different HRT were not significantly different.
Sipauba Tavares & Boyd (2005) did not report drop in the total ammonia nitrogen, total nitrogen, total phosphorus while treating Aquaculture effluents. However, in this study while using the same macrophyte to treat the effluent of a tilapia skin tannery it was observed a concentration drop of these nutrients.
From the results reported it can be seen that while water hyacinth is effective to treat the effluent, the presence of fish scales did not affect the results. However, the use of scales may help in the removal of other contaminants such as minerals and heavy metals, which a highly harmful to human beings and the environment as well. Sipauba Tavares & Boyd (2005) used aquatic macrophytes to treat Aquaculture effluents and reported a drop in total suspended solids. Hydraulic retention times affected significantly only total ammonia concentration, with the best results reported for 4 and 6 days.
CONCLUSIONS
The two studied treatments were not significantly different, but both removed efficiently nutrients present in the effluent of the tannery. The fish scale may be used as supporting element in the effluent treatment with water hyacinth. The pilot plant scale results have shown that water hyacinth and fish 130 scales might be a good alternative to treat the effluents of a tannery that process tilapia skin.
REFERENCES
Aizawa, M., Terado, T., Howell, F.S., Itatani, K. Preparation of spherical apatite particles by the homogeneous precipitation method in the presence of magnesium ions and their ion-exchange properties. Materials Research Bulletin, v.34, n. 8, p.1215–1225,1999.
APHA. American Public Health Association. 1995. Standard methods for examination water and wastewater. ed.: Arnold and Greenberg, Washington.
Ballem, A., Aita, C., Giacomini, S.J., et al. Eficiência do sistema lagoa de aguapés na remoção complementar de DQO e N de dejetos líquidos de suínos pré-tratados em reator aeróbico de biogrânulos. In: Congresso Brasileiro de Ciência do Solo, 31, 2007. Gramado- RS.
Braile, P.M.; Cavalcanti, J.E.W.A. 1993. Manual de tratamento de águas residuárias industriais. CETESB, São Paulo.
Reidel, A.; Damasceno, S.; Zenatti, D.C. et al. Utilização de efluente de frigorífico, tratado com macrófita auática, no cultivo de tilápia do Nilo. Revista Brasileira de Engenharia Agrícola e Ambiental, suplemento, p.181-185, 2005.
SALATTI, E. Utilização de sistemas wetlands construídas para tratamento de águas. Biológico, v. 6, n.½, p. 113-116, 2003.
SIPAÚBA TAVARES, L.H. Utilização de biofiltros em sistemas de cultivos de peixes. Informe Agropecuário, v. 21, n. 203, p. 38-43, 2000.
SIPAÚBA TAVARES, L.H., BOYD, C.E. Macrophyte biofilter for treating effluent from aquaculture In: Twenty-Second Annual Technical Report. Aquaculture CRSP, Oregon State University, Corvallis,
Oregon, p. 195-199, 2005.
Villanueva-Espinosa,J.F.,Hernández-Esparza,M., Ruiz-Trevino, F.A. Adsotive properties of fish scales of Oreochromis niloticus (Mojarra Tilápia) for metallic ion removal from waste water. Industrial & Engineering Chemistry Research, v. 40, n. 16, p. 3563-3569, 2001.
ZACARKIM, C.E.; GOMES, S.D.; PALACIO, S.M.; WELTER, R.A. Avaliação de sistema wetland construído no pós-tratamento de efluentes de curtume. In: Congresso brasileiro de engenharia sanitária e ambiental, 24, 2007.
TABLE
Table 1. F values and means obtained for total phosphorus (P), chemical oxygen demand (COD), total
Means followed by the same letters in the columns did not differ significantly by Tukey test, at 5% probability.
FIGURE
Figure 1. Layout of the pilot plant proposed to treat effluents using scales of tilapias and aquatic macrophytes (Eichhornia crassipes)
Figure 2. Layout of the pilot plant proposed to treat effluents using only aquatic macrophytes (Eichhornia crassipes).
1 Centro de Aquicultura- Unesp, Brazil
2 Instituto de Pesca, Brazil
*Corresponding author. e-mail address: mpchaguri@gmail.com