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| Author(s): |
Tamires Lima da Silva
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Botucatu. 2019-09-10. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agronômicas. Botucatu |
| Defense date: | 2019-07-15 |
| Advisor: | Rodrigo Máximo Sánchez Román; João Gabriel Thomaz Queluz |
| Abstract | |
Rural communities and traditional populations present a lack of basic sanitation services, as collection and treatment of sewage. In small rural areas and settlements of traditional people is common the practice of agriculture, mostly for vegetable production. Domestic wastewater treatment (DWW) for agricultural reuse can promote environmental, social and economic improvements. Decentralized technologies for DWW of easy installation, operationality and low-cost are the most viable options for installation in rural areas and settlements of traditional people. The objective of this research was to evaluate the efficiency of a low-cost system of domestic wastewater treatment consisting of biological filter bed (BFB) and solar disinfection reactor (SODIS) for the purpose of agricultural reuse in rural communities and traditional populations. The pilot study was conducted at College of Agronomic Sciences- FCA, UNESP, Botucatu-SP, Brazil. Three biological filter bed (BFB's) installed in parallel were used. Each BFB presented an effective volume of 0.16 m3 and consisted of four rectangular fiberglass water boxes, connected in series, filled with gravel (size range 4.8 mm-9.5 mm) to a height of 30 cm. During the research period, the secondary effluent from Botucatu City Wastewater Treatment Plant (WWTP-Lageado) used as affluent for the BFB's, presents an average flow of 0.15 m3 d-1. The hydraulic detention time of the DWW in each BFB was approximately 1.06 days. The efficiency of the BFB's was evaluated by the analysis of the following parameters: biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total solids (TS), total dissolved solids (TDS), turbidity, pH, total nitrogen (N), phosphorus (P), potassium (K), electrical conductivity (EC), total coliforms, Escherichia coli (E. coli) and helminth eggs. The DWW treated by the BFB's was directed to three black coloured solar disinfection reactors (SODIS), that presented a concrete base and shape of an inverted truncated cone, where three fixed depths of DWW (10, 15 and 20 cm) were tested in order to verify which of them would be more efficient in inactivating fecal coliforms (E. coli). These three DWW depths were exposed to solar radiation for a period of 10 hours (from 08:00 a.m. to 6:00 p.m.) and the parameters of global solar radiation, temperature, pH, COD and E. coli were monitored. With the goal of evaluating the influence of the solar radiation variations along the year on the efficiency of the disinfection process, DWW samples were collected in two periods: from May to July 2018 (Autumn-winter period), and from December 2018 to March 2019 (Spring-summer period). The BFB's presented average removal efficiency of 50.9%, 86.2%, 95.8%, 41.6%, 97.8% for BOD, COD, TSS, TS and turbidity, respectively. The DWW treated by the BFB's and directed to the SODIS reactors after four hours of exposure to direct sunlight, in the two periods tested, presented quality in accordance with the World Health Organization (WHO) guideline for unrestricted irrigation (Fecal coliforms ≤ 1.000 MPN 100 mL-1). Comparing the fixed DWW depths of 10, 15 and 20 cm by the analysis of variance-ANOVA, with the response variable the ratio (N/No), in which (No) represents the initial population of E. coli and (N) represents the remnant population of E. coli after exposure to solar radiation. The ANOVA results showed that there were no differences statistically significant between the DWW depth tested. Mathematical models representing the remaining fraction of fecal coliforms in the DWW (N/No), in relation to the global solar radiation dose accumulated on the SODIS reactors were developed. The concentrations of N, P and K in the DWW showed that it has a nutritional potential for vegetable production of 536.1 kg ha-1 year-1 of nitrogen; 157.68 kg ha-1 year-1 of phosphorus and 504.5 kg ha-1 year-1 of potassium. The combination of the treatment methods: BFB and SODIS is a sustainable low-cost and maintenance solution that can promote the safe use of domestic wastewater for irrigation of farmlands in rural communities and traditional populations. (AU) | |
| FAPESP's process: | 17/14729-3 - Efficiency analysis of a low cost treatment system of wastewater for agricultural reuse purposes in rural communities and traditional populations |
| Grantee: | Tamires Lima da Silva |
| Support Opportunities: | Scholarships in Brazil - Master |