RESUMEN
Exploring alternative fertilizers is crucial in agriculture due to the cost and environmental impact of inorganic options. This study investigated the potential of sewage-derived biofertilizers on the growth and physiology of Amaranthus cruentus plants. Various treatments were compared, including control treatments with inorganic fertilizer and treatments with biofertilizers composed of microalgae, biosolids and reclaimed water. The following traits were investigated: photosynthetic pigments, gas exchange, growth, and leaf nutrient concentrations. The results showed that the concentrations of N, P, Cu, Fe Zn and Na nutrients, in the dry microalgae and biosolids, were quite high for the needs of the plants. The wet microalgae presented high concentration of Cu, Fe and Zn nutrients while reclaimed water contained high concentration of N, K, Ca and S. Na and Zn nutrients increased in the leaf of plants treated with dry microalgae and biosolid, respectively. At the beginning of the flowering phase, total chlorophyll and carotenoids contents were lower for plants grown with wet microalgae while for plants grown with higher doses of biosolid or reclaimed water total chlorophyll was increased, and carotenoids were not affected. Lower photosynthetic pigments under wet microalgae resulted in lower photosynthetic rates. On the other hand, amendments with dry microalgae and biosolid increased photosynthetic rates with the biosolid being the most effective. Higher applications of biosolid, wet and dry microalgae produced a considerable increase in shoot biomass of amaranth, with the dry microalgae being the most effective. Additionally, reclaimed water obtained after tertiary treatment of sewage with microalgae and biosolids applied alone showed promising effects on plant growth. Overall, these findings suggest that organic fertilizers derived from sewage treatment have the potential to enhance plant growth and contribute to sustainable agricultural practices.
Asunto(s)
Amaranthus , Purificación del Agua , Aguas del Alcantarillado , Biosólidos , Fertilizantes , Plantas , Minerales , Nutrientes , Agua , Carotenoides , ClorofilaRESUMEN
A DEWATS (decentralized wastewater treatment system) is an alternative for expanding sanitation. In Brazil, DEWATS is acknowledged by law and is part of the National Sanitation Plan strategy for achieving the treatment of 85.6% of all the generated wastewater by 2033, improving the current treatment index of 49%. This review's aim is to identify DEWATS studies in Brazil and to verify their potential for narrowing the national wastewater treatment deficit. Hence, aspects such as cost, maintenance, and efficiency were assessed. The archival research method (ARM) was used to identify papers published in the last 20 years through the scientific databases of Scopus, Science Direct, and Web of Science. Data regarding the general characteristics of each study were collected and compared to Brazilian environmental regulation and sanitation status. The results showed the evaluation of different technologies such as DEWATS, highlighting their flexibility and potential use in 79% of Brazilian counties. However, although 81% of the studies conducted performance analysis, none covered the main parameters required by Brazilian law. Although legal gaps for DEWATS improvement and consolidation have been identified and the interest in studying DEWATS has been increasing in the last five years, many barriers to their widespread use remain.
Asunto(s)
Aguas Residuales , Purificación del Agua , Brasil , Investigación/tendenciasRESUMEN
The scarcity of natural resources supports the perspective of reusing treated effluents, mainly in agriculture, where the reduction in the demand of drinking water and the provision of alternative sources for nutrients are important. However, the process of disinfection, essential to the protection of human health, generates deleterious by-products to both humans and the environment. This research aimed to evaluate the use of ozone as a disinfectant for wastewater treated by anaerobic/aerobic baffled reactor for later agricultural reuse. Disinfection tests were conducted by applying ozone, in batch, with applied dosages of 5, 8, and 10 mg O3 /L and contact time of 7 min. All the tests led to formaldehyde formation, therefore within the standard suggested by the World Health Organization. For the indicators total coliforms and Escherichia coli, the ozone was considered effective, satisfying the criteria for agricultural reuse according to the World Health Organization of a dosage of 8 mg O3 /L. PRACTITIONER POINTS: Proposal of decentralized system (anaerobic/aerobic baffled reactor + ozone disinfection) for effluent treatment for agricultural reuse. Formation of formaldehyde dependent on applied ozone dose. Demand of ozone consumed preferentially for the formation of by-products, with low removal of COD. High formaldehyde formation (high ozone demand) can impair the inactivation of pathogens. System promotes effluent that meets the standards established by the World Health Organization (WHO) for agricultural reuse.
Asunto(s)
Ozono , Purificación del Agua , Anaerobiosis , Desinfección , Formaldehído , Humanos , Microbiología del AguaRESUMEN
Decentralized sanitary wastewater treatment has become a viable and sustainable alternative, especially for developing countries and small communities. Besides, effluents may present variations in chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total nitrogen values. This study describes the feasibility of using a pilot upflow anaerobic sludge blanket (UASB) reactor to treat wastewater with different organic loads (COD), using black water (BW) and sanitary wastewater, in addition to its potential for preserving nutrients for later recovery and/or reuse. The UASB reactor was operated continuously for 95 weeks, with a hydraulic retention time of 3 days. In Phase 1, the reactor treated simulated BW and achieved 77% CODtotal removal. In Phase 2, treating only sanitary wastewater, the CODtotal removal efficiency was 60%. Phase 3 treated simulated BW again, and CODtotal removal efficiency was somewhat higher than in Phase 1, reaching 81%. In Phase 3, the removal of pathogens was also evaluated: the efficiency was 1.96 log for Escherichia coli and 2.13 log for total coliforms. The UASB reactor was able to withstand large variations in the organic loading rate (0.09-1.49 kg COD m-3 d-1), in continuous operation mode, maintaining a stable organic matter removal.
Asunto(s)
Aguas del Alcantarillado , Purificación del Agua , Anaerobiosis , Reactores Biológicos , Proyectos Piloto , Eliminación de Residuos LíquidosRESUMEN
Reuse of wastewater is a practice that has been employed all over the world, mainly in agriculture, where the main aim is to reduce the demand for water and provide nutrients. However, these waters for reuse often have excessive amounts of pathogenic microorganisms, requiring a specific disinfection step even after being subjected to a purification process. Thus, this research aimed to evaluate the potential use of calcium hypochlorite and sodium hypochlorite as disinfectant agents for the sanitary effluent of the treatment system based on constructed wetlands for later reuse. Disinfection tests were carried out in batch, using three dosages of hypochlorite (5, 10 and 15 mg.L-1) and different contact. In all disinfection tests, inactivation of indicator microorganisms (total coliforms and E. coli) was considered effective for the two disinfectant agents adopted, satisfying the criteria for reuse according to the World Health Organization (WHO). There was no formation of trihalomethanes after disinfection tests.