Antonio Claudio Testa Varallo

Alterations in attributes of a Red-yellow Latosol irrigated with reuse water

The reuse of treated sewage effluent to water bodies to supply water for irrigation has been of great advantage to agriculture, and the use if not regimented could bring changes in physical and chemical properties of soil. This paper aimed the evaluation of the physical and chemical properties alteration of a Red-yellow Latosol after the application of reuse water from an effluent treatment station of wetlands. The experiment was accomplished in laboratory using a soil column. First, 15 L of distilled water were applied in the soil column and after 15 L of reuse water and at interval of 5 L of water a sample was collected for analysis. The results showed decrease of nitrate, potassium and saturated hydraulic conductivity values and an increase in sodium, iron, manganese, zinc and electrical conductivity of the soil after water application. In this way, it may be concluded that the use of waste water for agronomic activities must be used in a rational way, mainly checking the elevation of sodium.

Use of treated wastewater for lettuce cultivation

Abstract. The purpose of reusing water on agriculture is saving good quality water to noble uses and using treated wastewater for irrigation, enabling economic gain and sustainability in agriculture. The objective of this study was to analyze the changes on chemical and microbiological characteristics of a Red Latosol dystrophic soil after the cultivation of lettuce irrigated with treated wastewater. The experiment was conducted in a greenhouse at the Center of Agricultural Science of UFSCar, in Araras/SP/Brazil. Lettuce seedlings were irrigated by drip using treated wastewater and potable water with 4 replications for each one. After the maturation, the plants were collected along with soil samples. The physical and chemical properties and heterotrophic microorganism and coliforms were analyzed. The parameters sodium adsorption ratio (SAR), BOD, magnesium, calcium, sodium, potassium, nitrate, chlorine, turbidity, pH, electrical conductivity (EC) and coliforms were analyzed on the irrigation water. The values of exchangeable sodium percentage and SAR on the plots irrigated with treated wastewater indicated soil salinization. The EC kept the value according to the standard for irrigation water in both treatments. It was observed an increase on soil of some nutrients (K, Ca, H, Al, S) after the cultivation. It was not observed presence of Escherichia coli on lettuce leaves and soil. The total coliforms at lettuces presented a risk of contamination for human health due the possible contamination. The treated wastewater did not cause damages on physical properties of soil and promoted increase of nutrients on soil.

Evaluation of sanity quality of letucce (Lactuca sativa, L.) irrigated with reuse water in comparison with traded samples

The misuse of hydric resources contributes to their scarcity, becoming interesting research about their reutilization. This work aimed to the evaluation of sanitary quality of lettuce irrigated with reuse water in comparison with samples traded in Taubate (SP). An experiment was developed in a greenhouse with 3 beds of lettuce irrigated with reuse water and 3 beds of lettuce irrigated with urban water of provisioning. After lettuce biological cycle had been completed, lettuce samples were collected from the beds (irrigated and non-irrigated with reuse water) and from the trade, and after that they were conducted to a laboratory. The analyses were realized using the multiples tubes methodology. The results showed that the samples from lettuce irrigated with urban water provisioning were not contaminated with total and thermotolerants coliforms, while the ones irrigated with reuse water were contaminated by total coliforms. The samples from commercialized lettuce were contaminated with both kinds of coliforms. The results demonstrated that the application of reuse water for agricultural purposes should be treated in a very carefully way, so as to be possible and to contribute to its sustainability.