Effects Of Effluent Irrigation Research Articles

Agricultural utilization of treated sewage effluent: Experience from Brazil

Prospects for wastewater irrigation in Brazil look promising, in light of the fact that agriculture plays an essential role in the country's economy and, furthermore, freshwater for irrigation is scarce in some parts of the country. However, irrigation with effluents still represents a new practice, and most available data related to the benefits and risks of effluent irrigation are based on short-term experiments. The present paper provides an overview of the potential of water reuse in Brazil; it describes the main results concerning effects of effluent irrigation on soil/plant interactions in Brazil, and discusses some important issues that require further investigation. So far, research in Brazil has been mainly focused on soil chemical changes that follow effluent application, while investigations concerning the occurrence and fate of trace contaminants, and the potential risks they present, remain to be carried out. Such contaminants include heavy metals and pharmaceutically active products. Effluent irrigation of agricultural crops intended for biofuel production represents a strategic issue, of increasing importance for the national and international market. For a consistent evaluation of long-term benefits and risks of effluent irrigation in this country, major needs are: improvement of the sewage collection and treatment infrastructure; establishment of legal regulations to control water reuse in agriculture; and permanent monitoring of areas already under wastewater irrigation.

Treated domestic sewage irrigation effects on soil hydraulic properties in arid and semiarid zones: A review

In arid and semiarid regions, the use of treated domestic sewage (effluent) for irrigation is becoming a common practice, because of the shortage of freshwater resources. However, the use of effluent for irrigation could have an impact on the chemical and hydraulic properties of soils. This paper reviews the effects of irrigation with effluents that have undergone various treatments on hydraulic properties of semiarid and arid soils. Irrigation of semiarid clay and sandy soils with secondary effluent increased the salinity at depths down to ∼1.5 m, and the sodicity down to ∼1.5 and >4 m, respectively. The increase of the organic matter load in the effluents resulted in inconsistent effects on the organic matter content of the topsoil, but it could lead to its decrease in the subsoil because of a “priming effect” of the effluent. Percolation of effluent through the soil profile can reduce its saturated hydraulic conductivity ( K s ) to an extent that depends on the effluent quality, soil chemical properties, and the pore size distribution in the soil. Leaching a loamy and a clay soil with secondary effluent decreased the K s because of plugging of the pores with suspended solids, whereas the K s of a sandy soil was not affected because of its large average pore size. Irrigation of high sodicity, arid soils with effluent that had undergone reverse osmosis treatment decreased K s because of the low electrolyte concentration of the effluent, which enhanced soil swelling and clay dispersion. An increase of soil sodicity, caused by effluent irrigation, decreased the K s of a clay soil leached with water of low electrolyte concentration, as a result of enhanced clay swelling and dispersion. In a non-calcareous, sandy soil, the higher sodicity in the effluent-irrigated soil led, under rainfall conditions, to enhanced seal formation, reduced infiltration, and increased runoff, as a result of enhanced clay dispersion. In contrast, for calcareous soil under similar conditions, no effect of effluent irrigation on runoff and soil loss was observed. This was, probably, because of the release of Ca during the dissolution of CaCO 3; this Ca replaced exchangeable Na, thereby reducing the soil sodicity to its natural levels. Because of the interaction between effluent irrigation and soil properties, it is necessary to identify sensitive regions and soils prior to irrigation with effluents, to prevent possible deleterious effects on soil structure and hydraulic properties.

Soil exchangeable cations, sugarcane production and nutrient uptake after wastewater irrigation

Wastewater irrigation may benefit agricultural crops with water and essential nutrients (mainly nitrogen), also affecting soil chemistry. The effects of effluent irrigation on yield, stalk nutrient uptake and on soil chemistry over 16 months were studied in a sugarcane (Saccharum spp.) crop growing on an Oxisol in Lins, State of São Paulo, Brazil. Irrigated plots received 50% of the recommended mineral-N fertilization and 100, 125, 150 or 200% of the crop water demand, while control plots received neither additional N nor water. The high sodium content of effluent resulted in Na inputs as high as 6.2 t ha-1, along with 1497 kg N ha-1 and 628 kg K ha-1. All the effluent plots except the T125 treatment had higher yields (up to 247 t ha-1) than the control (153 t ha-1). Significant amounts of N (up to 597 kg ha-1) and K (up to 546 kg ha-1) were exported by the plant harvest. Additions of nutrients and Na via irrigation were not compensated by stalk growth, causing a low recovery of N, P, Ca, Na, and showing the relative over N fertilization of the crop. Changes in soil pH, H + Al, Ca, Mg and K were small, whereas Na accumulated over time with irrigation. The treated wastewater irrigation is expected to gain increased importance, requiring careful considerations involving the adequate balance between nutritional inputs via irrigation and optimal plant productivity requirements.

Long-term impacts of pasture irrigation with treated sewage effluent on nutrient status of a sandy soil in Zimbabwe

Declining freshwater resources and the need to safely dispose wastewater have led to a rapid increase in wastewater reuse in developing countries. However, empirical evidence on the effects of effluent-irrigation on soil fertility is limited. The study investigated the nutrient status of a sandy soil after 26 years of effluent irrigation. Soil samples from effluent-irrigated and non-irrigated sites were analysed for pH, electrical conductivity (EC), soil organic carbon (SOC), total and plant available forms of N and P, exchangeable bases and trace metals. Analysis of effluent quality showed that, besides Cr and Cd, all measured parameters were within acceptable limits for wastewater irrigation. Our results revealed that effluent-irrigation significantly (P < 0.05) enriched the soil with essential nutrients for plant growth, which are commonly deficient in most soils of Zimbabwe. Effluent-irrigated soils had significantly (P < 0.05) higher pH, EC, SOC, total and available N and P and, exchangeable Ca and Mg at 0–30 cm-depth. However, apart from Cr accumulation, effluent irrigation significantly (P < 0.05) depleted Zn, Cu and Cd probably due to plant uptake and enhanced mobility under acidic soil pH. Cr accumulation and depletion and mobility of Zn, Cu and Cd in effluent-irrigated soils could threaten the sustainability of the practice. We recommend a review of the current management practices based on crop water requirements, effluent quality and environmental considerations.

Effects of Effluent Irrigation on Seal Formation, Infiltration, and Soil Loss during Rainfall

The use of effluent for irrigation could affect the chemical and hydraulic properties of soils due to its high salt and organic matter (OM) content, and, consequently, the rainfall–infiltration–runoff–erosion relationships during the subsequent rainy season. This study investigates the effects of long‐term effluent irrigation on soil chemical properties, seal formation, infiltration, and soil loss under rainfall. Simulated rainfall (85 mm) was applied to (i) air‐dried or (ii) prewetted clay and sandy soils from plots that had been irrigated with fresh water (FW) or effluent for &gt;10 yr. Effluent irrigation increased the total OM content and the exchangeable sodium percentage (ESP) of the soils. The cumulative infiltration in FW‐ and effluent‐irrigated clay soils was 6.5 and 5.6 mm, respectively, in the initially dry soils, and 52.3 and 51.5 mm, respectively, in the prewetted soils. In the FW‐ and effluent‐irrigated sandy soils, the corresponding values of cumulative infiltration were 79.5 and 44.7 mm, and 85.0 and 56.3 mm, respectively. In the sandy soil, the higher sodium adsorption ratio (SAR) values in the leachate of effluent‐irrigated soil led to greater clay dispersion, which enhanced seal formation, reduced infiltration, and increased soil loss. In the clay soil, slaking was the main process involved in seal formation, neglecting the possible deleterious effect of effluent irrigation. When slaking was prevented, the SAR values in the leachate of the effluent‐irrigated soil decreased during rainfall and were similar to those of the FW‐irrigated soil at the end of the applied rainfall amount. This was probably due to the exchange of adsorbed Na with soluble Ca, which minimized the differences in clay dispersion, infiltration, and soil loss. Therefore, in the clay soil, aggregate slaking might be the main process involved in seal formation and affecting infiltration and erosion. These results show that the effect of effluent irrigation on infiltration, runoff, and soil loss depends on the soil type (amount of clay and CaCO3) and the dominant mechanisms of seal formation. Therefore, to prevent a possible deleterious effect on soil structure, it is necessary to identify sensitive areas and soils before the application of effluents for irrigation.

1. Research developments and case studies

Summary In Australia, research on the irrigation of trees with effluents commenced in the 1970s. Initial trials tested the survival and early growth of more than 60 native and exotic species irrigated with municipal effluent. Later work has concentrated on species from the genera Eucalyptus. Casuarina, Pinus and Populus, with the most detailed research being conducted with Pinus radiata (radiata pine). Aspects studied so far include the effects of effluent irrigation on tree production, wood quality, nutrition, photosynthesis, transpiration, and changes in soil properties. There are now several projects across Australia where tree plantations are being irrigated with recycled water at an operational level. Described in this paper are three case studies: first, a 30 ha plantation of Populus spp. (poplars) established in 1980 in Victoria; second, a 20 ha plantation of Eucalyptus spp. (eucalypts) established in 1984 in South Australia; and third, a 25 ha plantation of E. camaldulensis (river red gum) establi...