Effects Of Wastewater Application Research Articles

Domestic wastewater infiltration process in desert sandy soil and its irrigation prospect analysis

Although domestic wastewater and its reclaimed water are alternative water resources in arid region, investigation of their negative effect must be done to prevent environmental pollution. In this paper, a short-term column experiment was conducted to simulate the infiltration process of wastewater in desert soil. Alfalfa was planted and irrigated with fresh water for control (CK), tertiary treated domestic wastewater (TTW), secondary treated domestic wastewater (STW) and raw domestic wastewater untreated (RW). The effect of wastewater application on desert soil, drainage and plant properties was evaluated. Experimental results demonstrated that the tested desert soil has no soil structure, organic matter, nor microbial community while possess high infiltration rate. The use of wastewater significantly improved plant growth, and the biomass of TTW, RW, STW were 5.5, 4.3, 2.9 times of CK. The infiltration rate of water in bare soil was high (high to low: TTW, CK, RW, STW), while plant growth reduced infiltration rate (ca. 40% with TTW and RW). Wastewater irrigation and plant growth decreased soil zeta potential, while increased formation of aggregates and bacterial abundance and diversity in soil. Top soil (0–30 cm) accumulation of nitrogen (N), phosphorus (P), organic matter and E. coli was evidenced and all could go down to deep soil and drainage with constant wastewater use. It was concluded that domestic wastewater had big potential in desert soil vegetation recovering and function restoration. Nevertheless, the N, salt, P and organic matter and E. coli in wastewater could give rise to desert soil and groundwater contamination if improper treatment was used.

Physicochemical Properties of Soil under Wheat Cultivation by Irrigation with Municipal Wastewater in Bangladesh

ABSTRACTIrrigation with wastewater provides the opportunity to solve the problems of its disposal, reuse and water conservation. Freshwater, differentially diluted wastewater and undiluted wastewater (hereafter called wastewater) were used to grow wheat in sandy loam soil under fertilized and unfertilized conditions at the experimental farm of Bangladesh Agricultural University, Bangladesh. Fresh groundwater and wastewater of Mymensingh municipality were used to irrigate a wheat field for three consecutive years to examine the effects of wastewater application on soil properties. In this study, the properties of wastewater-irrigated soil were compared with freshwater-irrigated soil. The application of wastewater reduced the bulk density of the surface soil by 1.92% and augmented the porosity by 5.89%. The unsaturated hydraulic conductivity and water retention capacity of the soil were improved under wastewater irrigation. Soil pH increased due to wastewater application but decreased, to a smaller extent, due to fertilizer application. Soil electrical conductivity (EC) increased both with wastewater and with fertilizer application; both parameters changed significantly in the 0–20 cm soil layer. However, at the deeper layers, they were not affected by wastewater application. The organic carbon (C) and total nitrogen (N) level of the soils were higher under wastewater irrigation than under freshwater-irrigated soil. The organic C increased by 23.93% under wastewater irrigation in the top 20 cm soil layer. The N content of the soil showed similarities with the organic C contents. Available P and S concentrations were greater in the soil irrigated with wastewater compared with the soil irrigated with freshwater. The exchangeable cations – sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg) – also increased significantly with wastewater application. Thus, farmers are advised for irrigation with municipal wastewater to ease pressure on freshwater and to improve soil fertility.

New Conceptual Model for Soil Treatment Units: Formation of Multiple Hydraulic Zones during Unsaturated Wastewater Infiltration

Onsite wastewater treatment systems are commonly used in the United States to reclaim domestic wastewater. A distinct biomat forms at the infiltrative surface, causing resistance to flow and decreasing soil moisture below the biomat. To simulate these conditions, previous modeling studies have used a two-layer approach: a thin biomat layer (1-5 cm thick) and the native soil layer below the biomat. However, the effect of wastewater application extends below the biomat layer. We used numerical modeling supported by experimental data to justify a new conceptual model that includes an intermediate zone (IZ) below the biomat. The conceptual model was set up using Hydrus 2D and calibrated against soil moisture and water flux measurements. The estimated hydraulic conductivity value for the IZ was between biomat and the native soil. The IZ has important implications for wastewater treatment. When the IZ was not considered, a loading rate of 5 cm d resulted in an 8.5-cm ponding. With the IZ, the same loading rate resulted in a 9.5-cm ponding. Without the IZ, up to 3.1 cm d of wastewater could be applied without ponding; with the IZ, only up to 2.8 cm d could be applied without ponding. The IZ also plays a significant role in soil moisture distribution. Without the IZ, near-saturation conditions were observed only within the biomat, whereas near-saturation conditions extended below the biomat with the IZ. Accurate prediction of ponding is important to prevent surfacing of wastewater. The degree of water and air saturation influences pollutant treatment efficiency through residence time, volatility, and biochemical reactions.

Effects of alternate use of wastewater and fresh water on soil saturated hydraulic conductivity

The objective of this research was to study the effects of alternate uses of wastewater with different cycles (one, two and three) and fresh water on the saturated hydraulic conductivity of surface layer (Ks) as relative Ks (Kr1) in sandy loam, loam and clay loam soils. The results showed that the reduction in Kr1 mainly occurred in the surface layer due to the application of wastewater. This effect is more pronounced in clay loam soil than in loam and sandy loam soils, especially with three cycles of wastewater application. The application of fresh water after one and two cycles of wastewater improved the value of Kr1. Improvement of Kr1 by fresh water application after three cycles of wastewater is not pronounced. Therefore, it is recommended to use fresh water after two cycles of wastewater in order to prevent the deterioration of soil Ks. It is concluded that the fresh water application is more effective in sandy loam soil than in loam and clay loam soils in improving the Kr1 reduction due to the wastewater application. The effect of wastewater application on the reduction of Kr in the subsurface layer (Kr2) is less than those obtained for the surface layer. The reductions in Kr2 in the subsurface layer are about half of those obtained on the surface layer (Kr1).

Effects of wastewater application on saturated hydraulic conductivity of different soil textures

AbstractAs metropolitan areas expand, the municipal and industrial uses of freshwater increase. Therefore, water resources for irrigation become limited and wastewater reuse for irrigation becomes a good alternative. For this purpose, the effects of suspended solids in wastewater on the soil physical properties, i.e., saturated hydraulic conductivity, Ks, have to be considered. The objectives of this research were to study the effects of applying freshwater and differently treated wastewater on Ks in the surface and subsurface layers of sandy‐loam, loam, and clay‐loam soils. This effect was studied by investigating the ratio of Ks for wastewater to Ks for fresh water in soil surface as Kr1 and in soil subsurface as Kr2. The results showed that the application of freshwater did not reduce the Kr1 considerably. However, the reduction in Kr1 mainly occurred in soil depth of 0–50 mm due to the application of wastewater. This effect is more pronounced in clay‐loam soil than in loam and sandy‐loam soils. It is concluded that application of wastewater with TSS (total suspended solid) of ≥ 40 mg L–1 resulted in Kr1 reduction of >50% in different soil textures. However, the Kr2 reduction at soil depth of 100–300 mm is not considerable by application of wastewater for different soil textures. Further, it is concluded that less purified wastewater can be used in light‐texture soils resulting in less reduction in Kr1. Empirical models were developed for predicting the value of Kr1 as a function of amounts of wastewater application and TSS for different soil textures that can be used in management of wastewater application for preventing deterioration of soil hydraulic conductivity.

Changes in soil characteristics during landfill leachate irrigation of Populus deltoides

The effects of wastewater application on electrical conductivity, water retention and water repellency of soils planted with Populus deltoides (eastern cottonwood) and irrigated with different concentrations of landfill leachate and compost wastewater, tap water and nutrient solution were evaluated. Substrate water content at field capacity (−0.033 MPa) and at permanent wilting point (−1.5 MPa) was determined with a pressure plate extractor to assess available water capacity of the substrate. A water drop penetration test was used to determine substrate water repellency. The biomass of nutrient and landfill leachate treatments was significantly ( P < 0.05) greater compared to the tap water and compost wastewater treatments. All treatments increased substrate water content at field capacity and at permanent wilting point. Landfill leachate significantly increased available water capacity (up to 52%); treatment with compost wastewater significantly decreased it (25–47%). All substrates showed increased water repellency after the experiment at field capacity and permanent wilting point comparing to the original substrate. The strongest influence on water repellency at both field capacity and permanent wilting point showed irrigation with compost wastewater and tap water. Pronounced influence on substrate’s water repellency of compost wastewater could be contributed to a high content of dissolved organic carbon, whereas Mg and Ca cations caused flocculation and consequent water repellency of the substrate irrigated with tap water. The results indicate that soil physical characteristics must be closely monitored when landfill leachate and compost wastewater are used for irrigation to avoid long term detrimental effects on the soil, and consequently on the environment. Due to the complexity of the compost wastewater quality the latter should be applied on open fields only after prior pre-treatment to reduce dissolved organic carbons, or alternatively, compost wastewater should be added only intermittently and in diluted ratios.

Effects of Waste Water Application on Heavy Metals (Mn, Fe, Cr and Cd) Contamination in a Black Locust Stand in Semi-Arid Zone of Iran

Effects of Waste Water Application on Heavy Metals (Mn, Fe, Cr and Cd) Contamination in a Black Locust Stand in Semi-Arid Zone of Iran

Deslocamento miscível de nitrato e fosfato proveniente de água residuária da suinocultura em colunas de solo

A fertirrigação com águas residuárias da suinocultura vem sendo muito difundida no País, principalmente na região sul do Brasil, entretanto, o alto potencial poluidor dos dejetos pode tornar-se uma ameaça de contaminação de solos e águas superficiais e subterrâneas se utilizados em quantidades excessivas. Neste trabalho o objetivo principal foi avaliar o processo de lixiviação de íons nitrato e fosfato em colunas de solo, obtendo-se os coeficientes de dispersão hidrodinâmico e o fator de retardamento para a determinação do potencial de contaminação dos lençóis de água subterrâneos. Verificou-se, ainda, o efeito da aplicação de águas residuárias da suinocultura tratada com reatores anaeróbios sobre as propriedades físico-químicas do solo, cujos resultados indicaram que o potencial de contaminação dos lençóis de água subterrâneos pelo íon nitrato é elevado, ao contrário do que ocorre com o íon fosfato, que apresentou baixo potencial de contaminação em função da sua alta reatividade.

Wastewater Effluents from a Tannery: Their Effects on Soil and Vegetation in Pakistan

The wastewater of Firdaus Tanneries, Muridke, Pakistan, was very highly saline and very highly sodic (water-quality class: C4-S4). It was being used for irrigating fields near the Tanneries but there was a piece of wasteland which, because of its elevation, could not receive this water. The vegetation of this wasteland and that of the irrigated field was studied.The effects of wastewater application on characteristics of the soil were studied in the irrigation field and, for comparison, also in the wasteland soil. The soil samples were taken from the surface and from 5, 10, and 20 cm depths. Moisture content, water-stable aggregates, water-holding and cation-exchange capacities, amounts of organic matter, and exchangeable sodium, were greater in the irrigated field as compared with wasteland soil at each corresponding soil-depth. Electrical conductivity, pH, and the amounts of calcium, magnesium, soluble sodium, chlorides, sulphates, and the values of Sodium Adsorption Ratio and Exchangeable Sodium Percentage, were significantly higher in wasteland as compared with those in the irrigated field at each corresponding soil-depth. These values tended to decrease from the surface to 20 cm soil depth in each site.