Wastewater Reuse For Irrigation Research Articles

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.

Soil DNA evidence for altered microbial diversity after long-term application of municipal wastewater

Water resources constitute a social, agricultural and economic problem in most countries of the southern Mediterranean Basin. Alternative strategies have been developed such as the reuse of municipal wastewater for irrigation in agriculture. Despite numerous advantages for soil fertility and crop productivity, recycling wastewater in soils also has several ecotoxicological and sanitary problems. Few investigations have assessed the risk by evaluating the impact of wastewater irrigation on soil microbes. Here, we report for the first time the short- and long-term effects of treated municipal wastewater irrigation on the density and genetic structure of bacterial and fungal soil communities. Soils from agricultural sites in Tunisia that had been irrigated with wastewater for 4, 8, 16 and 26 years were characterised. Soil physicochemical and microbial characteristics were assessed by sampling at 0–20 and 20–40 cm depth at each site. Quantitative changes in bacterial and fungal communities were measured by indirect counts on synthetic culture media and qualitative modifications were evaluated by using molecular ecology methods: B- and F-ARISA for Bacterial and Fungal Automated Ribosomal Intergenic Spacer Analysis, respectively. These methods allowed genotyping the structure of bacterial and fungal communities from soil DNA extracts. Our results revealed a significant increase in microbial densities related to the duration of irrigation with wastewater. In addition, wastewater irrigation led to changes in the genetic structure of bacterial and fungal communities, the magnitude and specificity of these changes being significantly correlated with the duration of such irrigation. These results show that wastewater management schemes have a major effect on indigenous microbial abundance and composition in soils that could be related to the recurrent inputs of organic compounds and mineral/metallic elements. In an agro-ecological context, irrigation with municipal wastewater represents an impacting practice that now needs to be evaluated more fully in terms of ecosystem services for sustainable agriculture.

Regional Planning of Wastewater Reuse for Irrigation and River Rehabilitation

Abstract Subject to a few agri‐environmental restrictions, municipal wastewater can be utilised for agricultural irrigation and river rehabilitation. This paper develops a single‐year Planning Model for a region in Israel which consists of a city and three potential wastewater consumers. The model incorporates, in one endogenous system, the economic, physical and biological relationships in the water–soil–plant–environment system and its objective is to maximise the regional social welfare. The model determines the optimal crop mix and the optimal allocation of the limited water and land resources among all potential users. Then, different allocation approaches from the concept of transferable utility games are applied to determine a reasonable and fair allocation of the additional net benefits which will be acceptable to all the players. The results support the collaboration among the economic entities and indicate economic and environmental advantages which can serve the decision‐makers.

Comparative reductions of bacterial indicators, bacteriophage-infecting enteric bacteria and enteroviruses in wastewater tertiary treatments by lagooning and UV-radiation

A two-year monitoring program of microbiological and physical-chemical parameters at 2 waste water treatment plants (WWTPs) in Mallorca (Spain) was performed in order to (1) evaluate the efficiency of lagooning and UV radiation as tertiary treatment processes; (2) determine the characteristics of wastewater effluent for its potential agricultural reuse; and (3) establish correlations between bacteriological and virological parameters. The presence of currently established bacterial indicators (total coliforms, faecal coliforms, Escherichia coli, enterococci, and spores of sulphite-reducing clostridia), virological (enteroviruses, somatic coliphages, F-specific coliphages, and phages infecting Bacteroides fragilis and Bacteroides thetaiotaomicron), and helminth eggs were tested during this study. Bacterial and viral indicators were removed at least with one log reduction in the lagooning system, and to a lesser extent with UV-radiation treatment. The lagooning system was less efficient in removing phages and viruses than were bacterial indicators, with the exception of F-specific phages. Phages of B. fragilis and B. thetaiotaomicron were less removed than all of the other microbiological parameters. In the UV-radiation treatment, however, the faecal coliforms proved the most sensitive, while clostridial spores, somatic coliphages, Bacteroides phages, and enteric viruses were the more resistant. Helminth eggs were not detected in any samples from effluents of either the secondary or tertiary treatments.Indicator levels in both treatments met the established regulations of both local and national authorities for the disposal or reuse of wastewater in irrigation for non-human crop. We demonstrate that somatic coliphages are effective indicators of enteric viruses in both of the WWTPs studied.

Small scale recirculating vertical flow constructed wetland (RVFCW) for the treatment and reuse of wastewater

The quantity of freshwater available worldwide is declining, revealing a pressing need for its more efficient use. Moreover, in many developing countries and lightly populated areas, raw wastewater is discarded into the environment posing serious ecological and health problems. Unfortunately, this situation will persist unless low-cost, effective and simple technologies are brought in. The aim of this study is to present such a treatment method, a novel setup which is termed recirculating vertical flow constructed wetland (RVFCW). The RVFCW is composed of two components: (i) a three-layer bed consisting of planted organic soil over an upper layer of filtering media (i.e. tuff or beads) and a lower layer of limestone pebbles, and (ii) a reservoir located beneath the bed. Wastewater flows directly into the plant root zone and trickles down through the three-layer bed into the reservoir, allowing passive aeration. From the reservoir the water is recirculated back to the bed, several times, until the desired purification is achieved. The results obtained show that the RVFCW is an effective and convenient strategy to treat (domestic, grey and agro) wastewater for re-use in irrigation. The system performance is expected to be further improved once current optimization experiments and mathematical modeling studies are concluded.

Simple digestion procedure followed by the azomethine-H method for accurate boron analysis and discrimination between its fractions in wastewater and soils

Excess boron is a growing environmental problem. It often affects agricultural yields, where reuse of wastewater for irrigation is practiced. This problem raises the need for reliable, simple and economical methods to monitor boron concentrations in wastewater and soil extracts. One such method, the commonly used azomethine-H spectrophotometric method, suffers from color interference, originating from high concentrations of dissolved organic matter, when applied to many wastewater and agricultural soil extracts. Moreover, this method only quantifies free dissolved boron and lacks the ability to quantify boron that is adsorbed to either the dissolved organic matter or suspended solids that are present in the sample. This work suggests a modification of the standard azomethine-H method, in which the solution is digested with potassium persulfate prior to the standard procedure. We show that this pretreatment can overcome the color interference and lead to highly accurate and precise boron analyses in wastewater. In soil extracts, the boron concentrations obtained using the suggested procedure were better correlated to inductively coupled plasma (ICP) spectrometry results than those measured by the standard method, because whereas the standard method quantifies the free dissolved boron only, the modified method, like the ICP method, quantifies the total dissolved boron in the sample. Thus, the suggested modification can be used to quantify the respective distributions of free dissolved boron, boron adsorbed to dissolved organic matter and boron adsorbed to suspended solids in soil extracts and water samples.

Pot experiment of treated domestic wastewater re-use for irrigation of Chinese cabbage

Pot experiment of treated domestic wastewater re-use for irrigation of Chinese cabbage

Nutrient flows in small-scale peri-urban vegetable farming systems in Southeast Asia—A case study in Hanoi

In many peri-urban areas of Southeast Asia, land use has been transformed from rice-based to more profitable vegetable-based systems in order to meet the increasing market demand. The major management related flows of nitrogen (N), phosphorus (P), potassium (K), copper (Cu) and zinc (Zn) were quantified over a 1-year period for intensive small-scale aquatic and terrestrial vegetable systems situated in two peri-urban areas of Hanoi City, Vietnam. The two areas have different sources of irrigation water; wastewater from Hanoi City and water from the Red River upstream of Hanoi. The first nutrient balances for this region and farming systems are presented. The main sources of individual elements were quantified and the nutrient use efficiency estimated. The environmental risks for losses and/or soil accumulation were also assessed and discussed in relation to long-term sustainability and health aspects. The primary source of nutrient input involved a combination of chemical fertilisers, manure (chicken) and irrigation water. A variable composition and availability of the latter two sources greatly influenced the relative magnitude of the final total loads for individual elements. Despite relatively good nutrient use efficiencies being demonstrated for N (46–86%) and K (66–94%), and to some extent also for P (19–46%), high inputs still resulted in substantial annual surpluses causing risks for losses to surface and ground waters. The surplus for N ranged from 85 to 882 kg ha −1 year −1, compared to P and K which were 109–196 and 20–306 kg ha −1 year −1, respectively. Those for Cu and Zn varied from 0.2 to 2.7 and from 0.6 to 7.7 kg ha −1 year −1, respectively, indicating high risk for soil accumulation and associated transfers through the food chain. Wastewater irrigation contributed to high inputs, and excess use of organic and chemical fertilisers represent a major threat to the soil and water environment. Management options that improve nutrient use efficiency represent an important objective that will help reduce annual surpluses. A sustainable reuse of wastewater for irrigation in peri-urban farming systems can contribute significantly to the nutrient supply (assuming low concentrations of potential toxic or hazardous substances in the water). Nutrient inputs need to be better related to the crop need, e.g. through better knowledge about the nutrient concentrations in the wastewater and improved management of the amount of irrigation water being applied.

Potential for wastewater reuse in irrigation: case study from Aden (Yemen)

Wastewater treatment with waste stabilization ponds (WSP) is a very efficient, low cost and low maintenance operation. The treated wastewater from WSP should be considered as a valuable resource for reuse by water resources managers. Yemen’s water resources are currently experiencing a crisis, because all surface water and groundwater resources are exploited beyond the level of recharge. Promoting water reuse of treated wastewater for irrigation could mitigate this water crisis. This paper assesses the performance of a WSP in the city of Aden by examining the quality of treated sewage predominantly of domestic origin. A comparison with international guidelines reveals that it is possible to use the final effluent to a limited extent in irrigation. This paper includes an outline of the social, religious and political reasons for the water crisis, and explores the idea of reuse of effluent for different irrigation practices.

Wastewater Re-Use and Groundwater Quality edited by Joop Steenvoorden & Theodore Endreny . 2004, IAHS Publication no 285, £30, 112 pp. ISBN 1-901502-52-X

The global need for a good supply of high quality drinking water is not only increasing with population but with a rise in income. The availability of such a supply of potable water is already uncertain over a large percentage of the world but the uncertainty is exacerbated by factors such as global warming. The reuse of wastewater for irrigation is one solution to meet this need – where the world population is expected to increase by 2 billion in 20 years – but there are obvious concerns over health issues with the use of untreated wastewater. The book …

Source Bioaerosol Concentration and rRNA Gene-Based Identification of Microorganisms Aerosolized at a Flood Irrigation Wastewater Reuse Site

Reuse of partially treated domestic wastewater for agricultural irrigation is a growing practice in arid regions throughout the world. A field sampling campaign to determine bioaerosol concentration, culturability, and identity at various wind speeds was conducted at a flooded wastewater irrigation site in Mexicali, Baja California, Mexico. Direct fluorescent microscopy measurements for total microorganisms, culture-based assays for heterotrophs and gram-negative enteric bacteria, and small-subunit rRNA gene-based cloning were used for microbial characterizations of aerosols and effluent wastewater samples. Bioaerosol results were divided into two wind speed regimens: (i) below 1.9 m/s, average speed 0.5 m/s, and (ii) above 1.9 m/s, average speed 4.5 m/s. Average air-borne concentration of total microorganisms, culturable heterotrophs, and gram-negative enteric bacteria were, respectively, 1.1, 4.2, and 6.2 orders of magnitude greater during the high-wind-speed regimen. Small-subunit rRNA gene clone libraries processed from samples from air and the irrigation effluent wastewater during a high-wind sampling event indicate that the majority of air clone sequences were more than 98% similar to clone sequences retrieved from the effluent wastewater sample. Overall results indicate that wind is a potential aerosolization mechanism of viable wastewater microorganisms at flood irrigation sites.

Semi-intensive treatment plants for wastewater reuse in irrigation

Semi-intensive technologies are a middle term between intensive ones (e.g., activated sludge with a retention time of hours) and extensive ones (e.g., stabilization ponds with a retention time of several weeks). The most common semi-intensive configuration used in Israel is made of anaerobic ponds followed by aerated lagoons. These small low-energy units remove about 75-80% of the BOD and are followed by wastewater reservoirs for storage and complementary treatment. The reduction in loading allows a flexible operation of the reservoirs for the removal of other pollutants, while providing storage capacity to cope with the changes in water demand for irrigation during the year. In schemes for wastewater reuse in irrigation, this lay-out has proved to be low-cost, low-energy, flexible, reliable and efficient. Variations of this basic configuration are the use of UASB reactors instead of anaerobic ponds, aerated lagoons in series or low-rate trickling filters instead of aerated lagoons, constructed wetlands or rock-filters for algae removal, etc. Semi-intensive technologies use less energy than intensive ones, and less land than extensive ones. They can remove as much BOD as intensive ones, and as much pathogens and refractory pollutants as extensive ones. They release no or very small amounts of sludge.

Expert system for municipal wastewater management with emphasis in reuse

This paper presents a methodology that uses a knowledge base and inference procedures for developing rational wastewater management schemes for small to medium size communities with emphasis in the protection of human health, the reuse of treated wastewater, and the pollution minimization of water receivers. The system provides an optimal year-round treatment/reuse/disposal plan, which maximizes the wastewater reuse for irrigation, meets the applicable minimum municipal wastewater treatment requirements and observes the water quality standards of receivers with the minimum treatment costs. The solution is dynamic in the sense that varying monthly design values can be assigned to the input variables used in the computation of irrigation requirements, assimilative capacity of receivers and performance of natural systems. The above procedure shows that the use of multiple receivers over the year is often highly advantageous; combining for example the increased treatment efficiency and reuse potential for irrigation during summer with the increased assimilative capacity of a river during winter. The expert system incorporates a number of design and ambient quality models, for which graphical solutions have been developed, so as to enable manual application if desired. The entire procedure is implemented in an integrated computer program that facilitates and refines problem solution. The expert system provides interactive guidance for collecting the necessary field information. Finally, the results of a case study for the management of wastewaters from the six communities of the Municipality of Keramoti are presented.

Treatment of domestic sewage in a combined UASB/RBC system. Process optimization for irrigation purposes

A Rotating Biological Contactor (RBC) was fed with raw domestic wastewater or anaerobic effluents. The experiments were conducted at increasing operational temperatures viz. 11, 20 and 30 degrees C to assess the potential increase in removal efficiencies for the different COD fractions (COD(total), COD(suspended), COD(colloidal) and COD(soluble)), E. coli and in the nitrification rate. The results clearly show that, the RBC at HRT of 2.5 h and OLR of 47 g COD/m2 x d provided a very high residual COD(total) value of 228 mg/l when treating domestic wastewater. This was not the case as compared to the results obtained for the system when operated at the same HRT but at lower OLR's of 27, 20 and 14.5 g COD/m2 x d with a UASB effluent at operational temperatures of 11, 20 and 30 degrees C respectively. The residual COD(total) values amounted to 100, 85 and 72 mg/l in the final effluents. Moreover, a high removal of ammonia and low residual values of E. coli was found for the RBC when treating a UASB effluent at operational temperature of 30 degrees C as compared to the situation for treatment of domestic wastewater and UASB effluent at lower temperatures of 11 and 20 degrees C. It can be concluded that an efficient pre-treatment of sewage implies a substantial reduction of OLR applied to the RBC and consequently improves the residual of COD(total) ammonia and E. coli in the final effluent. Therefore, this study supports using a combined system UASB/RBC for treatment of domestic wastewater for reuse in irrigation.

Wastewater reuse in Italy

In many parts of Italy, particularly in the South, it has become ever more difficult to meet the water demand. The recent years of drought and the constant increase of water demand for the civil sector have made irrigation supply more problematic. Wastewater reuse could represent a viable solution to meet water demand. The focus of this paper is on the regulation problems, hampering the development of wastewater reuse for irrigation, and on the potentials for reuse, particularly in Southern Italy. Planned exploitation of municipal wastewater could help meeting the irrigation water demand particularly in Southern Italy, where farmers have been practising uncontrolled wastewater reuse for a long time. In Northern and Central Italy, where available water resources generally meet water needs for different purposes, wastewater reuse could play an important role in controlling the pollution of water bodies. Despite the fact that Italian legislation is extremely strict and outdated, for several years in some regions, such as Sicily, wastewater reuse systems have been in operation; furthermore, several projects of wastewater reuse are currently in progress.

Purification of rotating biological contactor (RBC) treated domestic wastewater for reuse in irrigation by biofilm channel

Abstract Total nitrogen (TN-N) below 10 mg l −1 was suggested for short-term irrigation application in Taiwan. TN-N in the treated effluent of a Rotating Biological Contactor (RBC) system was about 18 mg l −1 and further reclamation was required for reuse purpose. A channel with nine sections, 6 m long, 30 cm in width and 20 cm in height, with plastic sheets as a biofilm carrier inserted inside, was set up at a wastewater treatment plant site to test the purification efficiency. Six different flow velocities were tested in this research. The nitrogen conversion rate increased with velocity until an optimal velocity of 1 cm s −1 was reached. The kinetic constants of Total Kjeldahl nitrogen (TKN) and TN-N were found to be 4.57 and 7.51 (mg l −1 h −1 ). The unit area biofilm carrier removal rates for TKN and TN-N were found to be 1.34 and 2.20 (g m −2 d −1 ) and the unit volume removal rates for TKN and TN-N were 140.72 and 231.18 (g m −3 d −1 ), respectively, at this optimal velocity. The TKN and TN-N concentrations kinetic rates fit a zero-order approach. The TN-N concentration criterion of 10 mg l −1 was found to be possible with this biofilm channel.

Pilot plant for reclaimed wastewater reuse in nurseries

In this paper, after a brief introduction on irrigation wastewater reuse, we take a closer look at Pistoia, the most important nursery area in Italy, which specializes in production of woody ornamental plants. Groundwater resources are used for irrigation in competition with urban use, causing serious shortage problems in summer. Treated municipal wastewater can be a good alternative source of water and fertilizer nutrients for ornamental plant production. During 1998, we carried out an experiment along with local corporate bodies to evaluate the effects of Pistoia's wastewater treatment plant (WWTP) effluent irrigation of the (Pistoia) area – compared with traditional well water irrigation – on three container-grown species, each of them characterized by different growth habits. Plants irrigated with the effluent, treated with UV irradiation in a disinfection pilot plant, showed better physiological and growth parameters than those irrigated with traditional well water.

A study of selected pathogens in municipal wastewater treatment plant effluents

Wastewater reuse for irrigation increases the prevalence of health infections. Sixteen of the municipal wastewater treatment plants in Jordan, operated directly by the Government of Jordan, and others operated by the private sector are represented in this study which lasted for four years. Samples were collected from the effluents of these plants and were analysed for their content of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total fecal coliform count (TFCC), and parasites (protozoa and helminthes). The study concluded that the effluents of these plants are classified as moderate in strength in terms of BOD, COD, and TSS. It was also concluded based on the BOD, COD, TFCC and TSS results that the effluents of the treatment plants included in the study can be reused for irrigation purposes ranging from unrestricted irrigation to irrigation for animal feed. The results of TFCC indicated that the treated effluents of the treatment plants can be reused for irrigation for different purposes ranging from cooked vegetables to trees and pastures, and for dams and reservoirs. Results of the parasites content indicated that these effluents contain serious levels of parasites and cannot be reused to irrigate raw eaten vegetables. The study also provided recommendations to improve the performance of the treatment plants in terms of parasites removal.

The effect of waste water reuse in irrigation on the contamination level of food crops by Giardia cysts and Ascaris eggs

In Marrakech, raw sewage has been used for farming purposes for several decades for many types of crops. This study aimed to determine the contamination level of Giardia cysts and Ascaris eggs for crops designated for human consumption. Collected crops in irrigated fields were turnip, marrow, squash, potatoes, pepper and eggplant. Field trials were also carried out on four crops, coriander, carrots, mint and radish, using three water types for irrigation, i.e. raw waste water, treated waste water (sedimentation and 16 days retention) and fresh water. Giardia cysts were detected at a level of 5.1 cysts/kg in potatoes, while Ascaris eggs were observed in numbers varying between 0.18 eggs/kg in potatoes and 0.27 eggs/kg in turnip. Field trials confirmed that irrigation of crops by raw waste water leads to contamination. Giardia and Ascaris were isolated in coriander at concentrations of 254 cysts/kg and 2.7 eggs/kg, respectively; mint was also highly contaminated with numbers reaching 96 cysts/kg and 4.63 eggs/kg. Carrots and radish were contaminated and respective numbers observed for Giardia were 155 and 59.1 cysts/kg; Ascaris was discovered in numbers of 0.7 and 1.64 eggs/kg, respectively. However, cultures irrigated with treated waste water and fresh water were free from contamination. Cysts and eggs on coriander persisted for a maximum of 8 days.

Potential of closed water systems on dairy farms

A more sustainable water management on dairy farms is necessary because of rising tap water production costs and exhaustion of groundwater resources in an increasing number of areas. Alternative water sources like rain water collected from roofs and yards and effluents from on-site wastewater treatment should be considered. The objective of this paper is to discuss options for closed water systems on dairy farms. Animal drinking and cleaning of milking equipment are major water demands on dairy farms. In some regions large volumes are needed for grassland irrigation or manure flushing. Treatment of dairy farm wastewater in constructed wetland systems seems to produce good quality effluents. The most plausible options for closed water systems on dairy farms are the collection and use of rain water and treatment and reuse of wastewater for irrigation, manure flushing and animal drinking water. Whether effluents are safe to be used as animal drinking water should be subject to further research.