Analysis of treated wastewater reuse potential for irrigation in Sicily

In Mediterranean countries, water shortage is becoming a problem of high concern affecting the local economy, mostly based on agriculture. The problem is not only the scarcity of water in terms of average per capita, but the high cost to make water available at the right place, at the right time with the required quality. In these cases, an integrated approach for water resources management including wastewater is required. The management should also include treated wastewater (TWW) reclamation and reuse, especially for agricultural irrigation. In Italy, TWW reuse is regulated by a quite restrictive approach (Ministry Decree, M.D. 185/03), especially for some chemical compounds and microbiological parameters. The aim of the paper is the evaluation of TWW reuse potential in Sicily. A Geographic Information System (GIS) was built at regional level to quantify and locate the available TWW volumes. In particular, the characteristics of wastewater treatment plants (WWTPs) were integrated, through the GIS, with data on irrigation district areas. Moreover, in order to evaluate the Italian approach for reuse practice in agriculture, the water quality of different TWW effluents was analysed on the basis of both the Italian standards and the WHO guidelines.     

污水灌溉对土壤质量的影响研究进展

综述了近年来国内外对污水灌溉对土壤质量影响的研究,并针对我国污水灌溉存在的问题,对污水灌溉今后的发展进行了展望。     

Effects of aquifer thermal energy storage on groundwater quality and the consequences for drinking water production: a case study from The Netherlands

We used data from an aquifer thermal energy storage (ATES) system located 570 m from a public water supply well field in the south of The Netherlands to investigate the relation between production of renewable energy with an ATES system and the production of drinking water. The data show that the groundwater circulation by the ATES system can impact chemical groundwater quality by introducing shallow groundwater with a different chemical composition at greater depth. However, the observed concentration changes are sufficiently small to keep groundwater suitable for drinking water production. Microbiological results showed that the ATES system introduced faecal bacteria in the groundwater and stimulated the growth of heterotrophic micro-organisms. At the studied site this forms no hygienic risk because of the long distance between the ATES wells and the public supply well field A further degradation of either chemical or microbiological groundwater quality however may necessitate additional water treatment which raises the energy requirements. The additional energy requirements for drinking water treatment may be up the same order of magnitude as the harvested energy by the ATES system.     

污灌区农田生态环境质量模糊综合评价

将"自然-社会-经济"的复合系统作为评价对象,采用层次分析法为生态环境建立评价指标体系,更客观更科学地描述污灌区生态环境质量.采用模糊综合指数法,计算分析了开封市污灌区生态环境质量、污水灌溉引起的土壤污染程度以及土壤污染对当地社会经济可持续发展的影响.最后,提出了污灌区土壤污染生态修复治理措施及污灌区生态环境可持续发展对策.     

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.     

Municipal wastewater treatment with pond-constructed wetland system: a case study.

The performance of a pond-constructed wetland system in the treatment of municipal wastewater in Kiaochow city was studied; and comparison with oxidation ponds system was conducted. In the post-constructed wetland, the removal of COD, TN and TP is 24%, 58.5% and 24.8% respectively. The treated effluent from the constructed wetland can meet the Chinese National Agricultural and Irrigation Standard. The comparison between pond-constructed wetland system and oxidation pond system shows that total nitrogen removal in a constructed wetland is better than that in an oxidation pond and the TP removal is inferior. A possible reason is the low dissolved oxygen concentration in the wetland. Constructed wetlands can restrain the growth of algae effectively, and can produce obvious ecological and economical benefits.     

Role of irrigation and wastewater reuse: comparison of subsurface irrigation and furrow irrigation.

Two different irrigation systems, subsurface drip irrigation and furrow irrigation, are tested to investigate the level of viral contamination and survival when tertiary effluent is used in arid and semi-arid regions. The effluent was injected with bacteriophages of PRD1 and MS2. A greater number of PRD1 and MS2 were recovered from the lettuce in the subsurface drip-irrigated plots as compared to those in the furrow-irrigated plots. Shallow drip tape installation and preferential water paths through cracks on the soil surface appeared to be the main causes of high viral contamination in subsurface drip irrigation plots, which led to the direct contact of the lettuce stems with the irrigation water which penetrated the soil surface. The water use efficiency of the subsurface drip irrigation system was higher than that of the furrow irrigation system. Thus, subsurface drip irrigation is an efficient irrigation method for vegetable crops in arid and semi-arid regions if viral contamination can be reduced. Deeper installation of drip tapes, frequent irrigations, and timely harvests based on cumulative heat units may further reduce health risks by ensuring viral die-off under various field conditions.     

Gas pockets in a wastewater rising main: a case study

This paper presents a case study of an existing wastewater rising main (WWRM) in which an extreme transient event produced by simultaneous power failure of the pumps caused the rupture of a 1.2 m (48 in) prestressed concrete cylinder pipe (PCCP), causing an important leakage of sewage. The event and the methodology followed in order to validate the diagnostics of the failure are described. The detail study included in situ observation of the system, experimental investigation in a setup, hydraulic analysis, as well as details of the structural strength of the WWRM. After the extensive investigation and several simulations of fluid transients for different scenarios and flow conditions, it was found that stationary small gas pockets accumulated at high points of the WWRM were identified as the principal contributory factor of the failure. This case study serves as clear warning of the consequences of operating a WWRM with gas pockets at its high points.     

UV disinfection of wastewater effluents for unrestricted irrigation.

Wastewater reuse in arid regions is important for the production of a water resource to be utilised for non-potable purposes and to prevent the environmental transmission of disease-causing agents. This study was conducted to evaluate the effect of water quality on the comparative disinfection efficiency of viruses, bacteria and spores by UV irradiation. Furthermore, the microbial quality of effluent produced by coagulation, high rate filtration (HRF) and either UV irradiation or chlorination was determined. Using low pressure collimated beam, a UV dose of 80 mWs/cm2 was needed to achieve a 3-log10 inactivation of either rotavirus SA-11 or coliphage MS2, whereas over 5-log10 inactivation of E. coli was reached with a dose of only 20 mWs/cm2. B. subtilis inactivation was found to be linear up to a dose of 40 mWs/cm2 and then a tailing up to a UV dose of 120 mWs/cm2 was observed. It is worth noting that effluent turbidity of < 5 NTU did not influence the inactivation efficiency of UV irradiation. Operation of a pilot plant to treat secondary effluent by coagulation, HRF and UV disinfection at a UV dose of 80 mWs/cm2 resulted in the production of high quality effluent in compliance with the Israel standards for unrestricted irrigation (< 10 CFU/100 mL faecal coliform and turbidity of < 5 NTU). Sulphite reducing clostridia (SRC) were found to be more resistant than coliphages and F coliform for UV irradiation. The results of this study indicated that UV disinfection is suitable for the production of effluents for unrestricted irrigation of food crops.     

Reuse of industrial wastewater for the irrigation of ornamental plants.

This paper describes the results of experimental activities carried out for verifying the possibility of reusing reclaimed wastewater originated from textile (70%) and domestic (30%) activities for the irrigation of container-grown ornamental shrubs. Aspects that concern the refinery treatment of reclaimed wastewater and the effect of irrigation on some ornamental plant species were investigated. An experimental site consisting of a refinery treatment pilot plant (filtration and disinfection) and an agronomic experimental area was set-up. The combined treatment of PAA and UV, used for the disinfection, showed to be very effective for inactivation of E. coli with most of PAA and UV dose combinations able to assure total inactivation. The plants (Buxus, Photinia, Pistacia and Viburnum), sprinkle and drip irrigated with well water (WW), reclaimed wastewater (RW) and a water mixed (MW) between reclaimed wastewater and well water (1:1 by vol), showed interesting results. A similar growth among different treatments was achieved for Buxus and Pistacia, while Viburnum and Photinia plants showed a higher sensibility to MW and RW. Photinia, in particular, turned out to be very sensitive to sprinkle irrigation with the reclaimed water, while the drip irrigation had no such bad effects, as reported in previous works.     

E. coli transport in soil columns: implications for reuse of treated wastewater in irrigation.

Reuse of treated wastewater in irrigation is gaining recognition as a vital element in the water resources management plan of developing countries, especially those situated in arid and semi-arid regions. An understanding of the transport of residual pollutants from treated wastewater, such as bacteria, in soil as a result of irrigation is critical to assessing health risks and the possible contamination of limited groundwater resources. In this work, retention of E. coli is evaluated for a soil that is irrigated by treated wastewater for growth of non-food crops near Egypt's Red Sea coast. In particular, the effects of soil organic fraction (SOF) and hydraulic loading rate (HLR) were investigated in laboratory soil columns. The matrix of experiments included three HLRs and three SOFs. The retention of bacteria by adsorption was observed at HLRs of 5 and 13 cm/h, with the magnitude of the adsorption increasing proportionally to the SOF. The impact of SOF was greater for the lower HLR. At the lowest HLR investigated (5 cm/h), filtration was also observed for the two higher SOFs (0.674 and 2.04 per cent). At a high HLR (66 cm/h) simulating flood irrigation, retention of bacteria was minimal regardless of the SOF. Since the bacterial solution is applied to a dry soil column to simulate field conditions, E. coli breakthrough after two pore volumes of throughput (vs. one) provided a meaningful comparison of bacterial retention as a function of HLR and SOF.     

Impacts of agricultural policy on irrigation water demand: a case study of Saudi Arabia

Saudi Arabia's groundwater resources have been heavily over-exploited to achieve food self-sufficiency. The country enacted a new agricultural policy that discourages the cultivation of wheat and encourages that of vegetables and fruits. This has produced significant reductions in irrigation water demand as well as food self-sufficiency. This paper reviews the performance of the Saudi agricultural sector and presents four scenarios forecasting the new policy's long-term impacts on the use of water for agriculture. The findings show that the new policy does not support sustainable utilization of groundwater resources. Additional policy modifications are needed to optimize the combination of import and domestic production of agricultural products based on a sustainable water utilization strategy.     

深圳特区城市中水道系统规划研究

在实现污水再生利用的诸多方式之中,城市中水道是实现污水回用的适宜工程系统,是城市供排水走向水健康循环利用的桥梁。介绍了深圳特区城市中水道系统规划,规划特区中水道供水能力2005年达22万m3/d,2010年为49万m3/d。届时将大幅度缓解水资源不足的压力,显著改善特区水环境。     

Agronomic aspects and environmental impact of reusing marginal water in irrigation: a case study from Egypt.

Egypt produces approximately 2.4 million m3 of secondary treated wastewater (TWW) annually, used for irrigation directly or indirectly by blending with agricultural drainage water (BDW). The annual re-use of (BDW) is approximately 4 million m3. The safe and efficient use of marginal water (BDW and TWW) is a core objective of this study which has been operating from 1997 to date. After six growing seasons the main results can be summarized as follows: MAXIMIZING CROP PRODUCTION: TWW can be used for high production of oil crops (canola, soybean sunflower or maize) compared to fresh water, while BDW can be used for high production of tolerant crops (cotton and sugar beet). CROP QUALITY: using marginal water increases the concentration of elements (Pb, B, Ni, Co) in all crops but these elements were under critical levels (there were no toxicity hazards). It is better to use alternative irrigation with fresh water under a drip irrigation system to maximise crop production and minimise the adverse effects of such water in field crops quality. SOIL POLLUTION AND SALINITY BUILD UP: A drip irrigation system under alternative irrigation by fresh with TWW or BDW reduces salinity build up risks and the levels of elements (Pb, B, Ni, Co) in soil compared to re-use marginal water. SOIL PATHOGENS: Using marginal water slightly contaminated the soil with total faecal coliform (TFC), mites, shigella and salmonella. PLANT ANATOMY: No great changes in anatomical disturbance where induced in different structures of plants which were reduced at maturity stage. PRIMARY GUIDELINES FOR RE-USING MARGINAL WATER: From obtained results it can be recommended to use marginal water with salinity content ranged between 1.1 to 3.64dS/m, and elemental contents (Pb 3.0-3.51 ppm), (B 0.05-1.67 ppm), (Co 0.04-0.07 ppm), (Ni 0.08-0.15 ppm) for safe (field, vegetable and medicinal) crops production. REUSE BIO SOLIDS FOR CROP PRODUCTION: Sewage sludge produced from treated wastewater can be safely used by mixing with rice straw (1:1 w/w) for economic crop production and saving mineral fertilisers. GENERAL CONCLUSION: In the North Nile Delta, marginal water (especially BDW) can be safely used without significant negative impact on the environment, but there is a need for multi-disciplinary, long-term research to investigate irrigation with marginal water in terms of the environment, public health and agricultural productivity.     

Subsurface constructed wetlands for wastewater treatment and reuse in agriculture: five years of experiences in Sicily, Italy.

The paper reports the results of an investigation on a H-SSF constructed wetland for tertiary treatment in a small community located in eastern Sicily, Italy. The system is designed to reuse wastewater for the irrigation of olive orchards covering about 150 hectares. From March 2001 to September 2005, wastewater samples were collected and the following chemical-physical parameters were determined according to Standard Methods: temperature, pH, EC, DO, TSS (105degrees C), BOD5, COD, TN, TP. The following microbiological parameters were also evaluated: total coliforms, faecal coliforms, Escherichia coli, faecal streptococci, Salmonella, helminth eggs. Mean removal efficiencies ranged from 77 to 92% (TSS), 37 to 72% (BOD5), 51 to 79% (COD), 97 to 99.5% (E. coli). Removal efficiency of Salmonella and helminth eggs was always 100% in all samples; however, only 150% of total samples matched the limit of E. coli (< 50 CFU/100 mL) fixed by Italian legislation for wastewater reuse.     

Evaluating the application of a decision support system in identifying adequate wastewater treatment for small communities. A case study: the Fluvia River Basin.

The identification of adequate wastewater treatment for small communities is a complex problem since it demands a combination of data from different sources, such as aspects of the community and landscape, the receiving environment and the available wastewater treatment technologies. The Catalan Water Agency (Agència Catalana de l'Aigua) considered using an EDSS (Environmental Decision Support System) as a tool to help water managers select the most adequate treatment for the urban wastewater of nearly 3,500 small communities in Catalonia (Spain). From that moment, EDSS was applied to all the river basins in Catalonia. In this paper the authors present the results obtained for the 76 small communities located in one of these river basins: the Fluvia River Basin. The characteristics of the community used in the reasoning process of the EDSS, the list of selected wastewater treatment alternatives, the technical environmental justification for the selected treatments and the reasons for discarding, favouring or disadvantaging them are presented. Finally, some results for the Fluvia River Basin are compared with those obtained in other Catalan river basins with different characteristics in order to evaluate which are the significant features in identifying adequate wastewater treatments.     

Monitoring and evaluation of Nigeria's irrigation systems: The case of the Bakolori irrigation project

One of the major banes of water resources development projects in Nigeria is lack of effective monitoring and evaluation. This apparent neglect has resulted in the inability to complete projects within the stipulated period, escalation of costs, poor design and construction works, and inevitably poor performance. This article reports the result of a diagnostic survey of the Bakolori Irrigation Project (BIP), one of the most controversial schemes in Nigeria. It is suggested that project monitoring and evaluation should be made compulsory on all irrigation projects in Nigeria, if they are to make any meaningful beneficial impact on the rural development process.     

水平畦灌技术参数对灌水质量及春小麦产量影响的试验研究

通过春小麦水平畦灌试验,研究了石羊河流域不同灌水技术参数组合对灌水质量和春小麦产量的影响。结果表明,在试验条件下,随着畦田纵坡的增大,灌水质量和春小麦产量降低;单宽流量越大,灌水效率越高,而单宽流量过大,有可能对田面造成冲刷,造成灌水均匀度降低;随着畦长的增大,灌水效率减小,灌水均匀度也减小。为此,提出了适合于石羊河流域金塔灌区水平畦灌的技术参数。     

Viability of increasing the tariff of freshwater for irrigation as a tool to stimulate wastewater reuse in the MENA region.

Despite water scarcity and high agricultural water demand in the Middle East and North Africa region, substantial proportions of treated wastewater are discharged into the environment and seas without proper utilization. All countries of the region, low pricing of reclaimed wastewater is a common tool to make reuse attractive. However, low pricing of reclaimed wastewater is ineffectual due to farmers' access to freshwater for irrigation at low tariff. Therefore, increasing the prices of freshwater in such a way that does not jeopardize feasibility of agriculture would promote irrigation with reclaimed wastewater even at increased prices. On one hand, it increases the gap between the price of freshwater and that of reclaimed wastewater, making the later more attractive. On the other hand, it would be used as a financial resource for funding the investment costs of the infrastructure needed for conveyance and distribution of reclaimed wastewater. This paper studies the viability of increasing the prices of freshwater and reclaimed wastewater. The results show that irrigation with reclaimed wastewater even for restricted irrigation can be as profitable as, and sometimes better than, freshwater irrigation. Some of the permitted crops such as fruit trees can be more profitable than vegetables. Thus, it appears that the level of knowledge farmers and others on the benefits of reclaimed wastewater is still limited.     

Reuse of wastewater effluent for irrigation in severely arid regions

Al‐Hassa oasis, with an estimated population of 750000, is one of the main agricultural areas in Saudi Arabia. The estimated present agricultural water consumption in the oasis is almost 419 × 10⁶ m³ per year and the water is mainly supplied from the aquifer systems in the oasis. The climate is severely arid and the groundwater resources are limited. A deficiency in irrigation water supplies would occur in the oasis, especially during the summer season, without the reuse of wastewater effluent. Alternative schemes were developed on the basis of climatic, irrigation method, crop, health and economic considerations for the potential reuse of wastewater effluent for irrigation purposes. The schemes suggested different alternatives for reuse of the untreated effluent or with various types of additional treatments needed to render the water free of health hazards and suitable for agricultural use. An expected average wastewqter effluent of about 32.2 × 10⁶ m³/year will be available for irrigation purposes. This will result in minimizing the mining of groundwater and in conserving the water resources in Al‐Hassa oasis.