Fertigation plays an important role in the so-called circular economy since it relies on the reuse of water and nutrients; therefore, this method is fundamental for production in areas with scarce resources. This study aimed to evaluate the effects of fertigation of soil plots with sewage on soil attributes, germination of seeds, and growth of bean and corn.

Due to the low concentrations of macronutrients in the sewage, the applied dose was calculated based on the water deficit. Three plots cultivated with maize and three plots cultivated with beans were fertigated, while the same number of plots received irrigation and mineral fertilization in amounts equivalent to the dose of nitrogen administered in the sewage for comparison.

There was an increase in the cation exchange capacity (74.6%), nitrogen (10.4%), available phosphorus (190.5%), and organic matter (44.9%) contents in the fertigated soil compared to those in the soil of the plots that received chemical fertilization, resulting in greater germination and corn and bean growth. Analyses indicated that the coliform count in beans is below the detection limit of the technique used.

Based on the results obtained, there are indications that fertigation can provide improvements in soil attributes at values higher than those provided by chemical fertilization, reducing the need to apply these macronutrients and irrigation water to the soil. Furthermore, fertigation can be sanitary and safe, since the count of microorganisms in the beans was not higher than that recommended by the World Health Organization (WHO).

Reusing organic wastes such as sewage sludge is a good way of returning organic matter and nutrients into soil. However, the likelihood of heavy metal accumulation in soil and the subsequent contamination of human and animal food chains should be determined before any attempt is made to reuse organic wastes. The purpose of this greenhouse study was to investigate the impact of sewage sludge from the effluent of Isfahan Polyacryl Corp. on yield and shoot cadmium concentrations in corn as compared to the animal manure and mineral salt of cadmium. A completely randomized design with three treatments (cow manure, sewage sludge at 25 Mg/ha, and 5 and 10 mg/kg Cd as CdCl2) was used. Corn seedlings were harvested 60 days after planting and Cd concentration was measured in the shoot. Application of animal manure and sewage sludge significantly increased corn biomass. Cadmium increment, in both organic and mineral salt treatments, significantly increased cadmium concentration in the corn shoot. The plant cadmium concentration in the soil treated with industrial sewage sludge and CdCl2 were significantly higher than that treated with animal manure.

The reuse of reclaimed wastewater has been increasing over the past decade, especially in arid and semiarid regions where reclaimed wastewater is used to conserve valuable potable water supplies. Careful consideration must be given to the hazards to health that may arise from the reuse of sewage, the hazards to health can be reduced by the treatment of sewage before use in agriculture. Conventional wastewater treatment processes such as activated sludge are generally very effective at removing nematodes eggs by sedimentation.WHO guidelines stated that the wastewater treatment system should produce an effluent with less or equal to one intestinal nematode egg per litre and less or equal to 1000 faecal coliforms per 100 ml to permit its reuse in unrestricted irrigation.In this research the efficiency of Shoosh Wastewater Treatment Plant (SWTP) in removal of nematods Eggs was investigatigated for eleven months during the years of 2000-2001. SWTP operates on activated sludge process and the grab samples of raw wastewater and effluent of system were taken daily every morning. Intestinal nematode eggs were counted according to standard method (APHA, 1995).The mean concentration of nematode eggs namely, Ascaris lumbricoides, Trichuris churia, Enterobios vermicularis and Hook worms were 4.4, 0.5, 0.9 and 1.1 eggs per litre, in raw sewage respectively. The concentration of total nematode eggs in raw sewage was 6.8 eggs per litre. The results of research showed that no nematode eggs were present in the final effluent throughout the period. Thus the effluent quality suitable for reuse in unrestricted irrigation. The results showed that activated sludge processes may remove 100 percent of influent intestinal nematode eggs.

Sanitary disposal of sewage and safe reuse of effluents are of utmost importance. The present study was conducted to evaluate the efficacy of Ekbatan sewage treatment plant in 2000-01. This cross sectional study was conducted between 1999 till 2000 in Ekbatan sewage treatment plant. Samples of inflow and effluent were taken weekly and TSS, BOD, COD, and PH were checked. Removal percentage of TSS, BOD, and COD were 96, 94, and 92%, respectively. The mean concentration of TSS, BOD, and COD of effluent were 8, 12.6, and 31.6 mg/l, respectively, that was within the normal range offered by EPA standard. Ekbatan sewage treatment plant has the ability of removal pollutants from the effluent. Its effluent could be safely discharged to receiving water bodies or used for agricultural means.

The aim of this study was to examine the possibility of reuse of wastewater of Shahrekordʼs sewage treatment plant for agriculture and determine the restrictions of use of wastewater in drip irrigation system in terms of influence on emitter clogging potential.
For this purpose, some of physical, chemical and biological parameters of wastewater quality of Shahrekordʼs sewage treatment plant, in April-September 2015, were measured on a monthly basis and then compared with the Iranian Environmental Protection Organization standards, World Health Organization standards (WHO), World Food and agricultural organization (FAO) and the standard of water quality classification according to the emitter clogging potential.
According to the results of water quality, the average amount of fecal and total coliforms in wastewater during the study, were 6416.8 and 16966.7 (MPN/100ml), respectively; that was outside of the recommended permissible range by the Iranian environmental protection organization standards for wastewater use in agriculture, so more chlorination is necessary, before wastewater discharge. In addition, based on the average value of microbiological parameters, fecal coliform and the number of intestinal nematodes (0 N/100ml) and according to World Health Organization standards, the use of wastewater for irrigation of plants that can be eaten raw, is not possible. Also according to FAO standard, wastewater application in terms of average amount of bicarbonate concentration in this period (4.64 me/L), had low to moderate limitation for crops. restriction Degree on use of wastewater in drip irrigation system in terms of average amount of total coliform count, level of pH (7.65) and water hardness (251.1 mg/L), was Moderate, and in the terms of average value of concentration of dissolved solids (405.5 mg/L), the concentration of suspended solids (35.2 mg/L), electrical conductivity (0.66 dS/m), iron (0.024 mg/L) and manganese (0.013 mg/L), was low. In addition, according to the negative value of langelier saturation index during the study period (-1.03), the possibility of sediment in the water, there weren’t.
According to the low potential of emitter clogging duo to physical and chemical agents, biological agents, considered as the main cause of emitter clogging when wastewater of Shahr-e kordʼs sewage treatment plant, use in drip irrigation systems. Thus, drip irrigation systems can be used in program of reuse of wastewater of sewage treatment plant in Shahr-e kord for irrigation of cereal and industrial crops resistant to high concentrations of bicarbonate and with consideration the use of managements such use of appropriate filter, acidification, flushing of laterals and especially chlorination of the irrigation system.

The disposal of sewage with acceptable qualitative characteristics to different acceptor resources is an environmental issue that today's societies face (with). Using the MatLab software, a neural network model, and an adaptive neuro-fuzzy inference system (ANFIS), this study has predicted the qualitative parameters (COD, BOD5, and TSS of the wastewater, along with TS, VS, and SOUR of the sludge) for the south Tehran sewage treatment plant and finally chosen the best models by validating the model and using the defined criteria. Moreover, using these developed models and comparing their results with the available standard values provides a suitable classification to reuse the wastewater and sludge of the south Tehran wastewater treatment plant. The results indicated acceptable errors of both systems, the adaptive neuro-fuzzy inference system and the artificial neural network, in predicting the qualitative characteristics of the sludge and wastewater of the south Tehran sewage treatment plant and the priority of the adaptive neuro-fuzzy inference system over the artificial neural network in estimating the quality of the treated wastewater and sludge.

In recent years, excessive usage of surface and underground water resources has exerted great stress on Iran's water resources. A survey of water use trends in the past years and forecasts of water needs in the coming years, makes undesirable  perspective for the imbalance between water demand and resources in the near future. Planning for the exploration and use of unconventional water resources, such as gray water and sullage reuse, will greatly help to balance water shortage. In this research, sewage of swimming pools has been investigated because it is a type of urban sewage that has high technical, economic and environmental potential for implementation of urban sullage recycling project. A case study was carried out on 10 public swimming pools in Tehran to determine the volume and 7 pools for qualitative investigation on sewage of different parts of swimming pools. The results indicate that pools have a high quality and high volume wastewater that cause conceivable potential for recycling. For example, the average COD of the tested samples was 153 ppm and the maximum was 246 ppm, which is equivalent to organic load of weak urban wastewater. This wastewater also meets the standards of landscape irrigation in most of parameters, and in the other parameters such as organic load of some samples has a small variance from these standards, which could be met with a simple treatment unit like a depth filtration and an activated carbon. In addition, an average of 120 cubic meters of sullage per day is generated in each aquatic center complex, which is more than the production of gray water in a 700 people capacity residential complex. Reuse of this sullage, in addition to reducing transportation costs and load of centralized treatment plants, will reduce the pressure on water resources of our country by supplying water for non-potable purposes such as irrigation of landscaping.

Environmental problems suffering from fossil fuels,trying to find alternative human energy supply and the presence of huge amount of energy in wastewater, considers sewage as an economicallyviableand environmentally-friendly optionsource of energy.Also, wastewater treatment in a localized manner consults reuse of water in the water cycle, but a recovery of wastewater and the return of water to the water cycle requires lots of energy.Using microbial fuel cells as a solution to this path is considerable andwastewater treatment, using these types of fuel cells, would make it possible to generate the energy required by the system.

Municipal wastewaters are the most generally available source of wastewater that have been longly used specially for agricultural irrigation (sewage farms) in order to conserve fresh water. Although this practice often costs less than other forms of water reuse because it requires less additional treatment processes but it may cause excess risks when environmental considerations are not taken into account. In other words, agricultural reuse may degrade the quality of soil and water if required considerations not applied. Therefore, a sound program for selection of suitable site is extremely important. In this regard, the more important factors that are now essential to consider are as follow:Proposed or existing land use, site features including topography, proximity to water bodies, level of groundwater, soil permeability, vegetation, public access and proximity to dwellings. Furthermore, water balance for the site, storage requirements, nutrient balance assessment for the site and installation and maintenance requirements for such systems are another important factors required to be considered. A brief discussion of each are present in the paper.

Background and Direct application of sewage sludge in agriculture is limited due to the presence of pathogens¡ improper fermentation of organic waste and heavy metals in the sludge. Co-composting of sewage sludge and other waste is a method for safe and healthy disposal to reuse sewage sludge. This study investigated the possibility of producing compost from sewage sludge and pistachio hull waste.
Material and A cross-sectional study was conducted in the winter of 2014 at the Environmental Health Engineering Research Center affiliated to Kerman University of Medical Sciences. First¡ a cylindrical reactor was made which was 30liters in volume¡ 30cmdiameter in dimensions¡ 45cm depth¡ and wall thickness of 6 mm. Pistachio hull waste with sewage sludge was mixed in a ratio of 1 to 4 and C/N ratio of 25. Reactor started with aeration rate of 5 liters per minute. The reactor content was mixed every five days¡ and the resulting compost samples were measured for moisture content¡ pH¡ electrical conductivity¡ organic carbon¡ total nitrogen¡ phosphorus¡ potassium¡ cadmium¡ and lead.
After 30 days from the start of composting process¡ the carbon to nitrogen ratio decreased to 16.5. During the composting process¡ pH increased but the amounts of electrical conductivity¡ total nitrogen¡ organic carbon¡ phosphorus¡ potassium¡ lead¡ and cadmium decreased. The maximum temperature reached 63ºc.
The properties of the produced compost including temperature¡ pH¡ electrical conductivity¡ moisture ratio¡ C/N¡P¡ K¡ and heavy metals were in category 1 and 2 of the standard compost of Iran.