Seasonal variation effect on water quality and sediments criteria and its influence on soil pollution: Fayoum Governorate, Egypt

Abstract

Background

Irrigation with low-quality water without considering the acceptable levels negatively impacts not only humans, but also extends to the whole surrounding ecosystem. The current research is a comprehensive-integrated appraisal of the irrigation water quality gathered from El-Batts drain in Fayoum Governorate, from September 2021 to June 2022, together with the drain sediments and the soils adjacent to it. The characteristics (physical, chemical and biological), and the risk fate of some heavy metals (As, B, Cr, Cu, Zn, Cd, Pb, Ni, Fe and Mn) were measured. Moreover, the risks of the studied pollutants were assessed using many indices: irrigation water quality index (IWQI), contamination factor (Cf), degree of contamination (Cd), Salinity indices and Zn equivalent (ZE). Additionally, kinetic studies of the inorganic pollutants were evaluated to determine their availability and impact on the surrounding environment.

Results

Data from IQWI showed that water in all five sites was assumed to be very bad and unsuitable for usage with a general average (14.62 and 25.35) in all four seasons. ZE exceeds the critical level of 250, which means there is a risk of soil contamination.

Conclusions

The elevated levels of heavy metals, microbial enzymes, pathogenic fecal coliform and Salmonella reflect bad and direct risk of dealing with such water in irrigation and its effect on the soil ecosystem and the growing crops. Most of the tested parameters exceeded the acceptable levels of the Egyptian Governmental Law Guidelines, WHO and FAO, which may threaten aquatic life. Best managements practices and remediation techniques should be applied to minimize the hazards in such waters.

Background

In the last decades water has emerged as the major environmental concern of the twenty-first century. After global warming, many parts of the world especially in arid and semi-arid regions are currently facing water shortages, while other parts have to face severe water pollution.

Recently, Egypt has experienced a severe water shortage. The per capita water share has significantly decreased to less than 1000 m³/year, as the “water poverty limit”. By the year 2025, it is anticipated that this value will be dropped to 500 m³/capita [1, 2]. In addition, the deterioration of water quality is a major issue affecting Egypt’s health and water security. Recently, there has been a widespread concern about the decreasing water grade/quality used for agricultural irrigation due to the growing population, the expansion of industrial/agricultural operations, and the global warming effect that could jeopardize the hydrological cycle. W. W. A. P. United Nations and UN-Water [3] provided an outline of Egypt's water management policies. Their findings indicate that, as the population grows, the amount of water used in 2025 will be less than in 2012.

In Fayoum Governorate, along the El-Batts drain, there are two origins of pollution, which negatively influence its quality and suitability for irrigation. The initial source is municipal wastewater, where a huge amount of wastewater is directly discharged into drainage channels forming a high peak of organic load [4,5,6]. The second origin is the agricultural runoff that emerges from agricultural activity [7]. The quality and the quantity characteristics of drainage received from agricultural regions are highly variable. The most crucial contaminants found in runoff from farming areas are crop residues, plant nutrients, sediments, inorganic salts and minerals, chemical pesticides, and fertilizers [8,9,10]. Application of this water in irrigation is the 2nd option, since the lack of available water [11]. Because of internal drainage, no water outflow other than evaporation [12, 13], meaning that all dissolved materials will remain and concentrate in the water or sediments of the ecosystem [14]. These conditions adversely influence the potentiality for the enduring development in the depression and additionally, increase the pressure on water and land resources in the governorate [15,16,17,18,19,20,21].

Abd-Elgawad et al. [22] collected 50 water samples to cover most water resources at Fayoum Governorate (Bahr Yousef, canals water before and after mixing with drainage water, drains water, Qaroun Lake, Wady El-Rayan and tap water). They concluded a precise long-term monitoring for salinity and heavy metals is essential for all water of Fayoum. Sources and risks of water containing heavy metals ecosystems order to face the increasing problems of water grade and contamination with heavy metals.

Our study comes one decade after the earlier mentioned study, with significant changes that took place in this ecosystem, the main objective of this work is: (1) to appraise the variations of the physiochemical characteristics, the contamination degree and the changes that arose in the grade of El-Batts drain water, sediments and adjacent farms through some important pollution indicators; (2) to ensure the suitability and the durability of this water for agricultural irrigation by investigating the seasonal variation and distribution of salts (chloride and sulfate salts), heavy metals (As, B, Cr, Cu, Zn, Cd, Pb, Ni, Fe, and Mn) and the existence of pathogenic microbes (Fecal coliform, E. coli and Salmonella); (3) study the current state of certain heavy metals represented by Ni, Cu, and Zn desorption and bioavailability in different selected cultivated soils in the areas under investigation through the kinetic study; (4) to give a clear and a detailed view of the study area to facilitate finding the appropriate methods of the best management practices and the suitable treatment technology.

Materials and methods

Environmental setting and elaboration of the study area

Fayoum located at Cairo southwest, lies a depression 50 m below mean sea level beyond the Nile, between latitudes 28° 55ʹ N and 29° 40' N and longitudes 29° 55ʹ E and 31° 5ʹ, respectively. The average annual rainfall in this region is 7.2 mm, and the climate is defined by hot, long, and arid summers and warm, short winters with little precipitation [23, 24].

Seasonally, the water’s temperature varies from roughly 14.5 to 33 °C. El-Batts (50.9 km) eastward and El-Wadi (48.5 km) westward are the two prime drains that service the irrigated farms in Fayoum, running parallel to the watering system. An annual volume of 390 to 450 million cubic meters was estimated for the drainage water. Nearly 338 × 10⁶ m³/year of water are received by El-Batts, and 84.5 × 10⁶ m³/year for El-Wadi drains [25,26,27,28,29].

Water sampling

Five fixed points along the drain canal were chosen to obtain low-quality water samples that are usually employed in irrigation. These samples were gathered to represent mixed drainage water consisting of sewage and industrial effluents (El-Batts drain), Fayoum governorate; during the period from September 2021 to June 2022, (September, January, March and June), representing the four seasons, i.e., autumn, winter, spring, and summer, and the samples were collected in three replicates. The selected sampling sites at Fayoum governorate (Fig. 1) were Ezbat Saad Abou Diab (Demo Area) (Site 1), Sila Area (Site 2), Ezbat Khalifa Younis (Al Rawdah Area) (Site 3) and Ezbat Al Hayyar (Qasr Rashwan Area) (Site 4), and Ezbat Farag Al Neweshey (Qarun Area) (Site 5).

Fig. 1

Map represents the location of water, sediments and soil samples at Fayoum Governorate

Water samples were held in closed sterile dark plastic water sample bottles with a 2-L polyethylene, they were kept at 4 °C in an ice box during transport. Also, the selected water samples were examined for their physiochemical properties and biological analysis purposes, to evaluate the appropriateness of this water source in irrigation.

Sediment sampling

Surface sediment (0–30 cm) samples were taken from the selected sites of irrigation using water samples along the El-Batts drain. Sediment samples were taken using a grab sampler, gathered in acid-washed polyethylene plastic bags, and stored at 4 °C. At room temperature, air-dried and sieved at a 2-mm, homogenized, digested using aqua regia [30], then analyzed for their inorganic pollutants contents represented by zinc (Zn), arsenic (As), nickel (Ni), lead (Pb), chromium (Cr), cadmium (Cd), iron (Fe), copper (Cu), manganese (Mn) and boron (B) concentrations, and microbial activities.

Soil sampling

To assess the adverse impacts of irrigating the soils with low-quality water on their properties, a composite surface (0–30 cm) and subsurface (30–60 cm) LQW-irrigated soil samples gathered from the agricultural farms of the same sites adjacent to the taken water samples (Fig. 1). The collected soils were air-dried, before being ground into fine particles with a 2 mm average size and analyzed for their chemical, physical and biological characters (microbial activities).

Physical and chemical evaluation

Water physiochemical characteristics were ascertained using the methods described in the American Public Health Association [31] as follows:

water temperature (°C) was measured using a digital thermometer, HANNA, model: Checktemp—HI98501. pH was measured using a glass electrode pH meter 3510, Jenway, UK. The electrical conductivity (EC) in dS m⁻¹ was measured using an electric conductivity meter (Thermo Electron Corporation, Orion 150A+, USA). Total solids (TS) were measured by evaporating a recognized volume of well-mixed water sample. Total dissolved solid (TDS) was determined by filtering a sample volume through a glass fiber filter (GF/C), and a known volume of filtrate was evaporated to dryness at 103–105 °C. Water turbidity was estimated by Turbidity meter Thermo Orion AQ 4500. Soluble cations and anions were measured in water samples: sodium and potassium (Na⁺, K⁺) using flame photometer Model JENWAY, PFP.7 UK, calcium and magnesium (Mg²⁺, Ca²⁺) by titration with (EDTA-Na⁺), chloride (Cl⁻) by titration with silver nitrate and water alkalinity represented in soluble carbonate and bicarbonate (CO₃²⁻, HCO₃⁻) was determined by titration with standardized sulfuric acid, using phenolphthalein and methyl orange indicators. Ammonia and nitrate were measured by the Kjeldahl method using the Gerhardt Vapodest 20S programmable distillation system. Total phosphorus was estimated by using a spectrophotometer, HACH, model DR5000, ammonium molybdate method. Total and available heavy metals in water and samples were determined using inductively coupled plasma emission spectrometry (ICP-ES) (PerkinElmer optima 3000, USA) instrument. Dissolved oxygen (mg/l) concentration was determined using a dissolve oxygen meter, HACH, model HQ3OD. Biological oxygen demand (BOD) was determined by using the 5-day incubation method by using BOD fast respirometry system model TS606/2 at 20 °C incubation in a thermostatic incubator chamber model WTW for 5 days. Chemical oxygen demand (COD) was performed calorimetrically using the potassium dichromate method. A strong chemical oxidant (potassium dichromate) in an acid medium. The blended solution was heated to oxidize organic carbon into carbon dioxide and water. It measures the consumed amount of dichromate in the breakdown of organic matter using a COD reactor (block heater operates at 150 ± 2 °C) and spectrophotometer HACH-model DR5000.

The criteria for evaluating the quality of water for agricultural irrigation purposes

The most crucial criteria used according to FAO [32,33,34] and used in this work are:

• pH of water, temperature, turbidity, and DO

• Salinity, alkalinity, sodicity, permeability, and infiltration rate hazards in terms of EC

• TDS

  $${\text{TDS }}\left( {{\text{mg}}/{\text{L}}} \right) = {\text{EC}}\left( {{\text{dS}}/{\text{m}}} \right) \times {\text{K,}}$$

  (1)

where k is the 640 if EC value < 5, or 800 if EC value > 5.

• Sodium adsorption ratio (SAR)

  $${\text{SAR}} = {{\left[ {{\text{Na}}^{ + } } \right]} \mathord{\left/ {\vphantom {{\left[ {{\text{Na}}^{ + } } \right]} {\left[ {\left( {{\text{Ca}}^{{2 + }} + {\text{Mg}}^{{2 + }} } \right)/2} \right]^{{1/2}} }}} \right. \kern-\nulldelimiterspace} {\left[ {\left( {{\text{Ca}}^{{2 + }} + {\text{Mg}}^{{2 + }} } \right)/2} \right]^{{1/2}} }}.$$

  (2)

• Soluble sodium percentage (SSP)

  $${\text{SSP}} = \left[ {\left( {{\text{Na}}^{ + } } \right)/\left( {{\text{Na}}^{ + } + {\text{K}}^{ + } + {\text{Ca}}^{{2 + }} +{\text{Mg}}^{{2 + }} } \right) \times 100} \right].$$

  (3)

• Residual sodium carbonates (RSC)

  $${\text{RSC}} = \left( {{\text{CO}}_{3}^{{2 - }} + {\text{HCO}}_{3}^{ - } } \right) - \left( {{\text{Ca}}^{{2 + }} + {\text{Mg}}^{{2 + }} } \right).$$

  (4)

• Residual sodium bicarbonate (RSBC)

  $${\text{RSBC}} = \left( {{\text{HCO}}_{3}^{ - } - {\text{Ca}}^{{2 + }} } \right).$$

  (5)

• Total hardness (TH)

  $${\text{TH}} = \left( {{\text{Ca}}^{{{2} + }} + {\text{Mg}}^{{{2} + }} } \right) \times {5}0.$$

  (6)

• Sodium-to-calcium activity ratio (SCAR)

  $${\text{SCAR}} = \left( {{\text{Na}}^{ + } /\surd {\text{ Ca}}^{{{2} + }} } \right).$$

  (7)

• Kelly ratio (KR)

  $${\text{KR}} = \left[ {\left( {{\text{Na}}^{ + } } \right)/\left( {{\text{Ca}}^{{{2} + }} + {\text{Mg}}^{{{2} + }} } \right)} \right].$$

  (8)

• Potential salinity (PS)/Doneen parameter

  $${\text{PS}} = \left[ {\left( {0.5 \times {\text{SO}}_{4}^{{2 - }} } \right) + {\text{Cl}}^{ - } } \right].$$

  (9)

• Specific ion toxicity (heavy metals)

• Organic matter indexed by BOD and COD

• Excessive nutrients: phosphates (PO₄³⁻), ammonia (NH₄), nitrate (NO₃⁻), chlorides (Cl⁻), and boron (B).

• Biological activity represented by fecal coliform bacteria, dehydrogenase, peroxidase and urease activities.

Soil physiochemical characters were determined as given in [35]. The measured parameters are:

Soil pH was measured using a glass electrode in soil paste. EC_e in dS m⁻¹ at 25 °C was determined in soil paste extract. Soluble cations and anions were determined in soil paste extracts. Total heavy metals were determined as given in [35]. Available heavy metals of soils were extracted by the ammonium bicarbonate-DPTA method as stated by [36]. Mechanical analysis was performed depending on the International Pipette Technique using sodium hexa-meta phosphate as a dispersing agent.

Soil quality index

Zn equivalent (ZE): ZE was expressed numerically for the toxicity levels of heavy metals, based on the following equation in ppm:

$$\left\{ {\left( {{\text{Zn conc}}. \times 1} \right) + \left( {{\text{Cu conc}}. \times 2} \right) + \left( {{\text{Ni conc}}. \times 8} \right)} \right\}.$$

(10)

A quality index of more than 250 indicates a risky circumstance, requiring remediation for enduring agricultural practices [35].

Sediment quality criterion indices

Sediment contamination with heavy metals was evaluated by:

• Contamination factor (Cf) and degree of contamination (Cd)

Cf and Cd were estimated depending on the mean concentrations of metals following the method [37]:

$${\text{C}}f = {\text{Ms}}/{\text{Mb,}}$$

(11)

$${\text{Cd}} = \mathop \sum \nolimits_{i = 0}^{n} \left( {{\text{C}}f} \right).$$

(12)

Sediment’s metal content (Ms), backdrop value of the same metal in average shale (Mb), and n is the number of the investigated metals.

Heavy metals kinetic studies

Kinetic experiments were done by batch technique [38, 39] on soil samples. Two-gram portions of soil were placed in a falcon plastic tube, and about 25 ml of the ammonium bicarbonate-DTPA was added. After vigorously shaking the solution, the extracts were collected at varied intervals fluctuating between 1 s, to 120 min or any time specified according to the stability of the ion(s) released from the studied soil samples at 25 °C. The concentrations of heavy metals were determined as given in [39] using ICP-ES.

Two kinetic models were applied to test data compliance of heavy metals release from studied contaminated soils:

• Elovich equation

$$q = (1/\beta )\ln (\alpha \beta ) + (1/\beta )\ln t,$$

(13)

where q is the amount of heavy metals desorbed at time t. α is the constant in ppm heavy metals min⁻¹. β is the constant in (ppm heavy metals)⁻¹. t is the time in minute.

• Modified Freundlich equation

  $$q = k_{d} t^{b\backslash } ,$$

  (14)

  where q is the amount of heavy metals desorbed in time t. k_d is the desorption rate coefficient in mg heavy metals kg⁻¹ soil min⁻¹. b\ is the constant in mg heavy metals kg⁻¹ soil.

Microbiological analysis of soil, sediment, and water samples

Microbiological analysis was performed to detect the presence of potentially pathogenic bacteria using serial dilution [40, 41], and direct plate count techniques. Total fecal bacteria were enumerated on MacConkey agar medium [42, 43] meanwhile, Salmonella count was detected on SS agar medium [43, 44]. 1 g of the soil sample was placed in 9 ml sterilized, distilled (SD) water that forms the first dilution. Subsequently, 1 ml of dilution was transferred to another tube containing 9 ml SD H₂O to prepare the second dilution. Serial dilution from 10¹ to 10⁶ prepared and plated in sterile Petri dishes to be poured and homogenized with the corresponding specific agar medium. The plates were incubated after solidifying at 37 °C for 48 h, and the existence of each type of bacteria was evaluated by direct count in CFU.

Dehydrogenase activity

Dehydrogenase activity was estimated according to the method referenced in [35]. The assay is based on using 2,3,5-triphenyl tetrazolium chloride (TTC) to replace atmospheric O₂ as H acceptor during the oxidation process. Five-gram portions of the soil or sediment (5 ml of water) sample was placed in a Stoppard 50 ml Erlenmeyer flask and mixed with 0.1% CaCO₃, 1.0 ml of 3% aqueous solution of TTC, and 1.0 ml of distilled water. The flask was stoppered and incubated at 30 °C for 24 h. The triphenyl formazan (TPF) produced was extracted with methanol and the contents of the flask were filtered. The soil was re-extracted and the filtrate made up to 50 ml volume with methanol. The intensity of the reddish color was measured using a spectrophotometer at a wavelength of 485 nm in a 1 cm cuvette with methanol as a blank.

The amount of TPF produced, with accordance to a calibration graph prepared from TPF standards, was calculated (formation of 1 mg formazan requires 150.35 pl of H₂). The dehydrogenase activity of the soil was expressed as (µl H₂/gm soil/24 h).

Peroxidase activity

Peroxidase activity was estimated according to the method referenced in [45, 46]. 167 µl sample was added to 533 µl K-phosphate buffer (pH 6) and 267 µl H₂O₂ (0.5) % with 533 µl pyrogallol and the assay volume was brought to 5 ml with DDH₂O (3500 µl), a blank sample was prepared by replacing the samples with phosphate buffer (167 µl) and the assay absorbance was measured calorimetrically at 420 nm after 3 min.

Urease activity

Urease enzyme was determined in the samples according to the method of [47], as follows:

In 50-ml measuring flasks, 10 ml of wastewater sample was transferred then 1.5 ml of toluene was added and incubated for 15 min. After that, 20 ml of citrate buffer pH (6.7) with 10 ml of 10% urea solution was added and the mixture was incubated for 3 h at 37 °C. After incubation, the samples were assayed to detect the free ammonium using the Nesslerization method for ammonia detection, calorimetrically at 420 nm.

Statistical analysis

Gained results were subjected to different statistical analyses, e.g., regression analysis, correlation analyses and standard division (SD) [48].

Results and discussion

Evaluation of El-Batts drain water

Water pH

Results in Table 1 showed that pH values ranged between 7.77 and 8.98 in different sites and all months studied with a significant decrease in March and also a significant increase in January. Normally, the irrigation water's pH varies from 6.5 to 8.4. pH beyond the range has the potential to cause an imbalance of nutrients or contain poisonous ions. The largest risk associated with an unusually high pH in water is how it affects irrigation water with high alkalinity levels, which can decrease the efficiency of the drainage system. The high pH of irrigation water is connected to elevated levels of Na⁺ and major anions (HCO₃⁻, CO₃²⁻, Cl⁻ and SO₄²⁻), this result could be noted in March with a significant increase in soluble Na reached about 29.78 meq/l and 33.25 meq/l in June at Site 5. Water pH does not have direct consequences on crops, except at extremes. The pH > 8.2 with excessive HCO₃ significantly affects crop yield and creates clogging problems. Moreover, high-pH water can produce salts to precipitate and can reduce the efficacy of pesticides [39].

Table 1 Chemical characteristics of low-quality water used in irrigation at different periods

Water salinity

Results in the same table demonstrated that salinity has been deemed the primary factor of agricultural irrigation water quality. Salinity determined ranged between 2.42 and 4.33 dS m⁻¹. Salinity affects both the crop yield and the soil's physical properties. High-salinity irrigation water has salinity hazards and is toxic to the plants. Results indicated that the maximum value was recorded in March and June and decreased in the autumn months (September). Significant increase in Na, Ca, and Mg compared to K which gave the minimum values in all sites and all months (Table 1). Sodium Na concentrations ranged between 11.46 and 33.25 meq/l with a significant increase in the summer months. In addition, Site 5 gave the highest values in all cations. Like Na Chloride Cl anion gave the highest values followed by SO₄ and HCO₃. Cl ranged between 10 and 26.33 meq/l, and between 5.17 and 13.89 meq/l for SO₄, while HCO₃ ranged between 3.73 and 10.40 meq/l, the lowest values of all anions. The salinity behavior of water in Table 2 is indicated by TS, TSS and TDS. TDS contains the anions and cations with changes in the color and characteristics of water. The highest values of TDS and TSS were observed in Site 5 (2771.20 and 516 mg/l), respectively, which exceed the acceptable levels of FAO (2000 mg/l for TDS and 100 mg/l for TSS).

Table 2 Some salinity criterion indices for irrigation water quality at different periods

The nutrients measured in the El-Batts drain showed a significant increase of total K⁺ ranging between 12.18 and 32.45 mg/l (Table 1), with other concentrations of phosphate P (0.39 and 10.46 mg/l) and Nitrogen in NH₄ (0.75 and 3.38 mg/l) and for NO₃ (5.78 and 15.79 mg/l), Site 5 was the elevated one. This result could be expected from receiving of different organic or inorganic wastes in the studied drain.

Water SAR

SAR represented in Table 2, ranged between 4.72 and 14.46 in all months and for all sites. SAR values varied between months in the same site. Site 2, for instance, the collected sample in March gave the highest value compared to the months studied where SAR value was 9.84 and 6.17 in January meaning severe danger and unsuitable water for irrigation. In other months, however, SAR values mean waters need to be treated especially in summer and spring seasons; it is pertinent to mention that the same pattern was noted in other sites. Results also showed that Site 5 gave the highest values compared to other sites with values reached to 13.44 and 14.46, the same trend was observed in SCAR which generally ranged between 4.13 and 13.44, and Site 5 had the highest values especially on June (13.44), meaning application of such waters will severely damage soil ecosystem. It ought to be mention that, high Na concentrations affect soil permeability and have a direct effect on the total salinity of water [1].

Potential salinity (PS)/Doneen parameter

Doneen parameter was used in rating the appropriateness of water for irrigation activities as it is considered an excellent indicator of such rating [34]. The value 5 is the critical level for using the water in irrigation or unsuitability to be applied to irrigation purpose [49]. Results in Table 2 indicated that the all estimated values of Doneen parameter surpassed 5 in all sites and in all months studied. The values ranged between 14.07 and 29.20 meaning unsuitability of this type of water to be used in irrigation and it should be mention that the highest value again was noted in Site 5 and in March.

Total hardness (TH)

Water hardness is a consequence of metallic divalent cations presence (Ca²⁺ and Mg²⁺). TH is classified [50] as soft (0–60 mg/l), moderately hard (60–120 mg/l), hard (120–180 mg/l) and very hard (> 180 mg/l).

Results in Table 2 indicated that the water samples gathered in all sites in different months ranged between hard and very hard waters (> 180). Numerically, in Site 1 TH ranged between 407.07 and 607.27 means that measured TH surpassed the acceptable level by five to ten times. A similar pattern was noted in sites 2 and 3. In sites 4 and 5, TH significantly increased to 729.06 and 919.25 in September and January and decreased to 477.14 and 493.38 in the other two months. In general, all the drainage water samples are very hard and unsuitable to be employed in irrigation, especially in sites 4 and 5.

Soluble sodium percent (SSP)

SSP less than or equal to 50% gives a good indication of water quality, while samples that are more than 50% are unsuitable for irrigation. Results in Table 2 showed a significant increase in SSP in some months. SSP values reached 73.28 and 62.36%; 69.16 and 66.25% in March and June for Site 1 and Site 2, respectively. SSP values increased to 71.41 and 72.32; 772.14 and 74.17%; and 73.65% for Site 3, Site 4 and Site 5, respectively, in the same months. In September and January, the parameter values were near the normal value, i.e., 50–60%.

Residual carbonate and residual bicarbonate (RSC and RSBC)

High residual carbonate or bicarbonate (RSC and RSBC) water content might be found in many arid and semi-arid regions, which are available for irrigation. A superfluous buildup of salts is frequently the consequence of their careless use for irrigation, and led to rapid salinization and sodification of the soil profile which adversely affected crop growth. Regarding the estimated values of RSBC cited in Table 2, all the values measured in June for different sites are higher than the permissible level (2.5), the critical value and reached from 4.40 to 5.37 in different sites. It is worth mentioning that the parameter values are almost in the normal range in other months. In addition, Site 5 in most cases showed high and unsuitable to be used in irrigation.

Kelly’s ratio (KR)/(KI) index

Abdel-Fattah et al. [34] introduced another index to evaluate the quality and categorize of water for irrigating purposes considering Na⁺ concentration against Ca²⁺ and Mg²⁺. A Kelly’s ratio over one indicates excessive Na in water. Therefore, water with a KR under one is appropriate for irrigation, while those over 1 are unsuitable.

Results of KR in Table 2 noted that in general, almost all values are higher than one. Again, the maximum values were observed in Site 5 with numerical values ranging between 0.92 to 3.14 meaning the unsuitability of this water for irrigation. Furthermore, KR values increased in water samples collected in June month compared to other collecting samples collected in other months, meanwhile, samples collected in September gave the lowest values.

Irrigation water quality index IWQI

IWQI is an important indicator of water use for agricultural irrigation and reflects the appropriateness of irrigation water for soil and plants. IWQI involved many important parameters that indicate the pollution degree of the contaminated water at its calculation such as water temperature, pH, TS, turbidity, DO, total PO₄, NO₃, BOD, and fecal coliforms [12, 34]. Results in Table 3 represent IWQI values estimated for El-Batts drain during the season at five different sites along the drain. Results emphasized that IWQIs at different sites are very bad and unsuitable for irrigation. IWQI values ranged between 14.94 to 19.16 for samples collected in September, 19.36 to 25.35 in January, 14.51 to 18.95 in March, and 14.62–17.62 in June. These result values showed very poor water types used in irrigation and it could be seen that unsuitability of such waters in irrigation. In all months, results showed that samples gathered from Site 5 gave the minimum values in IWQI; in addition, samples taken in winter (January) were the lowest values compared to samples taken in other months.

Table 3 Irrigation water quality index and quality rating for water samples collected from different sites at different months

Available and total heavy metals content in the studied water

The data of available and total forms of heavy metal contents in the investigated LQW are documented in Table 4. Total As and Cr reached 3.55 and 3.65 ppm in Site 5 while it was 0.16 and 0.50 ppm in Site 1, respectively. Results noted that the available B reached 1.28 and 1.33 ppm in Site 4 and Site 5, respectively, and increased to 2.19 in both sites. Results in Table 4 show high values of most of the water available heavy metals which exceed the permissible levels. Cr concentration values ranged from 0.01 and 2.80 ppm, the greatest value was recorded at Site 5, while Zn ranged between 0.27 and 4.03 ppm. The existence of both contaminants in irrigation water presumably originated from agricultural drainage water and the disposal of sewage effluents in the drain. Generally, all sites have a high content of heavy metals and exceed the acceptable levels except Pb. The highest concentration was detected at Site 5 and Site 1 was the lowest one.

Table 4 Total and available concentration of some heavy metals in irrigation water (ppm) at different studied locations at different periods

Dealing with the safe levels of heavy metals in irrigation water (Table 4), results indicated that the available and total concentrations of such pollutants in the tested waters greatly exceed the safe levels of irrigation water for both FAO and Egyptian Governmental Law 2013. Also, with the exception observed in the content of water available Cd, Pb, and Fe the levels of all other studied heavy metals exceeded the safe permissible level (Table 4). This result emphasized the unsuitability of these LQWs for irrigation. Stated differently, the use of such water in irrigation for a long time in the absence of percussions and remediation technique(s) would lead to severe adverse impacts, for the soil receiving such water [51].

Evaluation of sediments in different sites of El-Batts drain

The mean levels of all heavy metals were very high exceeding the acceptable levels of WHO, represented by Pb, Ni, Mn, Zn, B, As and Cr in the sediments.

Manganese (Mn) in sediments

The mean of Mn concentrations in sediments in different sites is recorded in Table 5. Mn was ranged from 237.5–397 mg kg⁻¹ dry weight DW. Though the limit of Mn in sediments is 5 according to WHO, in larger amounts, and apparently with far greater activity by inhalation, Mn can cause a poisoning syndrome in mammals, with neurological damage which is sometimes irreversible [52]. Victims of Mn poisoning suffer from cerebella dysfunctions as well as awkward, high-stepping gait [53]. Results showed that Site 3 gave the highest value reaching 397 ppm while the lowest was found in Site 1 (237.5 ppm).

Table 5 Total and available concentration of some heavy metals (ppm) in the studied soil and sediment samples

Recorded significantly low concentrations in Site 1 and Site 5 could be attributed to a big part of heavy metals in sediments being released back into the water compartment in the process of remobilization. Generally, there was a decrease in concentration down the river probably due to heavy metals remobilization back into the water and uptake by plants along the drain [54, 55].

Zinc (Zn) in sediments

The mean of Zn concentrations from sediments within the season are recorded in the same table. Zinc ranged between 69.7 and 166 mg/kg in different sites. Zn of sediments sampled from all the sites exceeds the permissible limit of 5 mg/kg according to WHO. Sediments are, however, known to accumulate more heavy metals with time that might be remobilized back to the water and the food chain [54, 55]. While Zn is crucial to plants and living, prolonged exposure to high intakes of zinc results in copper and iron deficiency and subsequent anemia [56].

Significant differences were reported in Zn levels between the sites, with Site 3 (166 mg/kg) recording significantly high levels compared to permissible level (5 ppm). This result is possibly due to plantations that might emit zinc compounds from either natural sources, or probably from agricultural runoff where phosphate fertilizers are used [57]. Sampling from Site 2 recorded significantly low concentration (70 ppm) and located downstream could have resulted in heavy metals remobilization back to the water and uptake by plants along the river [54, 55]. Based on the data and toxicity of Zn, constant monitoring was recommended to protect mankind who use the water or fish from the contaminated drains.

Chromium (Cr) in sediments

The mean chromium concentrations are recorded in the same table. Cr was ranged between 29.3 and 52.8 mg/kg in all sites studied. Though the levels were over the acceptable limit by FAO/WHO of 37.5 mg/kg DW for Cr in sediment in sites 3, 4 and 5, it was also found that all the sites recorded Cr levels that were significantly different. Sampling sites 1 and 2 were 29.3 and 30 mg/kg, while sampling sites 3 and 5 were 52.8 and 41.3 mg/kg, recorded significantly low and high concentrations, respectively. The significantly high concentration in sampling Site 3 that was located amidst El-batts drain could be attributed to industrial and urban waste. Sampling of Site 1 with significantly low Cr concentration was located in the beginning part of the drain and possibly had not received industrial or residential waste.

Comparable Cr levels in control with the ongoing study showed that Site 1 and Site 2 were down the WHO permissible level while the rest of the samples taken were significantly over the level. In the aquatic ecosystem, sediments serve as the primary reservoir for organic and other inorganic pollutants [58]. Contaminated heavy metal sediments can affect potentially the water characters and influence metals bioaccumulation in aquatic living, with possible long-term consequences on health and the ecosystem [59]. Sediment samples from El-Batts higher than permissible level contained very high significant amounts of chromium when compared with control (0.006 mg/kg) and fish (0.386 mg/kg) [60]. A constant monitoring program to assess Cr impact on the ecosystem was therefore recommended.

Nickel (Ni) in sediments

The mean of Ni levels for all considered sampling sites is recorded in Table 5. Nickel mean concentrations ranged between 11.5 to 25.5 mg/kg. All sites recorded significantly different nickel concentrations with sampling Site 3 recording significantly high concentrations of 25.5 mg/kg. Sediment sampling taken with high Ni concentrations, the residential wastes could be contributed to elevated levels of Ni concentrations in some sites. The significantly low concentration in Site 1 and Site 2 samples located in the beginning of the drain could be attributed to the remobilization of the metal back to water and plant uptake [61]. Nickel metal from drain sediments could be a contributing source to the levels in irrigated vegetables which require constant monitoring as elevated levels have been reported to cause sub-lethal effects [62].

Higher Ni mean content than the control or other sites could be attributed to the discharge of huge tannery waste and less rainwater as the main reasons for the high Ni concentrations. Sediment is the ultimate depository of many chemical compounds including heavy metals from natural and anthropogenic sources. Other possible sources of Ni in the water that led to the metal accumulating in the sediments include the combustion of fossil fuels, old battery wastes, components of automobiles, old coins, along numerous other items containing stainless steel and other Ni alloys [63].

Indices selected to express heavy metals status

• Zn equivalent calculated in El-Batts sediments

Results in Fig. 2 imply that ZE value in sites 3, 4, 5 exceeds the critical level (250) with numerical values reached to 461 in Site 3, 344 in Site 4 and 326.3 in Site 5, respectively. In sites 1 and 2, Zn equivalent values were 212 and 211.6 with no risky situation. Increasing the ZE values over the critical level of sediments has a bad environmental impact on the aquatic ecosystem and aquatic life [35].

• Contamination factor and degree of contamination

Fig. 2

Zn equivalent of the studied sediments at different sites

The variability of potentially toxic elements in sediments can be natural or influenced to some degree by anthropogenic activities. Since the metals coming from these activities usually accumulate and are sorbed within the fine part of the sediment, the study of enrichment factors requires previous compensation or normalization of grain dimension on the metal variability in different textural samples. Another factor to be considered in the establishment of enrichment factors for studies on contaminant elements in estuarine and/or marine sediments is the geochemical background. This value will be fundamental to distinguish whether an element existent in the ecosystem appears naturally or, on the contrary, is influenced by anthropogenic activities [64, 65]. Cf limits could be summarized as follows: down 1 (low contamination); between 1–3, moderate contamination; between 3–6 considerable contamination; and over 6 represents very high contamination status. Where, Cd down 1 low contamination; between 1–2 moderate contamination; between 2–4 considerable contamination; over 4 very high contamination degree.

Results in Table 6 cited that the numerical values of Cf ranged between low and considerable degree of contamination. The computed values of Zn ranged between 2.18 and 5.19, the minimum value was observed in Site 5 and the maximum was in Site 3 (5.19) meaning considerable contamination status. Cf of Cu ranged between 0.8 in Site 2 to 3.03 in Site 3 which represents moderate contamination status. This result was noted in almost all sites including Site 5 in Pb, Cr, Ni and Cu. The highest value was found in As Site 2 with a numerical value equal to 7.2 or very high contamination status, this result is possibly due to the human or industrial activities adjacent to this site.

Table 6 The contamination factor (Cf) and degree of contamination for heavy metals in the studied sediments

Cd values represented in the same table declare the hazards of heavy metals in sediments on aquatic ecosystems. Results showed that all studied sites showed very high Cd declares the poor standing of sediments of El-Batts and also showed the risky situation of aquatic life in this region.

Major chemical, physical and biological characters of soil-irrigated with LQW for varied extended periods

Salinity hazards

Salinization and sodification of soils are common mechanisms that define dry lands in particular. These processes are credited either to natural circumstances or anthropogenic activities. While natural causes such as climate, lithology, topography, and pedology, human causes are mostly related to agricultural land-use, and specifically, to irrigate agriculture. Results in Table 7 noted that the EC_e of selected soil samples ranged between 2.48 and 4.36 dS/m along El-Batts in surface and subsurface soils. In Site 5, the EC_e of the surface soil is 4.34 while the subsurface is 4.36 dS/m. It ought to be mentioned that Site 5 gave the highest EC_e values compared to other sites.

Table 7 Soluble salts (EC_e) and soluble cations and anions (meq/kg soil) of the studied soils as influenced by irrigation water quality

Cations and anions measured in the studied soils showed an elevation in Na⁺ cations compared to other cations. The numerical values of Na ranged between 15.81 and 31.13 meq/kg soil; again, the maximum values were observed in Site 5, with Na concentrations equal to 31.13 and 28.37 meq/Kg soil. Calcium Ca²⁺ cation takes the 2nd order in cation values after Na⁺; results showed that Ca²⁺ values ranged between 3 and 8 meq/kg soil in surface and subsurface soils, with the maximum values equal 8 meq/kg soil in Site 5. It should be mentioned that Mg²⁺ and K⁺ gave a lower value than Na⁺ and Mg²⁺. Increasing Na⁺ cation in the soil solution may explain the increase of soil pH to reach 8.5 (alkaline conditions) in the surface (0–30 cm) soil of Site 5 and values ranged between 8 and 8.5 in other sites.

Concerning the anions values, results showed that SO₄²⁻ gave the highest values compared to other anions measured. Values showed that SO₄²⁻ concentrations ranged between 8.33 and 19.80 meq/kg soil with very little variation between soils at the surface and subsurface, and increasing the values of Site 5. In the 2nd category, the measured Cl⁻ values ranged between 7 and 15.33 meq/kg soil with a significant increase observed in Site 5 and in surface (0–30 cm) compared to subsurface (0–60 cm) soils (15). Bicarbonate HCO₃⁻ takes the 3rd category in values ranging between 3.48 and 5.70 meq/kg soil and null values of CO₃²⁻ in all soils at the surface and subsurface.

Cl⁻ increases the osmotic potential of the sap and reduces water availability in the leaf tissue for plant metabolism. Symptoms of Cl⁻ toxicity are burn and dry leaves. At the same time, Na⁺ ions are absorbed by the soil and, thus, are not absorbed as readily as Cl⁻ ions. Also, Na⁺ competes with other cations for absorption by plants. Therefore, high K⁺, Ca²⁺, and Mg²⁺ concentrations reduce Na⁺ uptake by the plants. However, if Na⁺ concentration exceeds the plant-specific threshold in the leaf tissue, the effects and symptoms of Na⁺ toxicity are the same as for Cl⁻ toxicity [34].

Heavy metals content in the studied soils

There is an ever-increasing awareness and concern about the environment and the extent of the interrelationships between the three basic resources: land, water, and air. A seemingly removed input into one of these resource assets can be detrimental to another. In light of the environment’s immensity and the relatively low use rate, interests have generally been centered on other daily activities. Recently, a considerable degree of worldwide concern has been developing regarding the influence of heavy metals on the environment.

Because soils are heterogeneous, numerous studies have concentrated on the interaction of several heavy metals with different soil constituents. Thus, accurately describing the complex interactions of heavy metals in the ecosystem of soils is a prerequisite to predicting their behavior in contaminated soils. Specifically, to reveal the heavy metal’s fate in soils, one must account for the retention and release reactions of the varying species in the soil environment [39]. Soil’s heavy metals can take part in several complicated bio-chemical interactions, comprising dissolution and precipitation, oxidation–reduction, surface-solution complexation, and volatilization [38].

Generally, results indicated that all pollutants studied in soils regardless of their land use were over the permitted levels given by FAO/WHO. It is obvious in Table 5 that there are definite remarkable chronological fluctuations in the estimated soil characters linked with mixing groundwater with sewage effluent in irrigation for varied periods at the different studied cultivated sites. Similar fluctuations in soil characters were also recorded in surface and subsurface soils at each site owing to the leaching effect associated with irrigation with groundwater. In certain instances, nevertheless, the soil properties, texture in particular is the principal factor that discriminatory directly other characters of the soil environment.

Results documented in Table 5 show the heavy metals available form, generally Zn, Ni, Cu, Cr, B, Mn and Fe concentrations in selected soils were high in contrast to other heavy metals like As, Cd, and Pb. In addition, Fe was the highest compared to other contaminants and reached 27.70 ppm in Site 5. The identical pattern was also recognized in total form. In all farms, the highest values, however, were found in the surface (0–30 cm) soil layer compared to sub-soil.

Available manganese (Mn) in all farms was found to be significantly higher than other pollutants after Fe in the surface (0–30 cm) soil layers reaching 25.47 ppm in Site 5, which might be owing to irrigating with a mixture of industrial and sewage effluents in the end of canal. This result was reconfirmed compared to other pollutants studied.

Available Zn followed the Mn up to 21.27 ppm. It ought to be mentioned that these contaminants widely exist in different industrial issues. It should be also mentioned that Ni and Cu concentrations were significant in soils ranging between 6.23 and 10.47; 4.90 and 9.47 ppm in Cu and Ni, respectively.

The total of heavy metals concentrations in different investigated soil ecosystems in the same table showed a significant increase in most contaminants over the acceptable levels documented by FAO/WHO in soils of both surface and subsurface. In general, results showed a significant increase in the above-mentioned soil samples with significant concentrations of Fe ranging between 14,880 and 26,958 ppm. The maximum total of Mn and Zn concentrations ranged between 364.50 and 80.77 ppm followed by 26.43 and 41.57 for Cu and Ni, 145.03 and 35.40 for Cr and B and 2.63 and 3.05 ppm for Pb and As. It should be mentioned that Cd gave insignificant values in the soils studied.

Estimated Zn equivalent in the selected soil sites

Heavy metals retained in soils increased as time went on through the calculated Zn equivalent ZE model which showed variation ranged values. The evaluation of the pollution status would mainly depend on ZE with a reference of 250 as a critical level [35]. Any given soil with a ZE value higher than such level is suffering from pollution. Results in Fig. 3 noted that all samples at all sites were over 250. Numerically, ZE values were 290.33 and 254.30 in soils of surface and subsurface for Site 1 increased to 337.07 and 306.57 in Site 2 and again increased to 384.27 and 398.90 in Site 3. The maximum values were observed in Site 4 and Site 5 reached 448.93 and 468.63 in Site 4, and 427.53 and 449.80 in Site 5.

Fig. 3

Zn equivalent of the studied soils at different sites

In conclusion, under these conditions, it is expected that any crop cultivated or any edible crop in these farms especially in Site 4 and Site 5 would be unsafe for humans.

Kinetics of some inorganic pollutants desorption from the polluted soils adjacent to El-Batts drain

Heavy metals desorption from the ecosystem of soils is among the series of rate processes that govern pollutant(s) uptake by plant roots and subsequent depression in plant growth. Therefore, the study of soil-heavy metals release is considered an excellent tool for assessing the soil health status [39].

In this part, metals were kinetically studied from used soils being the most effective parameters to express heavy metals status in soils irrigated with sewage or industrial effluents. Results presented in Table 8 and Fig. 4 showed desorption of the studied metals from used soils, the studied heavy metals desorption rate was divided into three reaction periods; the 1st period was characterized by rapid reaction starting from the release reaction and reached about 30 min, the 2nd period characterized by decline in heavy metals desorption from different soils, this period take about 90 min started from 30 to about 120 min from the beginning of reaction time. The 3rd one, however, takes the rest of the reaction period and is characterized by almost steady state conditions or light increase in the rate of desorption (slow step) regardless of the heavy metals type.

Table 8 Rate constants of Zn, Cu and Ni desorption from polluted soils in mg/kg/min

Fig. 4

Some heavy metals desorption release from the studied soils at different sites

In 1st period, almost no noticeable differences were observed between the desorption of different metals in different soils, and a rapidly increasing desorption rate was detected for all heavy metals. However, in the 2nd and 3rd periods, the variation in the desorption of these pollutants from different soils was detected, in a high rate of desorption observed in Fe followed by Mn, Zn, Cu, Ni, Cr, B, As, Cd and, to less extent, Pb. Iron and Manganese exhibited Group 1 (high desorption release heavy metals); Zinc (Zn), copper (Cu), Nickel (Ni), chromium (Cr), and boron (B) represented Group 2 (moderate desorption release heavy metals); arsenic (As), Lead (Pb) and cadmium (Cd) represented Group 3 (low desorption release heavy metals). Generally, it was noted that Site 5 was the supreme site with all the heavy metals release except boron which showed a high release case from Site 4.

Rate constants of best-fitted models describe inorganic pollutants desorption from the polluted soils

Table 8 represents the rate constants of modified Freundlich (MFE) and Elovich models, the best-fitted models to describe Zn, Cu and Ni from soil samples gathered from the 5 sites. Both models gave highly significant R² ranging between 82** to 90** and from 87** to 95** for MFE and Elovich, respectively, for Zn; 0.88** to 0.92** and 95** to 96** for Cu, the respective values for Ni, however, for Ni were 0.87** to 0.91** and 0.91** to 97** for both models. The MFE was the best compared to the Elovich model for having lower standard error SE in all cases studied.

The rate of Zn desorption represented by kd value varied between different sites, for example, kd values was 0.20 mg kg⁻¹ min⁻¹ in Site 1, and increased to 0.32 mg kg⁻¹ min⁻¹ in Site 2, this result might be due to the light texture of soil collected from Site 2 (Table 9). For the same rationale, kd value decreased to 0.18 mg kg⁻¹ min⁻¹ in Site 5 where the clay (heavy) content increased from 11.62% in Site 2 to 66.39% in Site 5 (Table 9). The effect of soil properties on ions desorption or sorption was studied by different authors [39, 66].

Table 9 Nutritional status and particle size distribution of the studied soil samples

The β value was found to be inversely proportionate with the supplying power of the tested soils [67] and therefore could also be regarded as an index to ion-bioavailability if the rate processes of ion-release demonstrated to be the limiting step for plant uptake. In this respect [68] showed that β values vary widely with the soil and the decrease in β enhances the rate of ion-release reaction and that the Elovich was the best of other kinetic equations describing the rate reaction and it is convenient to compare reaction rates in different soils using the constant β of Elovich equation. Sikora [69] and Calderón-Garcidueñas [70] obtained a significant negative correlation between β and ion-bioavailability of water-insoluble forms of ions to grown plants. Results in the same table showed that β values slightly increased in Site 2 and Site 5 compared to other sites, this result perhaps could be related to the texture of these soils compared to other sites and also could be related to the increasing percentage of organic matter.

Although the same pattern was observed in other studied pollutants, the release of Cu and Ni could be higher than Zn in the studied sites in both models.

Microbiological evaluation of El-Batts drain water, sediments and its adjacent soils

Generally, assessing enzymatic activities of soil and water microorganisms has been employed extensively to ascertain the soil and water health in contaminated ecosystems. Enzymes produced by microbial consortium usually perform as catalysts for many processes that naturally happen in an environment as recycling of organic matters, elements and salutes, detoxification and elimination of xenobiotics, as well as increasing the availability of minerals to plants and other biotas which is responsible for keeping the necessary equilibrium between different microbial types. Researchers attempt to specify microbial enzymes as indicators for assessments of soil and water health. Monitoring microbial enzymes like dehydrogenases, lipases, ureases, and peroxidases was proven reliable to assess the soil quality that was contaminated by hydrocarbons [71].

Dehydrogenase is a common enzyme that is produced by all living microbes as a reflection of their activity within an ecosystem. Determination of dehydrogenase is the most common, quick and simple method for assessment of soil and water quality [72]. DHA is usually determined by the reduction of one of tetrazolium salt, 2,3,5-triphenyl tetrazolium chloride (TTC), to form the red-colored triphenyl formazan (TPF), and subsequently to be extracted from the cells by repetitive washing with methanol.

Urease as an enzyme generated from many microbes, especially soil microbes, that hydrolyze urea into ammonia and CO₂. Urease has been widely used for many biotechnological and environmental applications [73]. Many aerobic bacteria were known to produce urease, as Enterobacter, Proteus, Pseudomonas, Lactobacillus, Clostridium, and Serratia. The production of urease by soil microbes is crucial to stabilize the soil structure in the existence of calcium, that known by the soil calcination process. When urease is released by soil microbes in the presence of urea, urea disintegrates into positively charged ammonium NH₄⁺ and negatively charged carbonate group CO₃²⁻, thus raising the soil pH and starting the precipitation of CaCO₃ [74].

Microbial peroxidase is among the enzymes that are essential for the survival and multiplicity of microbes in the heavily contaminated environments. Peroxidase enzyme is not only functions with the lignin polymerization process, carried out by soil bacteria, but also works on scavenging the free oxygen radicles (ROS), under stressful environmental conditions such as the existence of xenobiotic or heavy metals. Soil and water microbes are sensitive to the existence of pollutants in the same environment, so peroxidase enzyme can be tested to assess the microbial activity and further determine the contaminated ecosystem quality and health [75].

Peroxidase activity can be measured calorimetrically in the existence of indicator (pyrogallol) and H₂O₂, where pyrogallol is oxidized due to H₂O₂ decomposition. Peroxidase is measured by units for the decay of 1 µM H₂O₂, corresponding with the production of 1 peroxidase unit per minute [76].

Results in Fig. 5 represent the three enzymes’ activities (dehydrogenase, urease and peroxidase) in five different sites of El-Batts drain in the period between September 2021 to June 2022. Generally, it is observed that the enzymatic activity of both dehydrogenase and urease, in the five sites increased in September followed by a decrease in the winter months (January and March) which then reached their outmost activity in the summer month (June). These results can be explained by fluctuations regarding the water temperature and the influence of the surrounding temperature (cold or hot) on the indigenous microbes’ activity and further hydrolytic enzymes production. On the contrary, peroxidase enzyme values showed a low decrease from September to June which can be explained by other abiotic factors when assuming the same contaminants concentrations. Moreover, the obtained results indicated that site (S5) was supported with the most potent microbial community, illustrated by dehydrogenase, urease and peroxidase values (10.98, 13.03 and 0.33), respectively.

Fig. 5

Biological activity of the studied water at different sites at different periods

Tables 10, 11 represent the three enzymes activity in water, soils and sediments of El-Batts drain. Similarly, the results exhibited that site (S5) showed the highest enzymatic activity for soil samples (19.09, 12.38 and 15.54) and for sediment samples (16.52, 22.34 and 15.05) for dehydrogenase, urease and peroxidase results, followed by S3 and S4 sites, respectively.

Table 10 Total, fecal coliform and salmonella count in irrigation water (CFU) at different studied locations at different periods

Table 11 Some biological analysis of the studied soil and sediment at different locations

Additionally, there are other parameters for the detection of water and soil quality, than the detection of enzymatic activity, which correlated directly with the presence of microbes including the assessment of COD, BOD and DO.

The activity of microbes within an environment depends on the ability to oxidize and utilize the organic material in this environment which can be estimated by the detection of both COD and BOD concentrations. Moreover, the concentration of DO is directly influenced by microbial activity, in the way that the higher DO concentration, the greater microbial activity and further optimization of the surrounding environment’s health.

Figure 5 exhibits COD, BOD and DO values in five sites of El-Batts, which confirm the outputs of (Table 10 and Fig. 5) about the microbial activity indicators data. COD and BOD values were the most in June than any other month with the priority to sites S5 and S3 as their values were (750 and 750) for COD, and (566.8 and 253.2) for BOD, respectively.

In contrast, DO results were variable, as the highest results were detected for S1 and S2 in comparison to other sites. Moreover, in the winter month (January), the highest DO results for all samples were recorded which is explained by the low microbial activity in this month that utilizing the existing oxygen is considerably lower and the available concentration is reasonably higher than any tested month.

Detection of the pathogenic bacteria in El-Batts water, sediments and soil samples

The existence of fecal bacteria represents one of the main challenging contaminants for removal or even complete elimination from the water ecosystem. Table 10 shows total fecal bacteria and Salmonella from samples derived from five different sites in El-Batts drain.

In response to the increased temperature in autumn where it reached its optimum in summer, water samples taken in both months September and June were recorded to contain the highest numbers of pathogenic bacteria illustrated in Table 10. Salmonella count were considerably lower than fecal bacteria counts that were only detected in samples S5, S4, S3. Also, samples taken from sites S3 and S5 were recorded to be the highest for total fecal bacteria count (4 × 10⁷ and 8 × 10⁶), respectively.

Table 11 illustrates total bacteria count, total fecal count, and Salmonella count in five sites (soils and sediments) from El-Batts drain. As confirmed from the previous results, site S5 was estimated to be the highest for the three parameters for soil (8 × 10⁷, 3 × 10³ and 1 × 10²), and sediments (7 × 10⁸, 5 × 10⁶ and 0), respectively.

Results from the previous analysis (Tables 10, 11 and Fig. 5) confirmed that S5 followed by either S3 or S4 were highly contaminated with organic matters and pathogenic bacteria, so these sites were chosen for further investigations to find a suitable bioremediative technology.

Conclusions

This study is considered an introduction for clarifying the problems of the irrigation with low-quality water in order to develop different strategies for treating water in the El-Batts drain and adjacent farms irrigated with this low-quality water at Fayoum Governorate.

Considering the findings and data analysis of El-Batts water, sediments and soils adjacent to the drain, we can conclude that:

• The current state of the drain and its adjacent farmlands are “heavily polluted”. The agricultural crops produced are unsafe for human consumption, El-Batts water is unsuitable for using in irrigating crops or agricultural activities, depending on IWQI which showed poor water grade throughout the four seasons. It also showed the majority of physiochemical and biological indices, especially salinity (potential salinity PS and Kelly ratio KR), in all the studied sites along the drain, exceeds the acceptable levels of the Food and Agriculture Organization FAO, the World Health Organization WHO and the Guidelines of the Egyptian Governmental Law.

• The study also showed contamination of the adjacent soil and sediment, both exceed the critical levels of indicators (Cf, Cd and Zn. Equivalent ZE), and the chemical and the biological characteristics were also deteriorating and worse than expected, especially the microbial enzymes production (necessary for maintaining wastewater quality), and the pathogenic bacteria existence like (Salmonella, and fecal coliforms bacteria), and the content of inorganic pollutants (heavy metals). This might threaten the environment of the aquatic life not only for the drain itself but also as far as in the lake of Quaroun, which receives all the El-Batts drain effluents including its organic and inorganic pollutants.

• Results also showed that Site No. 5 represented the most polluted site along the drain, however, all other sites need more attention of monitoring and further remediation, which will be discussed in detail in the upcoming studies.