Current Seasonal Variations in Physicochemical and Heavy Metals Parameters of Sewage Treatment Plant Effluent and Suitability for Irrigation

The study aims to investigate the current extent of physicochemical parameters and heavy metal contamination in the effluent of the Jaganpur sewage treatment plant (STP), Dayalbagh, Agra India. Majority of the nearby farmers have access to use of STP effluent in irrigation purposes for growing major edible crops. The problems of using STP effluent for irrigation purpose, continuous water quality analysis required. To check the quality of irrigation water, substantial physicochemical parameters accordance to Indian Standards (IS-Reaffirmed 2002/2003) analysed to calculate Sodium absorption ratio (SAR) and Residual sodium carbonate (RSC). To estimate the heavy metal pollution index (HPI) and metal quality index (MQI), toxic Heavy metals such as As, Cr, Mn, Fe, Ni, Cu, Zn, Pd, Cd, Co, and B also determined in the STP effluent with an AAS and results verified with ICP-OES against certified standards. The high value of SAR (range 13 to 20) and RSC (range −10 to 11) in STP effluent exceeded the permissible limit for irrigation purpose. On the other hand, HPI and MQI values (1692.4 and 58.1, respectively) show that high metal contamination mainly due to industrial and domestic wastewater does not treat appropriately in the sewage treatment plant. Thus it is suggested that further studies are carried out on the STP effluents to improve the water quality through proper treatment. Treated wastewater used for irrigation purposes needs to analyse the contamination like heavy metals and pinpoint the pollution sources.


Introduction
This Wastewater treatment is a global concern, critically interlinks to sustainable agriculture, animal and human health and environmental quality worldwide, including Indian subcontinent [1]. The Yamuna and many other rivers are getting polluted and contaminated on receiving the considerable quantity of untreated wastewater drained from urban and industrial sources [2]. Total wastewater generation from urban areas in India is above 39,000 MLD, out of which only 34% is treated [3]. Major Indian cities also extract effluent from sewage treatment plants (STP) for agriculture and industrial usage, therefore, quality of STP effluents stands critical from human, animal and crops health as well as an ecological point of view. In Agra, Jagnpur STP has a catchment area of over Farmer's especially poor and marginal one, lift STP effluent during the summer season due to the scarcity of river water. The efficiency of STP and the quality standards of its effluent show a significant impact on the quality of Yamuna water and irrigate crops which can be detrimental to crop quality, soil, human and animal health and environmental quality [3].
On the other hand, contamination of the Yamuna River by toxic heavy metals is a serious environmental problem and needs to be monitored regularly as heavy metals are toxic due to their non-degradable nature and bio-accumulation through the food chain. In many parts of the world, STP effluent or untreated wastewater is being used for irrigation in agriculture crops field without assessing its suitability leading to deterioration in the quality of soil as well as a crop [4] [5]. Toxic Heavy metal pollution index (HPI) helps identify and quantify trends in water quality concerning spatial variation in the concentration of heavy metals. The metal quality index (MQI) is computed to assess the suitability of water resources for drinking/irrigation purpose concerning metals [6].
Pearson's correlation analysis is a useful tool for the identification of pollution sources [7] [8].
In this backdrop, a study covering about whole Dayalbagh stretch conducted during 2014 at six sites in Agra districts of Uttar Pradesh state which dominantly beset with sandy loam soils, semi-arid climate and an annual rainfall of about 550 -750 mm. The already concluded studies on STP effluent quality indicate that fitness of water for irrigation of crops near Dayalbagh, Agra is highly variable and unpredictable concerning a location within city limits and time [9] [10]. Therefore, this study which involves a Sewage treatment plant and less studied stretch of 293.4 m was carried out to assess the suitability of STP effluent for ir-Journal of Water Resource and Protection rigation to crops during winter, summer, rainy and post-rainy seasons. This paper discusses the physicochemical properties, and heavy metal toxicity of STP effluent vis-à-vis designate irrigation water quality guidelines to indicate its fitness for crops for an advisory to the farmers.

Sampling Site
Sampling sites selected along 470.54 m stretches of Jaganpur STP (14 MLD) site in Agra districts of Uttar Pradesh (Figure 1(a)). Another site is connected with Jaganpur STP effluent for the irrigation uses of nearby farmers (Figure 1

Analysis of Physicochemical Parameters
Physicochemical parameters viz., pH, electrical conductivity (EC), ions concentration (boron, Na + , Ca 2+ , Mg 2+ , HCO 3− NO − ) were estimated in STP effluent, collected in pre-sterilised HDPE plastic bottles of 100 ml, following standard methods and procedures where calcium and magnesium (total hardness) determined by versenate (EDTA) Method, sodium ion determination carried out directly with the help of flame photometer and standard curves prepared by taking known concentration of Na + . The determination of Carbonates and bicarbonates (total alkalinity) and Chloride by simple acidimetric titration nitrate in water determined by phenol disulphonic acid method [11] [12]. At every sampling site, three samples collected, i.e., from influent, mid and effluent of the STP and one each at either side of STP effluent storage pond supplied to Dayalbagh community from about one-foot depth. These samples were composited and subjected to physicochemical and heavy metal analysis. The physicochemical parameters so determined compared with the standard irrigation water quality guidelines [11] [12], which has presented in (

Analysis of Heavy Metals
STP effluent samples collected from the Jaganpur "sewage treatment plant" at all three sites during all season. The samples collected in a manner of three composites taken from 1 foot below the water surface using pre-sterilized 500 ml bottles to avoid unpredictable changes in characteristics generally HDPE bottles used. STP effluent samples collected were placed at 4˚C in an ice-jacket and transported to the laboratory immediately for further analysis. The collected C. Maurya, J. N. Srivastava samples acidified with concentrated nitric acid to a pH below 2.0 to minimise adsorption and precipitation on bottles walls as required by the standard procedure. The concentrations of heavy metals determined using an atomic absorption spectrometry (Perkin-Elmer, 3300/96, MHS-10) after the acid-digestion procedure for heavy metals analysis. All analyses carried out in triplicate, and the results expressed as the mean. The overall quality of river water concerning the content of heavy metals assessed by HPI values and its critical value is 100. The weighted arithmetic average of the concentrations used to calculate HPI [13] values using the Equation (3).
where Wi = the unit weightage defined as the reciprocal value of Si. Si = the maximum permissible limit for irrigation water [14], and n is the where Mi = the monitored value of the heavy metal, Si = the standard value of the i-th parameter, in ppm (μg/L).
(The higher the concentration of heavy metals compared to its respective maximum permissible limit (Si), the quality of the water will be worse.) MQI value below one is a threshold of warning [10] [14], the MQI is calculated by Equation (5) The data were statistically analysed using the SPSS 20.0 statistical software package to calculate Pearson's correlation coefficient and level of significance (p < 0.01 and p < 0.05).

pH and Electrical Conductivity (Soluble Salts Concentration)
The pH of STP effluent found alkaline and register conspicuous variations at different sites and seasons (range: 7.6 to 9.6), however, it was most alkaline in rainy season (8.5 to 9.6), slightly alkaline in summer season (8.5 to 9.3) and moderate in post-rainy season (7.9 to 8.4) and winters (7.6 to 8.2). The irrigation quality guidelines suggest that at this pH range, degree of restriction on the use of water for irrigation can moderate to severe for all the crops and soil types. Earlier studies of [14] also well corroborate with these findings on STP effluent pH. EC at different sites followed the order: rainy (2.30 to 2.58 dS/m) > post rainy season (2.0 to 2.50 dS/m) > summer (2.0 to 2.5 dS/m) > winter season (1.8 to 2.1 dS/m). Higher EC during rainy may be a cumulative effect of more solubility of ions, higher domestic wastewater discharge on account of more con-Journal of Water Resource and Protection sumption of water, the higher flow rate from surface of water bodies and lower flow rate of the STP effluent. The lowest EC of STP effluent during the winter season can ascribe to low overflow runoff from STP and resultant proper treatment of dissolved ions that directly determine EC (Figure 2

Nitrate and Sodium
Nitrate (

Boron
Boron, an essential element for crop plants becomes toxic above critical levels [26]. Boron in STP water contributed via chemical weathering and anthropogenic inputs [27]. The concentration of boron in STP water followed seasonal   Table 2). The concentration of all heavy metals was highest at Jagnpur STP which due to the inefficient treatment of wastewater coming from the fertiliser and chemical industries and residential areas of the city. Heavy metals viz., Fe, Pb, Zn and B found within permissible limits for irrigation water quality at all sites. Whereas other heavy metals were above permissible limits for irrigation water quality, its source was wastewater coming from painting and electroplating industries located in the city. As, Cd, Cr, Co and Mn were found higher than maximum permissible limit for irrigation water quality at influent and effluent sites of STP which accounted due to Chemical, Municipal and fertiliser industries. Cu and Cd were found higher than the maximum permissible limit for irrigation water quality at effluent.
The HPI values determined using mean concentrations of nine heavy metals (Fe, Pb, B, Cd, Zn, Cr, Cu, Cd and Mn) ( Table 3). The critical value of the HPI is 100 [13]. The mean HPI for STP effluent for all-season means was found very high, i.e., 1692.4 indicating high heavy metal pollution. The high HPI values were mainly due to industrial and domestic wastewater does not treat appropriately in the sewage treatment plant. The metal quality index was used to estimate total metal pollution of STP effluent for irrigation. All sites along the studied stretch seriously threatened with metal pollution for irrigation (MQI > 1), MQI reached 58.19 at Dayalbagh site.
The Pearson correlation analysis for heavy metal content in STP effluent revealed that there were significant strong positive correlations (p < 0.05) between all the nine heavy metals (Table 4). A positive correlation between heavy metals analysed at different sites showed either an association/interaction between the

Conclusions
Our study on STP effluent for Agra stretch revealed that Jaganpur site highly polluted with heavy metals, alkalinity, hardness and other toxic ions. The results showed that the physicochemical parameters assessed to determine the SAR (13 -20) and RSC (−10 to 11) for STP effluent confirm to moderate to severe range of restrictive use for irrigation to crops fields. As such, a safer side practice, i.e., desired dilution and judicious use of polluted/contaminated STP effluent should follow in long-term use of water for irrigation of crops in the studied stretch for avoiding the adverse influences on human, animal and soil health as well as on environmental quality. HPI (1692.4) of STP effluent shows critically polluted with heavy metals and unsafe for irrigation in all seasons throughout the year. MQI (58.1) is much higher than the critical limit at all sites indicating severe total metal pollution. Pearson's correlation analysis showed that all heavy metals had a common source of pollution. The study will be useful in designing policies and action plans to concerned wastewater treatment management for pollution abatement and restoration of the used clean water. Sewage treatment plants efficiency to try and mitigate the inputs thereof and therefore develop the proper, effective eco-friendly methods to remediate the amount of toxicity entering the human bodies through the food chain.