Introduction

The advancement of a country depends upon its industrialization. But water pollution caused by industries is a serious concern throughout the world (Braio and Taveres, 2007; Mustafa et al., 2010). Of all industrial sectors, the food processing units have highest consumptions of water and are biggest producers of effluent per unit of production (Ramjeawon, 2000; Prabhakar et al., 2006; Tikariha and Sahu, 2014). Safe disposal of industrial effluent has become an ecological challenge. Continuous disposal of waste water into the water bodies has deteriorated surface water quality because of the mixing of various chemical pollutants of the effluent with water (WHO, 2003; Al-Dulaimi et al., 2014; Khaleel et al., 2012). The physico-chemical techniques used for removing pollutants from the environment are inefficient, costly, of limited applicability, and sometimes producing large amounts of toxic waste which is difficult to dispose off or form hazardous by-product. The lack of efficient effluent treatment facilities and proper system of waste water disposal has increased pollution of water bodies day by day and adversely effected soil, water, flora and fauna due to presence of toxic and persistent chemicals.

The industrial effluent has been used for agricultural irrigation in developing as well as developed countries. The soil has a great capacity for receiving and decomposing various types of wastes and pollutants and thus it act as an excellent purifying media. The land disposal of agricultural, dairy, municipal and industrial waste is widely practiced as a major and economic source of nutrients and organic matter for growing cereal in arid and semi-arid regions of the country, where shortage of water becomes limiting factor (Gaikar et al., 2010). Further, the industrial effluent is rich in plant nutrients and can be effectively utilized as liquid bio- fertilizer for the soil restoration and sustainable land production.The usage of the treated effluent for recreational activities is due to the demand of the water worldwide. Thus, Finding suitable eco-friendly techniques for the potential utilization of these released effluents as a source of nutrients become essential (Parmar et al., 2017). The effluents generated from food processing industries like fruits and vegetable processing, meat and poultry processing, dairy industries etc are rich in nutrients like carbohydrates, minerals and nitrogenous compounds which when supplied in optimal concentrations enhance the plant growth (Kumar, 2011; Kumar et al., 2013).

In India, dairy industry is one of the most important agro-based industries and is important commodity entering trades. The dairy operations involve processing of raw milk into pasteurised and sour milk, hard, soft and cottage cheese, cream and butter products, ice cream, yoghurt, milk powders, condensed milk and various types of dessertsfor the consumer.Enormous amount of water is used in various stages of dairy operations, such as, milk processing, cleaning, packaging and cleaning of the milk tankers and resulting in generation of significant quantities of waste water which is known as dairy effluent (Belyea et al., 1990; Manu et al., 2012). The quantity of dairy effluent released by a milk processing plant depends upon the size of the plant, generally expressed in terms of the maximum weight of milk handled in a single day, and the processes involved.The dairy industry generates on an average 6-10 litres of waste water per litre of the milk processed. It has relatively high organic matter, suspended solids, trace organics nutrients, inorganic nutrients which are essential for growth of crop plant (FAO, 1992; Kharbanda and Prasana, 2016; Verma and Singh, 2017).

The present investigation was carried out to study the effective and suitable concentrations of dairy effluent in promoting germination, wet weight and dry weight of mung bean (Vigna radiata) and mustard (Brassica nigra). The study also aimed at physicochemical characterization of effluent from Jaipur dairy.

Materials and Methods

2.1.  Experimental procedure

The study was conducted in biotechnology laboratory at the Kanoria P. G. Mahila Mahavidyalaya, Jaipur to study the effect of dairy effluent on the germination of seeds of mung bean (Vigna radiata) and mustard (Brassica nigra) in November 2019. Maximum temperature during the study period varied between 18°C – 32°C.

2.2.  Sample area and sample collection

The effluent samples were collected from Jaipur Dairy from a discharge point in a clean plastic container which was rinsed with HNO₃ and distilled water. The sample container transferred to biotechnology laboratory and stored at 4°C until used for further analysis.

2.3.  Physicochemical characterization of dairy effluent

Effluent samples were analyzed for physico-chemical parameters such as pH, temperature, salinity, nitrate, BOD and COD by standard protocols given in American Public Health Association (APHA) (1998). Color, temperature and pH of the effluent were recorded at the sampling point. All other parameters were analyzed within 24 hrs.

2.4.  Seed germination experiment

Effluent samples were analyzed for physico-chemical parameters such as pH, temperature, salinity, nitrate, BOD and COD by standard protocols given in American Public Health Association (APHA) (1998). Color, temperature and pH of the effluent were recorded at the sampling point. All other parameters were analyzed within 24 hrs.

2.4.  Seed germination experiment

The healthy seeds of Mung bean and Mustard were selected and surface sterilized with 0.1% mercuric chloride (HgCl₂) and washed with distilled water. Twenty seeds were placed equispacially in sterilized petriplates which were lined with filter paper soaked with different concentrations of effluent (20%, 40%, 60%, 80% and 100%) and tap water as control. These petriplates were irrigated with different concentration of effluent uniformly. Number of seeds germinated was counted on 7^th day and total growth parameters viz., the germination percentage, the shoot length, dry weight and wet weight were calculated. The shoot length was measured at the area of contact between the stem and root; mean shoot length was expressed in centimetres using a measuring tape (cm). The wet weight of seedlings was taken and then they were dried overnight in oven and again weighed for estimation of the dry weight. Data were taken from three replicates of seedlings.

2.5.  Statistical analysis

The values of different parameters are presented as mean of replications. The treatments were designed in completely randomized block design with three replications. The statistical analysis was done by using online software OPSTAT.

Results and Discussion

3.1.  Physicochemical characterization of dairy effluent

From the data presented in Table 1, it is clear that dairy effluent was white in colour. The pH and temperature of the effluent was recorded as 6.8 and 26^°C, respectively. These results were similar to the findings by Dhanam (2009) for dairy industrial effluents. Dairy waste streams have higher annual temperature (17–25°C) than that of municipal waste water (10–20°C), thus, a faster biological degradation occurs in dairy waste water as compared to sewage treatment plants (Ahmad et al., 2019). The values of alkalinity, chlorides, nitrate, BOD and COD of the effluent were 1.93 mg l^-1, 260 mg l^-1, 22 mg l^-1, 310 mg l^-1, 680 mg l^-1, respectively.

Table 1: Physicochemical characterization of dairy effluent

3.2.  Seed germination experiment

Among various concentrations ranging from 20% to100%, the dairy effluent samples showed favourable effects on seed germination and other growth parameters of both mung bean and mustard. The results presented in Table 2 revealed that among various effluent concentrations, maximum percent germination of seeds of Mung bean (97%) in petriplates was observed with 20% effluent concentration which is statistically at par with that of control (tap water), 60% and 80% effluent concentration.

Table 2: Effect of different concentrations of dairy effluent on percentage germination of Mung bean seeds

The minimum germination (80%) of mung bean seeds was at 100% effluent concentration. Similar results were obtained in pots, the seeds of mung bean showed maximum percentage germination at 20% effluent concentration (84%) which was statistically at par with that of control and 80% effluent concentration. Lower concentration of dairy effluent showed promoting effect on seed germination, seedling growth, dry matter production (Dhanam, 2009). The minimum percentage germination (25%) was observed at 100% effluent concentration. Results of present investigation are supported by the previous work on black gram and green gram irrigated by dairy effluent (Prasannakumar et al., 1997). The promotion of seedling growth by lower concentration of effluent might be due to the presence of plant nutrient in the effluent.

In case of mustard seeds grown in petriplates, the highest percentage germination (100%) was recorded at 20% effluent concentration which was statistically at par with that of control (95%). In pots, the maximum mustard seed germination (52%) was recorded at control which was at par with seed germination  at 20% (48%) and 60% (45%) effluent concentration (Table 3).

Table 3: Effect of different concentrations of dairy effluent on the percentage germination of Mustard seeds

Conclusion

The effluent sample at low concentration (20%) showed a remarkable response in growth and germination compared to other concentrations. Since, the higher concentrations of the treated dairy effluent inhibits the plant growth, it is recommended that only after suitable dilution, dairy effluent can be effectively used for irrigation. However, some more extensive research work is needed to make such recommendation in order to minimize the risk.

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