INTRODUCTION

The Raigad District of Maharashtra State is a coastal belt located on Western hills of Sahyadri. Industrial growth has rapidly taken place in this District since 1970.MIDC has developed four Industrial Estates in Raigad district and one of it is developed at Dhatav in Roha Taluka. There are about 31 Nos. of water pollution potential industries comprising of bulk drugs, pigment, dyes & pesticide units etc. The industrial estate is located in A-II class of Kundlika river basin. About 10 MLD of industrial effluent is generated from the said industrial estate .Individual industries has set up their own effluent treatment plant & effluent treated therein, is further treated in CETP operational at Dhatav MIDC, which consist of primary, secondary & tertiary treatment units. The treated effluent is disposed by pumping, in Saline zone of Kundlika River at Arey Khurd at about 8.2 km distance from CETP through a closed disposal pipeline laid by MIDC authority.

The disposal of effluent at appropriate point in saline zone of river is a very important issue to protect the eco system, flora - fauna & the agricultural crops on the bank of river. Therefore, in order to safe guard river eco system, it is essential to ensure adequate dilution & proper dispersion of pollutants at disposal point. Further, the dispersion of pollutant is affected by tidal influence in saline zone or in creek. Effluent disposed at a point should not remain stagnant during tidal waves to avoid accumulation of Pollutants and subsequent impacts.

Existing disposal of effluent at Arey Khurd :

Effluent from MIDC Roha & sewage of town is discharged into Kundalika river in saline & drinking water zone respectively. The River Kundalika originates from Sahyadri mountain ranges & flows through various Talukas of Raigad District and along side of Roha MIDC and ultimately meets to Salav creek near village Salav. The main flow of river water is a discharge of tail race water from Bhira Hydel Power Project.

The stretch of river is divided into A-I, A-II & SW stretches. Though, MIDC Dhatav is located in A-II Class stretch of river but disposal of industrial effluent is in saline zone. The river has islands along its stretches and particularly at down stream of Arey Khurd where treated industrial effluent from CETP at Dhatav is discharged, which divides river into two ditches during low tide.

MIDC is disposing treated effluent from CETP at MIDC Dhatav at Arey Khurd in saline zone of river Kundlika at a distance of 8.2 km through a closed pipeline. In fact, MIDC, as per the recommendation of NIO, has laid down a pipe line of length 19.8 KM upto Mahadev Khar except in between patch of 3 km from Arey Khurd to Gopan village.

The disposal of treated effluent at Arey Khurd in saline zone is on left bank of the river on the land without diffuser system .Due to this effluent does not mix directly with the water of river but has to flow a few distance over a land before confluence with river water. As effluent is not mixing directly into the river water without the diffuser system, is causing stagnation of effluent and subsequently leading to accumulation of pollutants in river bed.. This present mode of disposal of effluent has resulted in complaints from farmers for the damage of crops. Present disposal point is not suitable as proper dispersion of pollutant does not takes place & there is obstruction in the form of island of length about 150 Mtrs. at the immediate down stream of the disposal point.

During low tide the river bed down stream at the disposal point become visible and divides the river into two ditches. At this stage, since disposal is on left bank of river the pollutants entirely flow along this bank only, without utilization of right bank for dispersion of pollutants. Therefore pollutant concentration increases on the left bank and causes smell nuisance.

Since disposal of effluent is on the land on left bank, the land at this point is deteriorating due to deposition of solids of effluent. The farmers from the down stream villages complains of ingress of river water along with effluent during high tide in their farm land & claim for compensation for damage to crop.

In view of above environmental problems the study of river water quality at the upstream & down stream of effluent disposal point at Arey khurd was carried out on 11/1/2007 to ascertain river water quality at upstream & impact of effluent disposal and the dispersion of pollutants on the down stream.

Survey :

A study was carried out to ascertain concentration of pollutants at the confluence point, dispersion of pollutants at various locations across the width of the river at the down stream of present disposal point at Arey Khurd in Kundlika river on 11/1/2007 during 7 am to 7 pm.

Sampling Procedure followed :

1. To carry out the survey three teams of one field officer & field assistant each were formed under co-ordination of Sub Regional Officer Raigad II & under the guidance of then Regional Officer Raigad
2. For collection of samples boats were hired and other sampling materials such as plastic Cans , HDPE drums and DO bottles were assembled at requisite location. Two liter capacity can was utilized for collection of samples.
3. The samples were collected from 7am. To 7pm on the day consisting of composite and grab samples. All samples of the river were collected from the surface of the river water.
4. Locations of sampling points at a distance of 100 mtrs. upstream of confluence point, at confluence point, 100 mtrs., 500mtrs., 1000 mtrs. down stream of confluence point were fixed from the disposal point on the river.
5. The width of river water at 100 Meters Up stream, 100 Meters, 500mtrs., 1000 mtrs. down stream from the confluence point was measured by rope using boat and the width approximately observed as 240 Mtrs, 233 Mtrs, 216 Mtrs & 250 Mtrs respectively.
6. The samples were collected across the width of river water at fixed downstream locations at a distance approximately at 1/3rd middle & 2/3rd distance of the river water width from left bank of Kundalika river.
7. During low tide the river bed at 100 Mtrs down stream of the disposal point was visible and river was divided in to left and right ditches and hence samples were not collected throughout the width of the river water during low tide. However, the samples were collected from the left ditch only (width approximately 70 to 80 Mtrs) at 1/3rd middle and 2/3rd distance.

The collection of sample was carried out as follows:

1. Grab samples of river water during peak high tide and peak low tide. (4nos)
2. Grab samples of river water for DO analysis at upstream & down stream and at confluence point (11Nos) DO samples were collected on the left bank of the river and DO was fixed on the site.
3. Composite samples of river water collected during high tide and low tide at upstream, confluence point and at down stream at an interval of 2 hrs. ( 22 Nos)
4. Grab sample of CETP inlet and outlet effluent (2 Nos.)

Total 39 Nos of samples were collected. These samples were submitted to central laboratory for analysis purpose on 12/01/2007.

Observations :

All river water samples were analyzed from Central Laboratory, at Mahape The results are tabulated as below:

Table 1 Grab sample Results (During peak high tide(HT) and peak low tide (LT)

Sr No.	Location	Results
		pH	BOD	COD	Chlorides	TDS
1	100mtr down stream Disposal point, peak (HT)	6.5	10	32	22	251
2	100mtr down stream disposal point, peak (LT)	6.7	12	32	40	297
3	1000mtr down stream Disposal point, peak (HT)	6.4	12	32	138	441
4	1000mtr down stream Disposal point, peak (LT)	6.4	11	24	254	516

Note :- All parameters except pH are in Mg/Liter.