Summary of the performance of all the CETPs in Surat

The percentage BOD reduction by the CETPs in Surat is generally better than that of Ahmedabad and the exceedance factor of the treated BOD is less when compared to the CETPs in Ahmedabad. Another important difference is that negative reduction in the BOD is generally not seen in the case of the CETPs in Surat, unlike those in Ahmedabad. The lower concentration of effluents in Surat is due to the textile sector—which happens to generate a larger volume per industrial unit but has a lower concentration of pollution in comparison with the chemical sector. The performance of the CETPs with respect to the BOD and the COD is summarised in Table 10.5. For the study period, though the average values for none of the CETPs in Surat are able to meet the norms for the COD for treated effluents, the exceedance factor is far less when compared to that of CETPs in Ahmedabad.

TABLE 10.5 Summary of the performance of the CETPs in Surat

Source: The table has been compiled from the analysis in the previous sections.

There have been instances of illegal discharge of industrial effluents into khadis or storm drains which finally meet the khadis in Surat—these have been discussed in the relevant places. The improved performance of the CETPs in the year 2017, as a result of the NGT order, has also been noted at the appropriate junctures.

Environmental infrastructure for sewage treatment

The sewage discharge from the city is another major source of pollution of water bodies. In Surat, there are ten operational sewage treatment plants (STPs) spread across the city. The final discharge point for these STPs is one or the other creek and there is only one STP which discharges into the Tapi.

The details of the STPs with respect to the capacity, the year of commissioning and the discharge point for treated sewage is summarised in Table 10.6. The details of the discharge points have been summarised from the permissions issued to the STPs by the GPCB under the Water Act. Some of the STPs are very old and have been undergoing upgradation (https://www.suratmunicipal.gov.inZD epartments/Drainagelntroduction accessed on 21 June 2019).

The Bamroli STP was designed to treat sewage for reuse by the industrial units in GIDC Pandesara. However, the operational part could not be verified. The last capacity addition for the STPs happened in the year 2012. The capacity of the STPs more or less matches with the sewage generation in the city. The point to investigate further is whether the performance of the STPs meets the prescribed standards.

The GPCB collects the samples of the treated sewage from the STPs once in a while. A summary of the available analysis reports for the period ofjanuary 2018 to June 2019 is presented in Table 10.7.

Over a span of one and a half year, there have been, at the maximum, five samples from an STP collected by the regulator. Most of the samples meet the

TABLE 10.6 Sewage treatment plants in Surat

Source: Compiled by the authors from data collected from different sources (GPCB Annual Reports; Consent Orders issued to the STPs; CPCB, 2015).

TABLE 10.7 Performance of the sewage treatment plants in Surat

Source: Unpublished data from GPCB.

norms except for suspended solids (SS). The almost negligible monitoring of the STPs indicates that the focus of the GPCB is on industrial pollution.