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The stringency in effluent discharge and reuse standards has made it extremely expensive to discharge the effluents safely or reuse them. Therefore, existing wastewater treatment plants should be evaluated and improved or augmented. With this aim, five existing common effluent treatment plants (CETPs) in North India were evaluated, including: the State infrastructure Development Corporation Uttrakhand Limited (SIDCUL) Haridwar, which processes 4.5 Million Liters per day (MLD); the Industrial Model Township (IMT) Manesar Gurgaon, 55 MLD (comprising two streams of 25 and 30 MLD each); the Lawrence Road Industrial Area (LRIA), Delhi, 12MLD (12MLD LRIA); Mayapuri Industrial Area (MIA), Delhi, 12MLD; and the Integrated Industrial Estate (IIE) SIDCUL Pantnagar, 4.0 MLD. These plants were designed to produce treated effluent for non-potable reuse. Results showed that the integrated efficiency (IEa) of all CETPs was 10–20% larger than standard integrated efficiency (IEs), indicating the suitability of the technology, except for 12MLD at MIA CETP where the IEa was 20% lower than IEs, due to the absence of any biological unit in the process. Combined post-treatment of secondary effluent by coagulation, Ultrafiltration (UF), followed by ozonation for CETP SIDCUL Haridwar, was also conducted for its non-potable water reuse. This process was able to reduce Biochemical Oxygen Demand (BOD) by 77%, Chemical Oxygen Demand (COD) by 76%, turbidity by 96%, and Total Suspended Solids (TSS) by 100%. All these parameters confirmed the effluent standards for non-potable reuse. The color was reduced to 4.0 from 42.0 Pt-Co units by the exposure ozone concentration of 8.3 mg/L for up to 4.0 min on the treated water from SIDCUL CETP, which reduced the color by 90% and complied with reuse standards. Hence Combined post treatment by coagulation, UF followed Ozonation of secondary treated effluent could be a better option for the potable reuse of treated water in various domestic and industrial applications.

Tannery is one of the oldest industries in the world and is one of the fastest developing industries in India. It is one of the problematic industries in India which generate high quantum of wastewater with high TDS and toxicity due to chromium. Hence, discharge of tannery effluent is a very serious issue. Many conventional treatment processes has been carried out in these industry before the discharge of effluent. One of the most common treatment process applied is biological treatment process by activated sludge process and upflow anaerobic sludge blanket process. Due to the high cost of installation for this treatment process, in many of the small scale tannery industries in India, the wastewater treatment is carried out in common effluent treatment plant (CETP). In the present study the performance of CETP for tannery effluent in terms of Biological oxygen demand (BOD), Chemical oxygen demand (COD), Total suspended solids (TSS), Total dissolved solids (TDS), and by water tracer studies using Rhodamine. ETP showed a removal efficiency of BOD-66%, COD- 21%, TSS-21% and TDS-5%. The study revealed that ETP has to be redesigned based on the characteristics of influent wastewater in order to meet the Pollution Control Board prescribed standard limits for ETP.