Abstract
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.
Highlights
Approximately 80 countries and 40% of the world’s population are facing water scarcity, and the demand for water doubles every 2 decades (Aziz et al, 2008)
Regulating agencies have observed that common effluent treatment plants (CETPs) do not discharge satisfactory effluent for reuse, because of technological/process design limitations and the massive fluctuation in the organic load of primary treated effluent from industries, which hampers the biological activity of aeration tanks due to varied pH and other operational parameters
Treatment Scheme of Common Effluent Treatment Plants 55 Million Liters Per Day at Industrial Model Township Manesar, Gurgaon The integrated CETPs (25 Million Liters per day (MLD) and 30 MLD) treatment system involved raw effluent collection followed by preliminary treatment (Screening, Grit Removal and, Equalization), Physico-chemical treatment (Clariflocculator for 25 MLD, and separate flocculators and clarifiers for 30 MLD), secondary biological treatment (Extended Aeration), and tertiary treatment by Dual Media Filtration (DMF) (Figure 3)
Summary
Approximately 80 countries and 40% of the world’s population are facing water scarcity, and the demand for water doubles every 2 decades (Aziz et al, 2008). Small to medium scale industries often do not comply with these stringent reuse standards due to well-documented reasons, such as a lack of footprint assessment, specialized manpower, limited financial assets/funds, and high capital cost (Pathe et al, 2004) These problems could be reduced by the collective treatment of effluents from a large number of small-scale facilities at a single site where the effluent from each undergoes treatment (Padalkar, Kaur, and Kumar, 2016). Regulating agencies have observed that CETPs do not discharge satisfactory effluent for reuse, because of technological/process design limitations and the massive fluctuation in the organic load of primary treated effluent from industries, which hampers the biological activity of aeration tanks due to varied pH and other operational parameters.
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