Girish R. Pophali

Optimal selection of full scale tannery effluent treatment alternative using integrated AHP and GRA approach

The selection of optimal wastewater treatment alternative involves multiple objectives and/or criteria and hierarchy process. This study integrates analytical hierarchy process (AHP) and grey relation analysis (GRA) for optimal selection of full scale tannery effluent treatment plants. For this purpose, seven tanneries and their effluent treatment facilities are studied in detail in Southern India. The objective hierarchy criterion is considered based on three factors; economic, technical, and administrative, each ofwhich againinvolves hierarchy of indices. A realistic treatment alternative selection is obtained since all the data used is on actual basis.The biggest advantage of this approach is that it provides the information regarding the scope for further improvement in existing treatment options. The study indicates that the AHP and grey relation analysisare powerful tools that can be used for implementation of appropriate wastewater treatment technology.

Treatment of refractory organics from membrane rejects using ozonation

The reject water or retentate generated from membrane application for recovery of water from tannery wastewater treatment contains certain refractory organics. These refractory organics are present in substantial quantity in the condensate of reject water also. Hence the treatment of rejects using conventional methods is rather difficult. In this paper, an attempt has been made to treat the reject water from the reverse osmosis (RO) and nano filtration (NF) operation on tannery wastewater using ozonation treatment technique. Ozonation studies on RO and NF rejects indicate that ozone dose of 80 and 100mg/min for 60 and 70 min contact time achieves 59 and 78% chemical oxygen demand (COD) reduction, respectively. The mass balance in ozone indicates the ozone consumption for RO and NF rejects varies from 2.4 to 3.4 and 2.8 to 4.5 g/g of COD removed respectively. The results suggest that ozonation of RO and NF rejects would significantly reduce the refractory organic pollutant loading into the environment from wastewater reuse facility.

Treatment of refractory nano-filtration reject from a tannery using Pd-catalyzed wet air oxidation

We attempted catalytic wet air oxidation (CWAO) of nanofiltration (NF)-reject using Pd based catalyst viz., Pd/activated charcoal (AC) and PdCl2 with the objective of degradation of refractory organic pollutants. Refractory organic pollutants in NF-reject before and after WAO and CWAO were confirmed by GC-MS analysis. Experiments were conducted to investigate the effects of temperature, catalyst dosage and air partial pressure on the rate of removal of total organic carbon (TOC). The reaction kinetics can be conveniently described by considering two-stage first order kinetics. The use of Pd/AC afforded 85% TOC removal, the corresponding rate constant (k) was 2.90 ± 0.075 × 10(-3)min(-1) (Pd/AC, 100mg/L; T, 473.15K; Pair, 0.69 MPa). On the other hand, 75% TOC was removed with k=2.31 ± 0.075 × 10(-3)min(-1) using Pd(2+) catalyst (Pd(2+), 16.66 mg/L; T, 473.15K; Pair, 0.69 MPa). The observed rate of mineralization under Pd-catalyzed conditions was significantly higher than that of the uncatalyzed oxidation (41%) under the similar experimental conditions. Catalyst stability experiments were performed and TEM, SEM, XRD, Raman and XPS characterization data collected. Despite some morphological transformation of support, Pd catalyst was stable under CWAO conditions.

Development of a novel circular secondary clarifier for improving solids liquid separation in wastewater treatment.

A novel circular secondary clarifier was developed to obviate the shortcomings of conventional clarifiers. The novel clarifier provides natural flocculation, which occurs as a result of hydraulic energy dissipation and the formation of sludge cloud referred to as plume. The efficiency of the clarifier depends on the stability of the plume, which in turn depends on the velocity gradient. For natural flocculation to occur, a velocity gradient of 10 to 15 s(-1) was found to be favorable. This velocity also keeps the plume-rise well below the free-surface. The mean particle size of mixed liquor suspended solids increases from 41 to 83 microm in the plume, which indicates agglomeration of particles and confirms that natural flocculation is occurring within the plume. The hydraulic improvement achieved by improving inlet design dissipates hydraulic energy, uniformly distributes flow, minimizes sludge blanket disturbances, and promote flocculation. The improved clarifier operates at 1-h hydraulic retention time.

Biomimetic lipophilic activated carbon for enhanced removal of triclosan from water

Triclosan, an antimicrobial micro-pollutant with a high bio-accumulation potential represented by its high octanol-water partition coefficient (log Kow) of 4.76 is commonly encountered in water and wastewater worldwide. The present study focuses on biomimetic surface modification of commercial activated carbon (PAC) with long chain fatty acid namely docosahexaenoic acid (DHA) resulting in enhanced affinity for the hydrophobic micro-pollutant; triclosan (TCS). The sorption process of the resulting modified lipophilic carbon (PACM) was investigated for the effect of various experimental conditions. The Freundlich isotherm and pseudo-second-order kinetic models had a better fit. PACM exhibited the maximum adsorption capacity of 395.2 mg g-1 in contrast to 71.5 mg g-1 obtained for PAC. The surface morphology in terms of surface area, surface acidity, pore size, contact angle, etc. and were also evaluated. The contact angle of 134.3° obtained for PACM confirmed its highly hydrophobic nature. The efficacy of PACM was also evaluated using real-world secondary treated effluent containing triclosan confirming its applicability for tertiary treatment of wastewater. The study established that the biomimetic approach of creating lipid-like sites on the carbon surface results in the enhanced removal of lipophilic micro-pollutants. It can also be utilized for the removal and recovery of a wide variety of other organic micro-pollutants.

Application of the NaWaTech Safety and O&M Planning Approach Re-Use Oriented Wastewater Treatment Lines at the Ordnance Factory Ambajhari, Nagpur, India

Not only due to a lack of infrastructure such as treatment plants, but also because the majority of existing treatment plants are showing poor or very poor operating conditions and fail to meet their performance targets, India faces increasing water shortage and degradation of fresh water resources. The paper gives an overview on the methodology of a safety and O&M (operation and maintenance) planning approach developed and implemented for supporting sustainable long-term operation of wastewater treatment systems. The implementation of the methodology is shown for the pilot installation at Ordnance Factory Ambajhari, Nagpur, India. At this site, two treatment lines have been installed: Line 1 is designed for 100 m3/day and comprises anaerobic pre-treatment, a vertical upflow constructed wetland, followed by a disinfection step, line 2 designed for 8 m3/day is a 2-stage French Reed Bed system. The effluent of the French Reed Bed system is used for irrigation of a Short Rotation Plantation. The safety and O&M planning approach was used to identify critical O&M tasks, develop site-specific trainings of operators as well as a basis to develop the O&M manual and materials for operators (such as check-lists, etc.).