Absar Ahmad Kazmi’s research while affiliated with Indian Institute of Technology Roorkee and other places

This work investigated the microbial community dynamics in ten full-scale cyclic technology-based sequencing batch reactors (SBR) based municipal wastewater treatment plants. In all the plants, pre-anoxic selectors are integrated with the main SBR aeration tanks, and the operation is controlled with dissolved oxygen (DO) conditions and oxygen uptake rates (OUR). All the cyclic technology based- SBR systems were capable of efficiently removing carbon (COD and Biochemical Oxygen Demand, BOD), total suspended solids (TSS), nitrogen (Total Nitrogen, TN), and phosphorus (Total Phosphorus, TP) from wastewater. The BOD removal was observed as 66%-98%, TN removal was 52%-89%, and TP removal was 41%-81% in the sewage treatment plants (STPs). The findings of microbial community analysis revealed that the numbers of Burkholderiales, Novosphingobium, Comamonas, and Rhodococcus were increased with the increase in C, N, and P removal efficiencies of all the treatment systems. Moreover, their relationships represented statistical significance. It was observed that with the dominance of Rhodococcus in WWTPs, the effluent N and P concentration was decreased, where r= 0.71, 0.67, and 0.69 and p= 0.02, 0.03, and 0.03, for effluent NO3-N, TN, and PO4-P, respectively. It was also observed that the increase in Nitrosomonas, Nitrospira_defluvii, and Novosphingobium in the STPs was found favorable for Enhanced biological phosphorus removal (EBPR) (r=0.9, p=0.0011; r=0.5, p=0.09; and r=0.7, p=0.04, respectively). Notwithstanding the absence of core polyphosphate accumulating organisms (PAOs), the microorganisms belonging to the order of Burkholderiales, Rhodocyclales, Pseudomonadales, Rhizobiales, Flavobacteriales, and Nitrospirales helped in favorable indirect biological phosphorus accumulation and the biological nitrogen removal.

This work investigated the role of operational conditions and typical functional microbes to maximize the nutrient removal efficiency of a pilot-scale sequencing batch reactor (SBR) system (100 m3/d) that treated municipal wastewater. The pilot system was operated in five phases, including start-up and four runs at variable cycle times (2.0, 1.5, 1.7, 2.0, and 3.0h) with an average readily biodegradable chemical oxygen demand (rbCOD) to chemical oxygen demand (COD) ratio of ∼15.3%. The best TN removal ‘ηmax’ of 75.6 ± 5.6% (TNinfluent= 27.5 ± 6.5 mg/L, TNeffluent ≤5.9 mg/L) and TP removal ‘pmax’ 77.9 ± 6.3% (TPinfluent= 3.8 ± 1.3 mg/L, TPeffluent ≤1.0 mg/L) along with the COD, biochemical oxygen demand (BOD), and total suspended solids (TSS) removal efficiencies of 87.3 ± 4.5%, 92.7 ± 2.8%, 92.0 ± 3.5%, respectively, were observed during run 3 (2h cycle) at settling/ total cycle times ratio (S/T) of 0.33 and recirculation/ total cycle times ratio (R/T) of 0.017 (6.4%), and operating DO of 0.5-2.5 mg/L. The denitrifying polyphosphate accumulating organisms ‘DPAOs’ of Burkholderia (17.0%), Rhodocyclales (6.1%), and Flavobacterium (8.7%) classes, and Nitrifiers of Nitrospira (5.4%) and Nitrosomonas (5.4%) classes were dominant in accomplishing simultaneous nitrification, denitrification, and phosphorus removal (SND-PR) in the pilot system.

Simultaneous biological nutrient removal (SBNR) using an anaerobic-anoxic-oxic phase is the key feature of advanced wastewater treatment plants (WWTPs). Removing ammonia, total nitrogen, and phosphorus concurrently with organic matter and suspended solids from wastewater is essential to meeting stringent effluent discharge standards via SBNR in WWTPs. More insight into the mechanisms of SBNR, i.e., simultaneous nitrification-denitrification (SND) and enhanced biological phosphorus removal (EBPR) processes, the intracellular carbon reserves, i.e., polyhydroxyalkanoates (PHA) and specifically poly-β-hydroxybutyrates (PHB), will play a critical role in nutrients removal and resource recovery in WWTPs. Volatile fatty acids (VFA) in wastewater are the preferable source of PHA formation. However, municipal wastewater could not supply sufficient VFA fractions owing to short sewer lines; therefore, developing pre-fermentation chambers and other technological integration in the WWTPs can play an effective role in VFA production from raw sewage, resulting in the effective formation of PHA. On the other hand, PHA is a value-added biochemical, i.e., a potential substitute for fossil fuel plastics. WWTPs complying with SBNR are the bio-refineries for PHA (bioplastic precursors) production using diverse microbial populations. This review enlightens three dimensions of progressive systems and engineering-based viewpoints: (i) Increasing the SBNR by optimizing operational conditions subject to the substrate storage mechanisms of treatment systems; (ii) Technical solutions to enhance the VFA availability in sewage in WWTPs to achieve effective SBNR; and (iii) production of PHB (PHA) in WWTPs.

The present study assessed a mechanical biological treatment (MBT) based solid waste treatment and disposal (SWTD) facility of an Indian Municipality. The non-biodegradable and the biodegradable fractions are separated from the mixed waste by trommel screens. The biodegradable fraction is used to make compost. The nonbiodegradable fraction is recovered as a segregated combustible fraction (SCF)/solid recovered fuel (SRF), whereas the inert fraction is disposed of at the dump site. The compost produced from the biodegradable fraction had a lower percentage of total potash and organic carbon than the prescribed standards.The SCF/SRF of the trommel screen of 80mm and 32mm openings were found to have 4672.94 and 2728.26kcal/Kg energy content, 60.43 and 57.69% volatile content, 3.31 and 7.80% ash content, and 6.81 and 4.38% fixed carbon content. The recovered SCF/SRF meets the fuel specification prescribed by the Indian Solid Waste Management (SWM) Rules 2016. However, the facility needs to address the issues and challenges related to the implementation and operation. The outcomes and learnings of the study are guiding sources for the researchers, waste treatment and disposal plant operators, designers, and policymakers of developing countries.