A critical review on slaughterhouse waste management and framing sustainable practices in managing slaughterhouse waste in India.

Global meat consumption is on a rise with around 253 million metric tons of meat produced globally in the year 2020. Because of the rise in population and change in food preferences, meat consumption trend is likely to continue. Meat production by animal slaughtering increases the slaughterhouse wastes in the form of both solid and liquid wastes. Although various technologies for slaughterhouse waste management are available in developed countries, the effective utilization of slaughterhouse waste management is still missing in developing countries like India. India plays an active role in the meat export business globally and stood 2nd in the world with a total export valuation of 2.89 billion US $ in the year 2020. In this context, this study presents a critical overview of the current technological advancements in the global slaughterhouse waste management including utilization of by-products and further, the prevailing slaughterhouse waste management of India is discussed. Finally, a sustainable slaughterhouse waste management strategy emphasizing circular economy and regulations improvements have been suggested for India to compete in this sector at global scale.

Process performance and reuse potential of a decentralized wastewater treatment system.

The paper describes briefly the process performance and the reuse potential of a laboratory scale wastewater treatment system. The treatment involves enhanced primary treatment of Vellore Institute of Technology (VIT) campus sewage using ferric chloride as a coagulant, anaerobic digestion of coagulated organics, and biofilm aerobic process. The treated effluent after disinfection (using sunlight and chlorine) was used for irrigation of Tagetes erecta (marigold) plants and the plant growth parameters were evaluated for a life span of 3 months. In the primary treatment, an optimum ferric chloride dose of 30 mg/L could remove turbidity, chemical oxygen demand (COD), biochemical oxygen demand (BOD), and bacterial count (Escherichia coli) of 69%, 60%, 77%, and 55%, respectively. The coagulated organics could digest in a 25 L anaerobic reactor effectively with methane content in biogas varied between 50 and 60% and enhanced volatile suspended solids (VSS) reduction up to 70%. Sunlight based photo-oxidation followed chlorine disinfection saved 50% of the chlorine dose required for disinfection and treated effluent was fit for reuse. The results of growth parameters for Tagetes erecta plants indicate that anaerobically digested sludge is an excellent soil conditioner cum nutrient supplier. The results of this study exhibit a promising reuse potential of a decentralized wastewater treatment system and needs to be promoted for field scale applications.

Unprecedented development of anammox in presence of organic carbon using seed biomass from a tannery Common Effluent Treatment Plant (CETP).

This work describes development of a microbial consortium dominant in anammox in presence of organic carbon (available through cell lyses) by employing simple sequencing batch operation in 23 cycles exceeding 400days. Seed biomass from a tannery Common Effluent Treatment Plant (CETP) was enriched for anammox and attained maximum removals of NH4-N (95%) and NO2-N (98%). The anammox was confirmed by nitrogen mass balance in a controlled batch experiment and by DNA extraction-PCR-agarose gel electrophoresis. The effective anammox followed first order reaction kinetics with rate constant of 0.0141/h and half-saturation constant of 10.6mg/L. Evidence for coexistence of denitrification (99% NO2-N removal) and anammox (57.8% NH4-N removal) was demonstrated. This study opens-up possible application of microbial consortium dominant in anammox for simultaneous removal of ammonia and organic carbon from wastewaters.

Effect of potential electron acceptors on anoxic ammonia oxidation in the presence of organic carbon.

A novel route of anoxic ammonia removal in the presence of organic carbon was identified recently from ecosystems contaminated with ammonia. Sequencing batch reactor (SBR) studies were carried out in anoxic condition at oxidation-reduction potential varied from -185 to -275 mV for anoxic ammonia oxidation with adapted biomass (mixed culture). SBR studies were carried out in absence and in the presence of externally added organic carbon and/or in the presence of inorganic electron acceptors like NO2(-), NO3(-) and SO4(2-). The results showed anoxic ammonia oxidation to nitrate (in contrast to reported anammox process) in the presence of organic carbon available through endogenous respiration whereas anoxic ammonia oxidation was effective in the presence of externally added organic compound for nitrogen removal. The presence of externally added inorganic electron acceptors like NO2(-), NO3(-) and SO4(2-) was effective in anoxic ammonia oxidation, but failed to follow the reported anammox reaction's stoichiometry in nitrogen removal in the presence of organic carbon. However, the presence of NO2(-) affected best in total nitrogen removal compared to other electron acceptors and maximum ammonia removal rate was 100 mg NH4(+)/g MLVSS/d. Based on the results, it is possible to suggest that rate of anoxic ammonia oxidation depends up on the respiration activities of mixed culture involving organic carbon, NO2(-), NO3(-) and SO4(2-). The process shows possibilities of new pathways of ammonia oxidation in organic contaminated sediments and/or wastewater in anoxic conditions.

Development of the Sulphidogenesis Cum Ammonia Removal Process for treatment of tannery effluent.

The present paper describes the development of Sulphidogenesis Cum Ammonia Removal Process (SCARP) with a simple sulphide inhibition control. The process was developed using synthetic effluent and its application for treatment of primary treated tannery effluent was demonstrated. This paper also discusses the effects of HRT and loading rates. The developed SCARP could treat efficiently the primary treated tannery effluent with influent concentrations of COD, SO4(2-) and NH4+ equal to 3,900 mg/L, 3,000 mg/L and 300 mg/L, respectively. An HRT of 10.5 hours was found to be adequate for COD, NH4-N and SO4(2-) loading rates of 8.9 kg COD/m3/d, 0.68 kg NH4+/m3/d, 6.84 kg SO4(2-)/m3/d, respectively. The overall removal efficiencies of COD, NH4-N and SO4(2-) for the above loading rates were in the ranges of 90.8-91.8%, 84-88.3% and 64.2-70.2%, respectively. The system performance was satisfactory for different loading rates and low COD/SO4(2-) ratios. The developed SCARP has good potential as a cost effective alternative treatment process to existing extended aeration process with nitrification-denitrification for the secondary treatment of tannery effluent.

Development of an ecologically sustainable wastewater treatment system.

The present study aimed mainly for the development of a wastewater treatment system incorporating enhanced primary treatment, anaerobic digestion of coagulated organics, biofilm aerobic process for the removal of soluble organics and disinfection of treated water. An attempt was also made to study the reuse potential of treated water for irrigation and use of digested sludge as soil conditioner by growing marigold plants. Ferric chloride dose of 30 mg/l was found to be the optimum dose for enhanced primary treatment with removals of COD and BOD to the extent of 60% and 77%, respectively. Efficient anaerobic digestion of ferric coagulated sludge was performed at 7 days hydraulic retention time (HRT). Upflow aerobic fixed film reactor (UAFFR) was very efficient in removals of COD/BOD in the organic loading rate (OLR) range of 0.25 to 3 kg COD/m(3)/day with COD and BOD removals in the range 65-90 and 82-96, respectively. Photo-oxidation followed by disinfection saved 50% of chlorine dose required for disinfection of treated effluent and treated water was found to be suitable for irrigation. The result also indicated that anaerobically digested sludge may be an excellent soil conditioner. From the results of this study, it is possible to conclude that the developed wastewater treatment system is an attractive ecologically sustainable alternative for sewage treatment from institutional/industrial/residential campuses.

Development of enhanced sulphidogenesis process for the treatment of wastewater having low COD/SO(4)(2-) ratio.

An upflow hybrid sulphidogenesis reactor of 1.75 L volume was developed (at oxidation-reduction potential (ORP)=-225+/-25 mV) using flocculent extended aeration process sludge (selected based on screening study at COD/SO(4)(2-) ratio=1) for enhanced sulphidogenesis and COD removal. The reactor was subjected to various loading rate studies at a hydraulic retention time (HRT) of 1 day with COD/SO(4)(2-) ratio of 1.3. At loading rate of 2.5 kg COD/(m(3)day), excellent performance with more than 97% removal of sulphate was achieved within bottom 40% volume of the reactor. At a higher loading rate of 3.75 kg COD/(m(3)day), there was a decrease in both sulphate (70-75%) and COD (50%) removal efficiencies. A controlled and continuous air injection (0.19 L/(L min)) given at 40% volume of the reactor affected sulphide oxidation inside the reactor and enhanced the sulphate reduction in the reactor. The specific sulphate reduction capacity of mixed culture drawn from the bottom part of the reactor was 0.35 kg SO(4)(2-)/(kg VSS day). The results of this study showed that enhanced sulphidogenesis with sulphide inhibition control can maintain sulphate-reducing bacteria (SRB) in anaerobic reactor at low COD/SO(4)(2-) ratios between 1 and 2, with efficient simultaneous removal of COD and SO(4)(2-). The sulphide generated in the system can be recovered as elemental sulphur and/or oxidized back to sulphate.

Anaerobic ammonia removal in presence of organic matter: a novel route.

This study describes the feasibility of anaerobic ammonia removal process in presence of organic matter. Different sources of biomass collected from diverse eco-systems containing ammonia and organic matter (OM) were screened for potential anaerobic ammonia removal. Sequential batch studies confirmed the possibility of anaerobic ammonia removal in presence of OM, but ammonia was oxidized anoxically to nitrate (at oxidation reduction potential; ORP=-248+/-25 mV) by an unknown mechanism unlike in the reported anammox process. The oxygen required for oxidation of ammonia might have been generated through catalase enzymatic activity of facultative anaerobes in mixed culture. The oxygen generation possibility by catalase enzyme route was demonstrated. Among the inorganic electron acceptors (NO(2)(-), NO(3)(-) and SO(4)(2-)) studied, NO(2)(-) was found to be most effective in total nitrogen removal. Denitrification by the developed culture was much effective and faster compared to ammonia oxidation. The results of this study show that anaerobic ammonia removal is feasible in presence of OM. The novel nitrogen removal route is hypothesized as enzymatic anoxic oxidation of NH(4)(+) to NO(3)(-), followed by denitrification via autotrophic and/or heterotrophic routes. The results of batch study were confirmed in continuous reactor operation.

Preliminary study of physico-chemical treatment options for hospital wastewater.

Hospital effluents are loaded with pathogenic microorganisms, partially metabolized pharmaceutical substances, radioactive elements, and other toxic substances. Such effluents if not treated properly can damage the natural environment and create a biological imbalance. This paper points out the areas of concern for hospital wastewater disposal and reports the findings of a limited physico-chemical study of treatment options for hospital effluents conducted at Christian Medical College and Hospital, Vellore, Tamil Nadu. The effluent collected was checked for conventional parameters and subjected to coagulation experiments. The raw and settled effluents were coagulated with FeCl(3), filtered and disinfected. Physico-chemical treatment seems to be an attractive option for the cost-effective disposal of hospital effluents. The results of this study call for further detailed study in this area.

Reuse of textile effluent treatment plant sludge in building materials.

This study examines the potential reuse of textile effluent treatment plant (ETP) sludge in building materials. The physico-chemical and engineering properties of a composite textile sludge sample from the southern part of India have been studied. The tests were conducted as per Bureau of Indian Standards (BIS) specification codes to evaluate the suitability of the sludge for structural and non-structural application by partial replacement of up to 30% of cement. The cement-sludge samples failed to meet the required strength for structural applications. The strength and other properties met the Bureau of Indian Standards for non-structural materials such as flooring tiles, solid and pavement blocks, and bricks. Results generally meet most ASTM standards for non-structural materials, except that the sludge-amended bricks do not meet the Grade NW brick standard. It is concluded that the substitution of textile ETP sludge for cement, up to a maximum of 30%, may be possible in the manufacturing of non-structural building materials. Detailed leachability and economic feasibility studies need to be carried out as the next step of research.

An improved method for defluoridation.

Fluoride is a naturally occurring toxic mineral present in drinking water and the root cause of many diseases and disorders. Present international drinking water standard set by World Health Organisation (WHO) for fluoride is 1.5 ppm. In order to find the wide spread concentration of fluoride in drinking water of fluoride contaminated aquifer, 30 bore well water samples have been collected from different villages of Natrampalli Union which comes under Tiruvannamalai Circle, Tamil Nadu, India. In the present work, an attempt to remove fluoride by the use of coagulant, Poly Aluminium Chloride (PAC) was made and is compared with the most common existing technique "Nalgonda Technique" where there was a reversible reaction. The coagulant used in Nalgonda technique is Alum [(Al2SO4)3]. Results of the present work show that Poly Aluminium Chloride (PAC) can be an effective coagulant for the removal of fluoride from water with a higher removal efficiency of about 75 - 85% in less detention time and also observed that the fluoride removal was dependent on initial fluoride concentration and dose of coagulants.