Effectiveness of breakpoint chlorination and rechlorination on nitrified chloraminated water

Chloramine is used as a secondary disinfectant in water distributions system (WDS). However, nitrification is a major concern involved in the chloraminated WDS as it leads to the accelerated decay of chloramines. After the onset of nitrification, breakpoint chlorination followed by rechlorination is generally practiced in WDS to reinstate chloramine residuals in the WDS. In this study, two different control strategies re-chlorination and breakpoint chlorination followed rechloramination were applied on the severely nitrified water collected from the laboratory-scale reactor system. Results showed that breakpoint chlorination followed by rechloramination is highly stable as the chloramine residual was maintained up to 300 hours and is highly effective than rechlorination alone as it could maintain residue only up to 50 hours even with repeated re-dosing

Intellectual Property Right on Basmati Rice: Current Scenario and Evidences of Origin, Diversity, Cultivation and Use Values of Basmati Rice in Nepal

Basmati rice, also called the king/prince of rice landraces has very special values in Nepalese society as well as in other countries of Indian Subcontinent. With the objectives of collecting, analyzing and documenting Basmati related information in Nepal, we visited different sites; carried out key informant surveys; organized focus group discussions, online interaction and discussion meetings; requested all relevant offices/ persons/ stakeholders through phone, website, and letter to share information; organized high level official meeting, and Basmati rice expert meeting; documented video documentary and did online as well as library search. Because of its high market value at global level, many countries and organizations have been attempting to get intellectual property rights (mainly patent and geographical indication tag) on Basmati rice. India applied for GI tag to Basmati rice in the European Union (EU) in July 2018, and Nepal submitted opposition letter along with proofs and evidences of origin, diversity, cultivation and use values of Basmati rice on 9 December 2020. A total 133 Basmati type rice landraces are grown in 60 districts of Nepal. Basmati rice is traditionally grown, sold, and consumed in geographically localized areas of Nepal since ancient time. International and national scientists have defined lower altitude of Nepal as one of the centers of origin of Basmati rice. Many Nepalese basmati rice landraces have been characterized and evaluated using morphological traits, isozymes and DNA markers. Four basmati type of rice landraces have been registered in National Seed Board. Many community seed banks have maintained different types of Basmati rice landraces. National Agriculture Genetic Resources Center and International genebanks have collected more than 80 and conserved 68 basmati landraces. Basmati rice landraces have geo-linked traits. The historical culture of production, consumption and marketing of native basmati rice in Nepal should always be favored by both national and international rules and regulations. Nepal has ample and valid evidences to get geographical indication (GI) right on Basmati rice

Agrobiodiversity and Its Conservation in Nepal

Nepal is a part of the world\u27s biodiversity hotspot and ranks the 49th in the world for biodiversity. Agrobiodiversity and its conservation status were studied through literature review, field survey, key informant survey and focus group discussion. Results of field implementation of some good practices and action research were also documented. Among 24,300 total species in the country, 28% are agricultural genetic resources (AGRs), termed as agrobiodiversity. Agrobiodiversity has six components (crops, forages, livestock, aquatic, insects and microorganisms) and four sub-components (domesticated, semi-domesticated, wild relatives and wild edible) in Nepal. Agrobiodiversity on each component exists at agroecosystem, species, variety/breed/biotype/race/strain, genotype and allele levels, within an altitude range from 60 to 5,000 masl. There are 12 agroecosystems supporting 1026 species under crop component, 510 under forage, 35 under livestock, 250 under the aquatic animal, 17 under aquatic plant, 3,500 under insect and 800 under microorganism. An estimated loss of agrobiodiversity is 40%, however, farmers have reported up to 100% loss of AGRs in some areas for a particular species. Conservation of agrobiodiversity has been initiated since 1986. Four strategies namely ex-situ, on-farm, in-situ and breeding have been adopted for conservation and sustainable utilization of AGRs. Eighty good practices including process, methods and actions for managing agrobiodiversity have been in practice and these practices come under five conservation components (sensitization, method and approach, accelerator, value and enabling environment). Within the country, 18,765 accessions of AGRs have been conserved in different kinds of banks. A total of 24,683 accessions of Nepalese crops, forages and microbes have been conserved in different International and foreign genebanks. Some collections are conserved as safety duplication and safety backup in different CGIARs\u27 banks and World Seed Vault, Korea. Two global databases (GENESYS and EURISCO) have maintained 19,200 Nepalese accessions. Geographical Information System, Climate Analog Tool and biotechnological tools have been applied for better managing AGRs. Many stakeholders need to further concentrate on the conservation and utilization of AGRs. Global marketing of some native AGRs is necessary for sustaining agriculture and attracting young generations as well as conserving them through use

An integrated kinetic model for organic and nutrient removal by duckweed-based wastewater treatment (DUBWAT) system

This study was conducted to investigate the efficiency of duckweed (Lemna gibba) in treating a domestic wastewater and to develop an integrated kinetic model for organic and nutrient removal by duckweed-based wastewater treatment (DUBWAT) system. Four pilot-scale DUBWAT units, made of concrete blocks, were operated under ambient conditions (temperatures 30-36 °C), different hydraulic retention times (t), organic loading rates (OLR) and stocking densities (SD). The maximum COD, BOD5, NH3-N, TN and TSS removal efficiencies of 84, 88, 68, 58 and 87%, respectively, were found at optimum operating conditions of t of 10 days, OLR of 50 kgCOD/(ha-d) and SD of 0.5 kg/m2. The nitrogen uptake rate by duckweed was found to be 0.62 g-N/(m2-d). An integrated kinetic model consisting of t, OLR, SD and temperature was developed for the DUBWAT system and validated satisfactorily with data obtained from the literatures

Effect of Different Disinfectants on Grey Water Quality during Storage

Grey water offers potential to save large amount of potable water resources. However, grey water can only be stored for up to 24 hours in most parts of the world because of the fast deterioration in quality due to bacterial growth. Several physical, biological and chemical treatment methods or combination of them can be employed to safely increase the retention time. In this study, grey water sample collected from a typical urban house in Western Australia was used to investigate the effectiveness of physical, chemical and combination of them to treat for stor-ing longer time. For chemical treatment, chlorine, chloramine and hydrogen peroxide were assessed whereas for physical treatment, grey water samples were filtered through 11μm filter paper to remove large suspended solids. Chloramine was found to be effective for storing longer time without combination of physical treatment. It was noted that organic matter present in grey water induces a greater chlorine demand and prevent proper disinfection. Chlorine was found to be highly reactive with impurities found in grey water, so removal of these impurities is es-sential through filtration. Hydrogen peroxide was ineffective at low doses and was the weakest of the three disinfec-tants

Comparative study of ground water treatment plants sludges to remove phosphorous from wastewater

Alum- and iron-based sludge obtained from water treatment plant produced during a unit treatment process (coagulation and flocculation) have been widely tested as a low-cost adsorbent to remove phosphorous (P) from wastewater. However, the effectiveness of iron-based sludge generated from the oxidation of iron which naturally occurs in the ground water has not been investigated. Moreover, influences of dominant metals ions comprised in the treatment plants sludges on P adsorption capacity and rate from wastewater are not yet known. This study, therefore, employed four different groundwater treatment plants sludges iron-based (from the oxidation of iron) and alum-based (from coagulation and flocculation process) to determine their P adsorption capacities and adsorption rates from the synthetic wastewater (SWW) and secondary effluent wastewater (SEWW). Although metals ions concentrations were the highest in the iron-based sludge amongst the sludge used in this study, it appeared to have the lowest P adsorption capacity and adsorption rate. A good correlation between aluminium to iron mass ratio and adsorption capacity for both types of waters were noted. However, a poor relation between aluminium to iron mass ratio and adsorption rates for the SEWW was observed. Further, the tested sludges were found to have a better P removal efficiency and adsorption capacity from the SEWW than from the SWW. Thus, this study demonstrates the ground water treatment plants sludges could be a low cost and effective adsorbent in removing P from wastewater

Wider presence of accelerated chemical chloramine decay in severely nitrifying conditions

Popularity of chloramine has been dampened by nitrification, which is believed to highly accelerate chloramine decay. This can seriously compromise the primary goal of using chloramine as a secondary disinfectant. Our previous laboratory-scale studies showed that highly accelerated chemical decay of chloramine was caused by soluble microbial products (SMPs) released by microbes under severely nitrifying conditions. To understand whether a similar phenomenon exists in full-scale distribution systems, samples were collected from four full-scale systems supplied from different water sources and have been compared with results obtained from laboratory-scale systems. The results verified that the acceleration typical in severely nitrified water is common in full-scale chloraminated systems under severely nitrifying conditions

Influence of treatment processes and disinfectants on bacterial community compositions and opportunistic pathogens in a full-scale recycled water distribution system

In this study, for the first time, a recycled water distribution system was analysed in which the inorganic nitrogen content in the recycled water was substantially minimised (85%) having minimal disinfection abilities. The majority of the bacterial communities were proteobacteria comprising alpha-, beta-, and gamma-proteobacteria, similar to the drinking water distribution system. The gene copy numbers of total bacterial 16S ribosomal ribonucleic acid (16S rRNA) and opportunistic pathogens (OPs) were significantly decreased after the chlorination, but their populations increased with the decrease of total chlorine residual level in the distribution system. The total bacterial 16S rRNA significantly correlated with Legionella spp., Mycobacterium spp., and Pseudomonas aeruginosa. Similarly, significant correlations existed between OPs (particularly Legionella spp. and Pseudomonas aeruginosa) and iron-oxidising, manganese-oxidising, and sulphate-reducing bacterial genera. The detection of several OPs in the absence of E. coli shows that the traditional indicator used for compliance monitoring may not accurately represent the microbial water quality. This study suggests monochloramine as an alternative secondary disinfectant

Effectiveness of breakpoint chlorination to reduce accelerated chemical chloramine decay in severely nitrified bulk waters

Rectifying the accelerated chloramine decay after the onset of nitrification is a major challenge for water utilities that employ chloramine as a disinfectant. Recently, the evidence of soluble microbial products (SMPs) accelerating chloramine decay beyond traditionally known means was reported. After the onset of nitrification, with an intention to inactivate nitrifying bacteria and thus maintaining disinfectant residuals, breakpoint chlorination followed by re-chloramination is usually practiced by water utilities. However, what actually breakpoint chlorination does beyond known effects is not known, especially in light of the new finding of SMPs. In this study, experiments were conducted using severely nitrified chloraminated water samples (chloramine residuals 0.1mgNL-1 and an order of magnitude higher chloramine decay rate compared to normal decay) obtained from two laboratory scale systems operated by feeding natural organic matter (NOM) containing and NOM free waters. Results showed that the accelerated decay of chloramine as a result of SMPs can be eliminated by spiking higher free chlorine residuals (about 0.92±0.03 to 1.16±0.12mgCl2L-1) than the stoichiometric requirement for breakpoint chlorination and nitrite oxidation. Further, accelerated initial chlorine decay showed chlorine preferentially reacts with nitrite and ammonia before destroying SMPs. This study, clearly demonstrated there is an additional demand from SMPs that needs to be satisfied to effectively recover disinfection residuals in subsequent re-chloramination

Microbial community changes with decaying chloramine residuals in a lab-scale system

When chloramine is used as a disinfectant, managing an acceptable "residual" throughout the water distribution systems particularly once nitrification has set in is challenging. Managing chloramine decay prior to the onset of nitrification through effective control strategies is important and to-date the strategies developed around nitrification has been ineffective. This study aimed at developing a more holistic knowledge on how decaying chloramine and nitrification metabolites impact microbial communities in chloraminated systems. Five lab-scale reactors (connected in series) were operated to simulate a full-scale chloraminated distribution system. Culture independent techniques (cloning and qPCR) were used to characterise and quantify the mixed microbial communities in reactors maintaining a residual of high to low (2.18-0.03mg/L). The study for the first time associates chloramine residuals and nitrification metabolites to different microbial communities. Bacterial classes Solibacteres, Nitrospira, Sphingobacteria and Betaproteobacteria dominated at low chloramine residuals whereas Actinobacteria and Gammaproteobacteria dominated at higher chloramine residuals. Prior to the onset of nitrification bacterial genera Pseudomonas, Methylobacterium and Sphingomonas were found to be dominant and Sphingomonas in particular increased with the onset of nitrification. Nitrosomonas urea, oligotropha, and two other novel ammonia-oxidizing bacteria were detected once the chloramine residuals had dropped below 0.65mg/L. Additionally nitrification alone failed to explain chloramine decay rates observed in these reactors. The finding of this study is expected to re-direct the focus from nitrifiers to heterotrophic bacteria, which the authors believe could hold the key towards developing a control strategy that would enable better management of chloramine residuals