Identification and characterisation of chloramine decaying proteins and control of impact in chloraminated systems

Chloramine is the second most popular disinfectant behind chlorine used in water distribution systems. The main advantages of using chloramine over chlorine are; it provides a longer lasting disinfectant residual and forms a less amount of the regulated halogenated disinfection by-products. However, at times, microbial chloramine decay can overwhelm stability and is identified as one of the serious problems that needs addressing. One of the mechanisms of microbial chloramine decay is by production of soluble microbial products (SMP), which substantially affects the chloramine decay. The SMP are usually composed of proteins, polysaccharides, humic acids, fulvic acids, nucleic acids, enzymes and structural compounds, but it was suspected that the chloramine decaying SMP could be protein(s) due to the catalytic effect that was noted in the samples. It was noted in soluble form in water after the onset of nitrification in a chloraminated system. When the SMP was filtered out of the water and was run on the SDS page to identify the compound 25 different proteins were seen with weaker signals. Therefore, the identity of chloramine decaying soluble microbial products (SMP), which microbes produce them and how to control them are not known. If SMP was produced by nitrifiers and since nitrifiers could be inhibited by higher organic carbon levels when changing dissolved organic carbon (DOC) level in the water, it could alter the production of chloramine decaying SMP. Therefore, batch rechloramination tests were conducted for reactor sets with variable DOC levels to understand their effect on the impact of SMP. The results revealed as the highest production of SMP had been stimulated with low DOC level (0-1mg-C.L-1) compared to other DOC levels (2-3, 4-5 and 7-8 mg-C.L-1). To recognize microbial community variations with the impression of identifying CDP producing micro-organisms, microbial community analysis was also carried out in the same reactor sets. Significant differences in bacterial types against DOC variations could not be detected. However, some of the bacterial types such as Micobacterium, AOB, Bradyrhizobium sp., Methylobacterium and family Sphingomonadaceae recognized in this study are known to produce extracellular polymeric substances (EPS). My early work has identified that SMP are proteins; hence, named as chloramine decaying proteins (CDP). In Relation to the context of these experiments, the proteins consisting within EPS can be considered as CDP. Questioning if nitrifiers always produce CDP, two nitrified reactors - one with chloramine (chloraminated reactor) and the other with ammonia (ammoniated reactor) - were operated using nutrient added Milli-Q water as the feed water in a way nitrification occurs within the reactor. MilliQ was selected since it produced the highest concentration of CDP. It was expected that CDP could be easily separated amongst 25 previously found proteins. Therefore, nitrified bulk water and biofilm samples from both reactors were subjected to protein separation (2-dimensional gel electrophoresis and SDS-polyacrylamide gel electrophoresis) and protein identification (mass spectrometry-MS). Furthermore, bacterial community variations on ammoniated and chloraminated reactors were characterised by sequencing of 16S RNA. The batch rechloramination results obtained from the reactors for the first time established the production of CDP as a microbial response to chloramine stress. The bacterial community characterisations on each of the reactors did not show major differences in identified bacterial strains. However, the EPS producing bacterial strains (AOB, Bradyrhizobium sp. and family Sphingomonadaceae) identified in chloraminated reactors were suspected to be responsible for CDP production. Chloraminated and ammoniated bulk water samples were not resulting in enough concentrations, therefore, for comparison of protein spots and MS analysis, the biofilm samples (which are believed to have more CDP) were analysed. The major proteins detected were ammonia monooxygenase subunit A and putative porin related to Nitrosomonas sp. and Bradyrhizobium sp., respectively. However, their relation to CDP has to be further investigated. Conclusively, every aspect of this study is directing towards discovering a better control mechanism for the microbial/ CDP induced accelerated chloramine decay. Silver is a known inhibitor for several micro-organisms. Therefore, experiments were conducted to reveal the optimum dose of silver on inactivating nitrifying microbes and CDP for controlling the fast decay of chloramine. Interestingly, 2 μg-Ag.L-1 silver (which is far lower than the recommended level- 0.1 mg-Ag.L-1) was found to be effective for improving chloramine residuals in tested bulk waters. This study concludes by further emphasising the need for extensive study/research in further identification of CDP and bacteria communities responsible for chloramine decay in chloraminated drinking water distribution systems

Investigation of the agricultural resources in Sri Lanka

The author has identified the following significant results. Several in-house capabilities were developed. The facilities to prepare color composites of excellent quality were developed, using bulk B/W 70 mm transparencies or 1:1,000,000 positive transparencies. These color composites were studied through optical devices on light tables. A zoom transfer scope was also added, enabling direct transfer of LANDSAT composite data on to base maps

Simultaneous localisation and mapping: A stereo vision based approach

With limited dynamic range and poor noise performance, cameras still pose considerable challenges in the application of range sensors in the context of robotic navigation, especially in the implementation of Simultaneous Localisation and Mapping (SLAM) with sparse features. This paper presents a combination of methods in solving the SLAM problem in a constricted indoor environment using small baseline stereo vision. Main contributions include a feature selection and tracking algorithm, a stereo noise filter, a robust feature validation algorithm and a multiple hypotheses adaptive window positioning method in 'closing the loop'. These methods take a novel approach in that information from the image processing and robotic navigation domains are used in tandem to augment each other. Experimental results including a real-time implementation in an office-like environment are also presented. © 2006 IEEE

Elevating the value of urban location: A consumer preference-based approach to valuing local amenity provision

Estimating the non-market monetary values of urban amenities has become commonplace in urban planning research, particularly following Rosen’s seminal article on hedonic theory in 1974. As a revealed preference method, the hedonic approach decouples the market price of a house into price components that are attributable to housing characteristics. Despite the potential contribution of this theory in a planning context, three main limitations exist in the conventional applications: (1) variable measurement issues, (2) model misspecification, and (3) the problematic common use of global regression. These flaws problematically skew our understanding of the urban structure and spatial distribution of amenities, leading to misinformed policy interventions and poor amenity planning decisions. In this article, we propose a coherent conceptual framework that addresses measurement, specification, and scale challenges to generate consistent economic estimates of local amenities. Finally, we argue that, by paying greater attention to the spatial equity of amenity values, governments can provide greater equality of opportunities in cities

A Comparative Study on Post-Harvest Losses Associated with Upcountry Vegetable before and During COVID -19 Pandemic Situation: A Case of The Welimada Divisional Secretariat Area

Vegetables are essential food items that provide daily nutritional requirements to maintain healthy life for human beings. Therefore, it is necessary to maintain continuous production and supply. The unexpected Covid-19 plague disrupted the production, sale and distribution of vegetables so that producers, traders as well as consumers happened to face unexpected problems. Accordingly, a study was conducted with the main objective to investigate the post harvesting losses associated with upcountry vegetable before and under COVID-19 pandemic situation comparatively. To achieve the main objectives a field survey was carried out by collecting primary data from 16 traders from the Economic Center and 50 farmers from 05 Grama Niladhari Divisions of Welimada divisional secretariat area using stratified sampling technique. Additional information was collected by using interviews with farmers and traders and secondary data. Data was analyzed using quantitative, qualitative methods and paired T tests were performed to confirm the difference between the variables associated with before and during the COVID-19 pandemic statistically. Results reviled that, there was a significant difference (p <0.05) in post-harvest losses coursed at farm, transport and wholesale lelves in marketing of vegetables before and during the COVID-19 pandemic. Several factors affected to increase post-harvest losses and there are the harvesting was delayed, number of barriers were faced during transportation, the economic center has been closed for several days, vegetable prices have fallen and wholesales have declined. It can be concluded that the post-harvest damage to upcountry vegetable has been affected by the covid-19 pandemic. DOI: http://doi.org/10.31357/fhss/vjhss.v07i01.0