Dynamic Release of Solutes from Roof Bitumen Sheets Used for Rainwater Harvesting

Bitumen waterproof sheets are widely used to seal building roofs. Previous works have focused on the mechanical-physical properties of bitumen sheets, as well as their aging and degradation processes, and their impact on sealing properties of the buildings. Due to a growing need over recent years to use rooftops in urban environments for rainwater harvesting purposes, it is highly important to better characterize the quality of the harvested water from the bitumen covered roofs, and to shed more light on the impact of bitumen degradation processes on the release of various components to the harvested roof water. In the present study, the extracted organic and inorganic solutes from bitumen-covered roofs by water flow on the bitumen sheets were examined through a series of experiments, including measurements from the roofs of buildings in the center of Israel during the winter of 2019–2020. The results indicated high levels of organic and inorganic solute loads in the roof water during the first flush of the first rain of the winter, with maximal electric conductivity readings at the order of 4 dS/m. However, it was shown that following the first flush, a ~20 mm of cumulative rainfall was sufficient to wash off all the summers’ accumulated solutes from the roof. After this solute flushing of the roof, harvested rainwater along the winter was of good quality, with electric conductivity readings in the range of 0.04–0.85 dS/m. Moreover, it was shown that bitumen sheets which were exposed to direct sun radiation emitted greater loads of solutes, likely a result of elevated aging and degradation processes. The findings of the present research point to the need to find efficient ways to isolate roof bitumen sheets from direct sun radiation and to design rainwater harvesting systems that will not collect the water drained from the first flush.

A Comparison of Methods to Address Anaerobic Conditions in Rainwater Harvesting Systems

Although historically used in semi-arid and arid regions, rainwater harvesting (RWH) systems have increasingly been used in non-arid and humid regions of the world to conserve potable water and mitigate stormwater runoff. Rainfall characteristics and usage patterns of stored rainwater are distinctly different in (semi-)arid and humid regions, thus presenting a unique set of challenges with respect to their utilization. Coupled with infrequent use, the addition of nitrogen and organic matter via pollen during the spring season can lead to anaerobic conditions within storage tanks, which hinders nitrogen removal, gives stored water an offensive odor, and ultimately discourages use of the water. This study evaluated three measures that can be implemented for new and existing RWH systems to prevent the development of anaerobic conditions within storage tanks: first flush diversion, simulated use, and the continuous circulation of stored water. Study findings indicate that preventing anaerobic conditions via simulated use and recirculation (1) does not necessarily remedy the issue of poor aesthetics within rainwater storage tanks, and (2) can decrease the water quality benefits provided by these systems. Rather, preventing the introduction of pollen and particulate matter to the storage tank via a first flush diverter and minimizing disturbance of settled material in the tank appear to be the most effective methods of addressing the poor aesthetics and odor problems associated with anaerobic conditions.

Qualidade e tratamento de águas pluviais para fins não-potáveis e avaliação ecotoxicológica

Visando a melhorar a disponibilidade hídrica nos grandes centros urbanos, torna-se necessária a busca por tecnologias para conservação, aproveitamento e reúso de água. O uso de fontes alternativas para fins não- potáveis, como o aproveitamento de águas pluviais, apresenta-se como uma alternativa viável para a redução da demanda por água potável, sendo necessário estudar a qualidade da água obtida bem como técnicas de tratamento eficazes para melhoria e preservação da qualidade da água para atendimento de usos mais restritivos. Dessa forma, este trabalho tem por objetivo avaliar a influência da superfície de captação e dos volumes de descarte (first-flush) na qualidade da água precipitada e a eficiência da filtração rápida descendente em areia na melhoria e preservação de sua qualidade. A qualidade das águas bruta e tratada foi avaliada em função dos parâmetros: turbidez, cor aparente, sólidos totais, condutividade elétrica, pH e alcalinidade; bem como ecotoxicidade com o organismo-teste Artemia salina. Os resultados evidenciaram a importância do descarte do início da precipitação na melhoria da qualidade da água reservada e na prolongação da vida útil do tratamento. O tratamento da água por filtração permitiu o ajuste das características físicas e químicas avaliadas em conformidade com a NBR 15.527, além de remover o efeito tóxico, no caso da cobertura de material metálico. Palavras-chave: Água de chuva. First-flush. Filtração. Ecotoxicidade. Artemia salina.

Assessment of Pollutants from Diffuse Pollution through the Correlation between Rainfall and Runoff Characteristics Using EMC and First Flush Analysis

Urban stormwater runoff is an important source of pollution in receiving water bodies, mainly in cities in development. However, strategies to deal with the impacts caused by the runoff discharges, such as implementing a sustainable urban drainage system (SUDS) with optimized management, need information usually obtained through monitoring studies. Brasília is a city that has one of the highest urban growth rates in Brazil, with significant impacts on urban water resources, including diffuse pollution, generated by new unregulated urban developments that initially start being built with precarious sanitation infrastructure. The Vicente Pires (VP) watershed is highly urbanized and comprises two areas that have been intensively occupied more recently, at a fast pace, and do not have yet basic sanitation systems fully implemented. Stormwater quality at the outlet of the VP watershed was analyzed by monitoring the rainfall, runoff flows, and pollutant concentration. Event Mean Concentration (EMC) and first-flush (FF) phenomenon were calculated, and hydrologic characteristics were compared for different events through correlation analysis. During dry periods the flow varied between 0.5 and 1.29 m3/s, while in flood periods the maximum value was 72.17 m3/s, forming floods with great volume. Nitrate during dry periods stands out with its high concentration; the maximum was 1.49 mg/L, while the maximum concentration during the flood events was 0.43 mg/L, probably due to dilution. Ammonia results showed very low values, probably because nitrification is occurring up to the collection point. The EMC values of solids in flood events were higher and can be attributed to river bed scour along the VP watershed. The EMC SS values for the VP watershed are also similar to areas in the initial stages of building development. The EMC values in the dry season indicate strong correlations between some water quality parameters such as NH+3-N and SS, TS and NO−3-N; NO−3-N, and COD. These correlations indicate that these pollutants are probably being generated by the same source, probably sewage discharges. During flood events, the correlation between pollutant loads and peak flow can be associated with the scouring during surface washing off, because greater concentrations of solids and organic matter occur in events with greater flow rates. For the first 30% of the initial runoff volume, about 29% of SS, 38% of NH+3-N, and 35% of reactive P were carried during flood events. It was verified that large values of maximum or mean rainfall intensity are related to the occurrence of First Flush (FF) for most pollutants. Antecedent dry days (ADD) did not influence build-up processes in this watershed; however, they are related to FF occurrence. Data indicate that the sewage and stormwater collection networks were being installed caused a high impact on observed water quality, with high concentrations of solids during flood events. On the other hand, the wastewater collection after the sewer network installation led to a decrease in COD concentrations over time. For sustainable management of diffuse pollution, the adoption of distributed SUDS to enhance runoff volume reduction is a recommended solution for the case.

AVALIAÇÃO DA QUALIDADE DA ÁGUA DE CHUVA DO FENÔMENO FIRST FLUSH E DE VOLUMES ARMAZENADOS EM RESERVATÓRIOS DE SISTEMAS DE ÁGUAS PLUVIAIS NA CIDADE DO RIO DE JANEIRO-RJ

Este trabalho tem como objetivo principal analisar a qualidade da água da chuva a partir da concentração de poluentes depositados em amostras de volumes iniciais precipitados e de volumes armazenados em dois sistemas de águas pluviais, de características distintas, situados na cidade do Rio de Janeiro-RJ, Brasil. A metodologia consistiu em analisar os parâmetros: turbidez, sólidos totais dissolvidos (STD), cloreto e alcalinidade em amostras mensais coletadas nos anos de 2017, 2018 e 2019, e em apresentar as curvas de massa de poluentes em função das vazões afluentes e do cálculo da concentração média desses poluentes dos eventos analisados. As curvas elaboradas para os parâmetros turbidez e cloreto mostram a carga total de poluentes e, também, a variação da qualidade da água de chuva em decorrência da lavagem produzida pelos volumes iniciais precipitados. Os valores médios obtidos em relação à turbidez foram: no CAP1: 34,97 UNT no ponto (FF) e 0,65 UNT no ponto (RR); no CAP2: 20,43 UNT no (FF) e 0,92 UNT no (RR). A partir desses resultados, o trabalho conclui que a intensidade da chuva e o tipo do material de captação das águas pluviais influenciam na remoção de poluentes depositados na superfície do telhado e que a qualidade de amostras coletadas em sistemas de águas pluviais melhora significativamente com a utilização de filtros de retenção de sedimentos e do descarte dos volumes iniciais precipitados.

Reusable rainwater quality at the Ikorodu area of Lagos, Nigeria: impact of first-flush and household treatment techniques

Water scarcity is a huge problem in Africa, and hence rainwater becomes a crucial water source for fulfilling basic human needs. However, less attention has been given by African countries to the effectiveness of common rainwater treatments to ensure the population's health. This study investigates the impact of different household treatment techniques (HHTTs), i.e. treatments by chlorine, boiling, alum, and combination of alum and chlorine, on its storage system using a case study at the Ikorodu area of Lagos state, which is a rural area in Nigeria. The first-flush quality has been particularly studied here, where the microbial reduction through its practice has been examined from five different roofs. One of the investigated roofs was from a residential building, and four were constructed for the purpose of this study. In this study, the physical parameters (i.e. total suspended solids and turbidity) and the microbial parameters (i.e. total coliform and Escherichia coli) of the collected rainwater have been investigated. From the results, it has been observed that: (1) the water quality at the free phase zone is better than that at the tank's bottom; (2) the combination of chlorine and alum gives the best rainwater quality after comparing the application of different HHTTs; and (3) a reduction of about 40% from the original contaminant load occurs in every 1 mm diversion.

Effect of integrated pest management module against major sucking pests of pomegranate (Punica granatum L.)

A field experiment was conducted to assess the performance of IPM module against major sucking pests of pomegranate on seven farmers’ field in the adopted village of Krishi Vigyan Kendra, Khargone (M.P.) during 2018-19 and 2019-20. IPM module comprised Neem oil 1500 ppm @ 3 ml/lit at first flush of leaf+ Need based spray of Imidacloprid 17.8% SL @ 0.25 ml/lit and Thiamethoxam 25% WG @ 0.20 g/liton the rotation of 15 days’. Minimum population of aphids and thrips were recorded in IPM fields and maximum population of the aphids and thrips were recorded in non-IPM fields. Per cent insect control over non-IPM was 50.35% for aphids, and 47.72% for thrips, respectively. Fruit yield for IPM was 156.36 q/ha for both seasons as against 128.43 q/ha in non-IPM. Hence, it may be inferred that IPM module was able to enhance the yield with cost-effective production as against non-IPM.