Urban and semi‐urban planning in developing countries from a water and waste water treatment point of view

Several appropriate technology alternatives are suggested for water and wastewatei treatment in less developed countries. Large‐scale water supply systems employing conventional water treatment methods should be replaced by several small‐scale water treatment units utilizing appropriate water treatment methods.

Conventional sewerage systems should be replaced by low cost on‐site sanitation systems and several other low‐cost wastewater treatment methods such as oxidation ponds, aerated lagoons and anaerobic lagoons. Wastewater renovation and re‐use should be actively encouraged in view of dwindling water resources in these countries.     

Rethinking water reform policies as a ‘wicked problem’ the case of urban water supply in Ghana

Based on the theory of ‘wicked problem’ this paper investigates the causes of unsuccessful reform of urban water utilities in Accra, Ghana. The authors of this paper argue that reforms based only on managerial perspectives are not enough. Taking into account institutional and social issues is a key for the success of such reforms. Donors and international agencies lack such outlook and therefore fail to develop effective water policy reforms in developing countries generally. The paper discusses inter-twined and multi-dimensional institutional constraints that hinder the development of an appropriate approach to water utility reform in Accra.     

Urban water security - what does it mean?

ABSTRACT

This research is focussed on understanding what urban water security means – a surprisingly elusive concept given the global shift from rural to urban living. We first make the case for a distinct urban water security definition. We then identify 25 unique water security definitions, of which three relate to the urban context but all with scope for improvement. Applying novel indices, we assess the prevalence, complexity and evolution of themes and dimensions within all definitions and find a stable spectrum of themes; but note a shifting emphasis towards environmental and social dimensions, away from quality and quantity of supply. Overall the definitions are becoming more comprehensive by simply listing more outcomes to be achieved. Instead of this ‘shopping-list’ approach, we propose a simplified urban water security definition with a focus on agreement of needs with community stakeholders, while using the themes to guide what the objectives might be.     

Hydration of high-calcium quicklime with methanol–water mixtures

In this study, hydration of quicklime was accomplished with different methanol–water mixtures. The greater the percentage of methanol, the more intense was the suppression of the hydration conditions. The reactivity was not greatly affected by the presence of methanol up to 20%, while for hydration mixtures with 30 to 60% methanol a great reduction of reactivity was observed. In all cases of hydration the complete conversion of CaO into Ca(OH)₂ was established by the XRD method. From the SEM study it was ascertained that in a percentage of up to 20% methanol, a normal hydration was observed, expressed by aggregates of hydrated lime grains, whereas the hydration in mixtures of 30–60% methanol, progressively leads to the formation of tabular crystals, the size of which increases with the methanol percentage. What is more important is that the maximum hydration temperature decreases up to 12.5 °C for hydration mixtures up to 20% methanol without the quality of the produced hydrated lime being affected.     

What affects public acceptance of recycled and desalinated water?

This paper identifies factors that are associated with higher levels of public acceptance for recycled and desalinated water. For the first time, a wide range of hypothesized factors, both of socio-demographic and psychographic nature, are included simultaneously. The key results, based on a survey study of about 3000 respondents are that: (1) drivers of the stated likelihood of using desalinated water differ somewhat from drivers of the stated likelihood of using recycled water; (2) positive perceptions of, and knowledge about, the respective water source are key drivers for the stated likelihood of usage; and (3) awareness of water scarcity, as well as prior experience with using water from alternative sources, increases the stated likelihood of use. Practical recommendations for public policy makers, such as key messages to be communicated to the public, are derived.     

Influence of initial dry density and water content on the soil–water characteristic curve and suction stress of a reconstituted loess soil

In the northwest of China, many loess landslides have occurred without clear triggering factors (i.e., rainfall, earthquake, human activities, etc.). To better understand and analyze the hydro-mechanical properties of these slopes and then provide evidence for their stability analysis subjected to matric suction, it is essential to clarify the soil–water characteristic curve (SWCC). In this study, we conducted a set of experimental trials to examine the influences of initial dry density, water content upon the SWCCs of a loess soil taken from a loess landslide area, by using a conventional volumetric pressure plate extractor. Two common SWCC models have been investigated to evaluate which one is better for loess soil. The suction stress characteristic curves (SSCCs) were also estimated and analyzed. We found that behaviors of SWCCs would be different when the matric suction was greater than a certain value. The two SWCC equations have approximately the same performance in describing the SWCC. The rates of desorption decrease and residual water content increases with increasing the initial dry density, while the initial dry density has little, if any, influence on the air-entry value (AEV). The specimen compacted under higher initial water content would exhibit a higher AEV value and residual water content but lower rate of desorption as compared with the lower initial water content. The magnitude of suction stress had an approximately linear relationship with matric suction before the AEV value, the SSCC shapes will be markedly varied with the initial dry density and water content.     

Urban hydrology and water management – present and future challenges

Urban hydrology is an applied science that will have an increasing role to play in the sustainability of human societies. Facing present growth of urban population, it is increasingly difficult to find and utilize new sources of water necessary to satisfy growing water demand. For the poor, the residents of peri-urban and squatter areas, an ultimate poverty, the poverty of lacking clean water, is a result. To remove this kind of poverty should be a first priority target for all people and, especially, for people dealing with water management in urban areas. Growth of urban areas brings significant changes in physical properties of land surface increasing integrated vulnerability of inhabitants, agricultural land and rural ecological life supporting systems. Performance of technical solutions depends on climate as well as on social, economical and cultural conditions. Findings from urban hydrological studies based on collection of urban hydrological data, calculations and modeling constitute a necessary fundamental for meaningful water management not only in urban areas but also in entire river basins. Future challenges in urban water management include development of new technical solutions as well as logistic and organizational methods in order to turn present problems into future opportunities. The following current and emerging challenges are discussed in the paper: delivery of drinking water supply for growing cities, water for sanitation versus sanitation without water, recycling of wastewater nutrients, wastewater irrigation, urban agriculture, water to feed depleted aquifers, thoughts about possible future new system solutions, social equity and transfer of knowledge and new technology.     

Sorption removal of Fe(CN)6 3− ion impurities from water and evaluation of water quality by the biotesting method

The sorption removal of Fe(CN)₆ ^3? ion impurities from water was investigated. A specially synthesized magnesium-aluminum double hydroxide with the hydrotalcite-type structure was used as a sorbent. The biotesting method used for various test objects proved the efficiency of sorption removal of Fe(CN)₆ ^3? from water.     

Habitat quality–physicochemical water quality–littoral macroinvertebrate community nexus in Lugo Lake (Ethiopia): Priorities for sustainable water resources management

The integration of water quality characteristics with habplot-based habitat quality assessment score (HabQA) has received little attention in ecological quality assessment studies. This study investigated the macroinvertebrate community structure in relation with lake habitat quality and physicochemical water quality variables in Lugo Lake (Ethiopia). Twelve sampling sites (eight agricultural and four recreational) were included. The variation among macroinvertebrates data was significantly explained by HabQA score and soluble reactive phosphorus. The study revealed the greater importance of habitat quality characteristics in comparison with the other conventional physicochemical characteristics on macroinvertebrate community structure. We strongly recommend the use of HabQA system while studying macroinvertebrate community structure for a deeper understanding of the environmental functioning of tropical lakes. The results suggested the need to apply integrated and sustainable protection and management of the lake catchment (including wetlands) to enhance the ecological integrity and hence biodiversity of lakes.     

The role of partnerships in water‐related research in Palestine

This study analyses the good effect of science and engineering inputs from partnerships and applied research in promoting sustainable management of water and environmental resources in Palestine. The capacity building achieved during the past 10 years at the Institute of Environmental and Water Studies (IEWS) is reviewed. Palestine faces major constraints, and these affect everyone and everything. A problem‐solving approach can be beneficial.     

Chemistry of tap water in Sri Lanka‐implications on health

A preliminary survey on the chemical quality of tap water in Sri Lanka has been carried out and has been grouped into three categories depending on the source of the water. It was revealed that in certain parts of Sri Lanka, the tap water does contain excess quantities of lead. The Piper trilinear diagram shows that much of the tap water of Sri Lanka belongs to the Ca#shMg‐HCO₃ type. Low pH values have also been observed in certain areas and could bring out excess dissolved ions into the tap water. In view of the fact, that only a small percentage of the population of Sri Lanka have access to piped water, no serious health hazards due to the poor quality of the tap water have been encountered.     

Aquifer characteristics and water quality of Miocene–Pleistocene sediments, Kuwait

Al-Atraf is one of the water well fields of Kuwait supplying Kuwait City with the brackish groundwater obtained from the Kuwait Group aquifer of Miocene–Pleistocene age. The study determined the hydrogeological and hydrochemical characteristics of the groundwater in order to identify the major chemical processes that influence the groundwater quality of the study area. The results of the aquifer test analyses indicate that the Kuwait Group is a confined to semi-confined aquifer, with a transmissivity ranging between 62 and 321 m²/day. The flow net analysis implied that the groundwater moves from southwest to northeast. The estimated transmissivity values agree well with those calculated from the aquifer test. The results of the chemical analyses data of the Al-Atraf field show that the groundwater is mainly brackish, of NaCl and Na₂SO₄ water types. The groundwater is undersaturated with respect to halite, gypsum and anhydrite and supersaturated with respect to quartz, dolomite and calcite in the direction of groundwater flow. The average Pco₂ of the groundwater is higher than the Pco₂ of the earths atmosphere indicating that the groundwater is supplied with CO₂ during the infiltration processes and dissolves the carbonate minerals under closed-system conditions.     

Impact of household plumbing fixtures on drinking water quality — a review

This paper reviews the pertinent literature published since 1970 on the impact of household plumbing systems on drinking water quality through the leaching of metals such as cadmium, copper, iron, lead, tin and zinc into potable water. Copper is found to be more easily and extensively leached than lead. Copper is leached almost exclusively from copper tubing. Lead can be leached from lead pipes, lead‐tin solders and faucets in residences. Zinc and tin require to be monitored as well.     

Does public ownership of utilities matter for local government water policies?

What differentiates local governments that implement water policies on equity and the environment? Analyzing a 2015 national survey of 1,897 U.S. municipalities, we find municipalities that own their water utilities are more likely to report policies to protect low-income residents from disconnection and implement water resource management. Respondents from 8% of municipalities report protecting residents from disconnection. State economic regulation of municipally owned utilities and Democrat-majority municipal governments are positively associated with local policies to protect low-income households from shutoffs but bear no association with resource management. Both municipal ownership of utilities and state economic regulation may play a role in meeting certain local water policy goals.     

Palygorskite–TiO2 nanocatalysts for photocatalytic degradation of tebuconazole in water

Palygorskite–TiO₂ nanoparticles are frequently used as nanocatalysts. In the present study, two different nanocatalysts were developed based on the use of different palygorskite–TiO₂ ratios: 40–60 and 10–90. The nanocomposites were investigated for the photocatalytic degradation of the common fungicide tebuconazole (TEB), under aquatic conditions. The samples were extensively characterized by X-ray powder diffraction, attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy and N₂ specific surface area (SSA) by Brunauer–Emmett–Teller (BET) analytical techniques. The TiO₂ nanoparticles were successfully dispersed on the mineral's surfaces and the photocatalytic activity reached 88.4% for the palygorskite–TiO₂ ratio of 40:60, where the dispersion was better as proved by the total pore volume and BET parameters (0.49 cm³/g and 258 m²/g compared to 0.33 cm³/g and 220 m²/g of the 10:90 ratio). The photocatalytic efficiency of the proposed materials was significantly higher than Degussa P25 (33.2%), and that makes the palygorskite–TiO₂ nanocomposites very promising for advanced application in fungicides' degradation in aquatic environments.     

Indirect evaporative cooling potential in air–water systems in temperate climates

Recent developments have prompted a review of evaporative cooling technology as an effective means of cooling modern deep plan buildings. Prominent among these developments is the success of high temperature sensible cooling systems, particularly, chilled ceilings, which require a supply of cooling water at 14–18 °C. Crucial to the success of evaporative cooling technology, as a significant means of cooling in modern applications, is the ability to generate cooling water, in an indirect circuit, at a temperature which closely approaches the ambient adiabatic saturation temperature (AST) or wet bulb temperature (WBT). Recent experimental research has demonstrated that it is technically viable to generate such cooling water at a temperature of 3 K above the ambient AST.While the frequency of ambient AST occurrence can be obtained from meteorological sources, there is little in-depth analysis of the potential for this form of cooling water generation, based on the approach temperatures which have now been shown to be viable. The decision to use an evaporative cooling system depends largely on an assessment, in-depth, of net energy saved against capital expended. Such an assessment requires detailed data on the availability of cooling water, generated by evaporation, for each location. This paper quantifies evaporative cooling availability in-depth for a northern and southern European city, Dublin and Milan and suggests a method of analysing such data for any world wide location, for which suitable meteorological records are available. The paper, incorporates recent experimental research findings and bases the availability analysis on meteorological test reference weather year data.The results of this research confirm a major potential for the generation of cooling water by evaporative means, which can be used to provide effective cooling of deep plan buildings by means of contemporary water based sensible cooling systems, such as fan coil systems, radiant chilled ceiling panels and ceiling cooling convectors (chilled beams). While the technique offers most potential in locations with a northern European temperate climate, it has significant potential to contribute to cooling in some southern European cities, during the non-summer months and also at other times, particularly where load shaving techniques are incorporated.     

Does the reuse of PET bottles during solar water disinfection pose a health risk due to the migration of plasticisers and other chemicals into the water?

Solar water disinfection (SODIS) is a simple, effective and inexpensive water treatment procedure suitable for application in developing countries. Microbially contaminated water is filled into transparent polyethylene terephthalate (PET) plastic bottles and exposed to full sunlight for at least 6 h. Solar radiation and elevated temperature destroy pathogenic germs efficiently. Recently, concerns have been raised insinuating a health risk by chemicals released from the bottle material polyethylene terephthalate (PET). Whereas the safety of PET for food packaging has been assessed in detail, similar investigations for PET bottles used under conditions of the SODIS treatment were lacking until now. In the present study, the transfer of organic substances from PET to water was investigated under SODIS conditions using used colourless transparent beverage bottles of different origin. The bottles were exposed to sunlight for 17 h at a geographical latitude of 47° N. In a general screening of SODIS treated water, only food flavour constituents of previous bottle contents could be identified above a detection limit of 1 μg/L. Quantitative determination of plasticisers di(2-ethylhexyl)adipate (DEHA) and di(2-ethylhexyl)phthalate (DEHP) revealed maximum concentrations of 0.046 and 0.71 μg/L, respectively, being in the same range as levels of these plasticisers reported in studies on commercial bottled water. Generally, only minor differences in plasticiser concentrations could be observed in different experimental setups. The most decisive factor was the country of origin of bottles, while the impact of storage conditions (sunlight exposure and temperature) was less distinct. Toxicological risk assessment of maximum concentrations revealed a minimum safety factor of 8.5 and a negligible carcinogenic risk of 2.8 × 10⁻⁷ for the more critical DEHP. This data demonstrate that the SODIS procedure is safe with respect to human exposure to DEHA and DEHP.     

Assessing integrated water management options for urban developments – Canberra case study

Urban water services in the Australian Capital Territory (ACT) are currently provided through conventional centralised systems, involving large-scale water distribution, wastewater collection, water and wastewater treatment. A study was conducted to assist Environment ACT in setting broad policies for future water services in Canberra. The current paper presents the outcomes of a study examining the effects of various water servicing options on water resources and the environment, for two townships in Canberra, one existing and one greenfield site. Three modelling tools were used to predict the effects of various alternative water servicing scenarios, including demand management options, rainwater tanks, greywater use, on-site detention tanks, gross pollutant traps, swales and ponds. The results show that potable water reductions are best achieved by demand management tools or a combination of greywater and rainwater use for existing suburbs, while third pipe systems are preferred for greenfield sites. For this specific climatic region and end use demands, modelling predicted increased water savings from raintanks compared to greywater systems alone, with raintanks providing the additional benefit of reduced peak stormwater flows at the allotment scale. Rainwater and stormwater reuse from stormwater ponds within the catchments was found to provide the highest reduction in nutrient discharge from the case study areas. Environment ACT amended planning controls to facilitate installation of raintanks and greywater systems, and commenced a Government funded rebate scheme for raintanks as a result of this study.