A.R. Mels

Resource management as a key factor for sustainable urban planning

Due to fast urbanization and increasing living standards, the environmental sustainability of our global society becomes more and more questionable. In this historical review we investigate the role of resources management (RM) and urban planning (UP) and propose ways for integration in sustainable development (SD). RM follows the principle of circular causation, and we reflect on to what extent RM has been an element for urban planning. Since the existence of the first settlements, a close relationship between RM, urbanization and technological development has been present. RM followed the demand for urban resources like water, energy, and food. In history, RM has been fostered by innovation and technology developments and has driven population growth and urbanization. Recent massive resource demand, especially in relation to energy and material flows, has altered natural ecosystems and has resulted in environmental degradation. UP has developed separately in response to different questions. UP followed the demand for improved living conditions, often associated to safety, good manufacturing and trading conditions and appropriate sanitation and waste management. In history UP has been a developing research area, especially since the industrial era and the related strong urbanization at the end of the 18th century. UP responded to new emerging problems in urban areas and became increasingly complex. Nowadays, UP has to address many objectives that are often conflicting, including, the urban sustainability. Our current urban un-sustainability is rooted in massive resource consumption and waste production beyond natural limits, and the absence of flows from waste to resources. Therefore, sustainable urban development requires integration of RM into UP. We propose new ways to this integration.

The Urban Harvest Approach as an Aid for Sustainable Urban Resource Planning

Now that more than half of the worlds population lives in cities, improving urban resource cycles is crucial for sustainable urban development. Currently cities are highly dependent on external supplies of water, energy, nutrients, and other materials, while local possibilities of self‐production of such resources are generally overlooked. This article describes a novel method, the urban harvest approach (UHA), its rationale, and the steps toward sustainable urban resource planning. The UHA is based on the urban metabolism concept. Herein, a city is regarded to have multiple potentials in the form of untapped primary and secondary (already used) resources that can be utilized. The UHA works on the principle that urban systems and their direct peri‐urban surroundings can become self‐sufficient by applying three strategies: minimizing demand, minimizing outputs, and multisourcing. An elaboration of the UHA for the resource “water” at the building scale is also presented in this article. A freestanding house in the Netherlands and a similar house in Australia were studied, with a focus on indoor consumption. Results showed a 40% demand reduction when water‐saving technologies were implemented. In both cases, after demand minimization, local resources were sufficient to cover the demand by recycling grey water and harvesting rainwater. These findings confirm that a multimeasure implementation according to the three different strategies is needed to achieve sustainable urban water systems. The UHA helps to structure large influences of urban context on water and other resource cycles as an aid to urban planners and water managers in designing sustainable urban areas.

Evaluating the potential of improving residential water balance at building scale.

Earlier results indicated that, for an average household, self-sufficiency in water supply can be achieved by following the Urban harvest Approach (UHA), in a combination of demand minimization, cascading and multi-sourcing. To achieve these results, it was assumed that all available local resources can be harvested. In reality, however, temporal, spatial and location-bound factors pose limitations to this harvest and, thus, to self-sufficiency. This article investigates potential spatial and temporal limitations to harvest local water resources at building level for the Netherlands, with a focus on indoor demand. Two building types were studied, a free standing house (one four-people household) and a mid-rise apartment flat (28 two-person households). To be able to model yearly water balances, daily patterns considering household occupancy and presence of water using appliances were defined per building type. Three strategies were defined. The strategies include demand minimization, light grey water (LGW) recycling, and rainwater harvesting (multi-sourcing). Recycling and multi-sourcing cater for toilet flushing and laundry machine. Results showed that water saving devices may reduce 30% of the conventional demand. Recycling of LGW can supply 100% of second quality water (DQ2) which represents 36% of the conventional demand or up to 20% of the minimized demand. Rainwater harvesting may supply approximately 80% of the minimized demand in case of the apartment flat and 60% in case of the free standing house. To harvest these potentials, different system specifications, related to the household type, are required. Two constraints to recycle and multi-source were identified, namely i) limitations in the grey water production and available rainfall; and ii) the potential to harvest water as determined by the temporal pattern in water availability, water use, and storage and treatment capacities.

The MobiSan approach: informal settlements of Cape Town, South Africa

Pook se Bos informal settlement and the Cape Town Water & Sanitation Services Department are partnering on an urban sanitation project with a Dutch Consortium consisting of Lettinga Associates Foundation (LeAF), Landustrie Sneek and Vitens-Evides International. The aim of the project is to improve the basic sanitation services provided in informal settlements through the implementation of the MobiSan approach. The approach consists of a communal Urine-Diversion and Dehydration Toilet (UDDT) built in a former sea shipping container. The system is independent of water, electricity or sewerage connection and it is maintained by full-time community caretakers who also act as hygiene promoters. The project seeks to link sanitation services with hygiene promotion in informal settlements while enhancing user satisfaction and reducing costs in providing basic sanitation services. This paper describes the preliminary experiences and lessons learnt during the implementation and evaluation of the MobiSan prototype and discusses its potential for replication. The MobiSan has proved to be an appropriate option by means of dealing successfully with shallow groundwater table, land availability and high settlement densities. In addition it has been demonstrated to be cost-competitive in terms of operating cost compared to chemical toilets.

Cationic organic polymers for flocculation of municipal wastewater - Experiments and scenario study

Organic polymers can be favourable flocculants in comparison with inorganic (metal-)flocculants because chemical sludge production is absent and the increase in salt concentration of the effluent is low. Jar test experiments showed that a higher weight (8.106 g/mol; (+) 24%) cationic polyacrylamide gave good flocculation results, with turbidity- and CODparticulate removal efficiencies of 65-90% and a TSS removal of > 90% at relatively low dosing concentrations. Rapid coagulation mixing conditions were optimal with a mixing time of 30 s (G = 800 s-1). A decrease in low flocculation mixing time from 180 s to 30 s (G = 50 s-1) resulted in a decrease in particle removal of 25%. A scenario study was conducted to estimate the costs involved and to quantify the environmental impacts. The scenario study showed that the total costs of a complete wastewater treatment system based on coagulation-flocculation with organic polymers are in the same range (-5%) as those of a system with FeClv Total sludge production is 15% lower. Salinisation is of the order of +0.2 mg Cl per litre effluent for dosing polymer and +29 mg Cl per litre effluent for dosing FeCl3.

Retention and distribution of Cu, Pb, Cr, and Zn in a full-scale hybrid constructed wetland receiving municipal sewage

This study was conducted to investigate the retention and distribution of Cu, Pb, Cr, and Zn in a hybrid constructed wetland (CW) that consists of both vertical baffled flow wetlands (VBFWs) and horizontal subsurface flow wetlands (HSSFs) with unique flow regimes and oxygen distribution. The heavy metal concentrations in water, sediments, and plant tissues in the hybrid CW were analysed. The removal of heavy metals from the water stream in the monitoring period was not statistically significant. Metal concentrations in the sediments generally decreased along the wastewater treatment process. The reductive anaerobic condition in the VBFW may promote the sulphate reduction and form highly insoluble Cu, Pb, and Zn sulphides, resulting in the higher concentration of the bivalent cations in the VBFW sediments than the corresponding values in the HSSF; however, the aerobic and anoxic environments in the HSSF enhanced the removal of Cr with the co-precipitation of iron and manganese oxides, and their hydroxides. Metal concentrations in plant tissues were not significantly influenced by the concentrations in sediments, while roots contained statistically higher metal concentrations than stems and leaves. The sediments stored 94.01, 86.31, 95.85, and 89.51% of the total Cu, Pb, Cr, and Zn retained in the hybrid CW system, respectively, while only small fractions (<10%) were accumulated in the harvestable macrophyte tissues. It is important to clean not only the accessible sediments in free water surface tank and ponds but also the embedded sediments in vegetated beds for the sustainable removal of heavy metals.