Aware of this situation, in 2005, the Autonomous Community of Madrid Government presented one of its largest and most ambitious plans for the region’s environmental consolidation. The plan was called “Plan Madrid Dpura” (Madrid Wastewater Treatment Plan) and the tasks of drafting, executing and operating the plan were entrusted to Canal de Isabel II as was, even more crucially, its complete financing. Investment in the Madrid Dpura plan amounted to €700 million, of which more than€200 million were allocated exclusively to the regional strategy for water reclamation and reuse.
The “Water Reuse Plan” for urban uses was expounded by the Autonomous Community of Madrid, with an initial development stage that would last until 2014. Actions to date have been designed to improve and extend wastewater collection and treatment facilities to cover all the municipalities in the Madrid region. The plan includes the construction of 20 tertiary treatment plants to supplement the 10 existing ones, in order to make these resources available and incorporate them into the new distribution system as reclaimed water (Figure 8.1). These facilities are currently being developed.
The success of this plan would depend on two main pillars: the sizeable investment that was required in order to implement it and the commitment of customers to use recycled water. With this in mind, in 2005, Canal de Isabel II developed master plans covering a total of 51 municipalities of the Autonomous Community with a view to signing agreements with the town councils of the municipalities involved for the execution of the projects that would be drafted.
The plan developed by the public company Canal de Isabel II is the largest in Europe at this time and constitutes one of its most significant investments which, when combined with other measures that have been adopted (wells, water transfers and
Figure 8.1 Schematics of the water reuse network in Madrid.
MilestonesinWaterReuse:TheBestSuccessStories
other alternatives), will make it possible to guarantee the future water supply to the population of the Autonomous Community of Madrid, particularly in times of drought.
These actions are supplemented by a reclaimed water ring over 140 km long which transports the reclaimed water produced in the tertiary treatments of Madrid’s main wastewater plants for the irrigation of 295 ha of the city’s green areas.
Project objectives, incentives and water reuse applications
With the implementation of this Plan, it is expected that 70 million m3(Mm3) of reclaimed water will be produced each year, of which around 40% will be used in the city of Madrid alone. The remaining 60% will be used to supply 51 municipalities of the Autonomous Community of Madrid, benefiting 2.5 million of the region’s inhabitants. The reclaimed water supply will irrigate 6500 ha of public green areas, the equivalent of 9300 football fields, year round, regardless of water reserve levels. It may also be allocated to industrial uses, street flushing and the irrigation of golf courses. All this will permit 9 million m3of drinking water to be saved per year. In order to distribute such a significant volume of reclaimed water, the Madrid Dpura Plan also foresees the construction of a water distribution network consisting of 1200 km of pipelines that will convey recycled water to users requiring this service.
8.2 TECHNICAL CHALLENGES OF WATER QUALITY CONTROL
Water quality standards
Water reuse in Spain must meet the regulations of the Royal Decree 1620/2007 issued on 7 December 2007, which establishes the legal requirements for water reuse. The targeted water quality parameters required for the major uses of recycled water in Madrid are given in Table 8.1.
According to the intended uses and the related quality requirements, Canal de Isabel II has selected the most appropriate tertiary treatments described in the following sections.
Treatment trains for water recycling
The tertiary treatment processes currently in operation in Madrid follow the conventional scheme including physical-chemical treatment and settling or air flotation units, filtration and disinfection. In some specific cases, more advanced technologies such as ultrafiltration and reverse osmosis have been adopted to obtain higher quality recycled water that can be used in urban areas such as for the irrigation of parks, green areas, golf courses or for industrial processes.
Table 8.1 Water quality requirements for water reuse in Spain according to the Royal Decree 1620/2007.
Use of purified wastewater
a) Processing and cleaning waters except in the food industry
– 10,000 cfu/100 mL 35 mg/L 15 NTU b) Other industrial uses
c) Processing and cleaning waters for use in the food industry
1 egg/10 L 1000 cfu/100 mL 35 mg/L – d) Refrigeration towers and evaporative condensers 1 egg/10 L Absent 5 mg/L 1 NTU Recreational uses
For thephysical-chemical treatment, typical processes include static mixers (although some of them also have mixing and flocculation chambers), followed by lamellar settling tanks (Figure 8.2a) or air flotation units, which enable the removal or reduction of parasitic eggs or cysts, detergents, remaining suspended solids and associated organic matter. The chemicals used in this process are usually inorganic coagulants (iron or aluminium salts) and organic polymer-based flocculants (polyelectrolytes), which are sometimes combined.
Filtrationis the next step after physical-chemical treatment (Figure 8.2a and b), and its purpose is to retain any remaining suspended particles by means of porous media. A variety of filtration systems are implemented such as pressurised sand filters (the most commonly used so far, over 40% of facilities), moving bed continuous washing sand filters (21%), ring filters (13%), open sand filters (13%), cloth filters (4%), micro-sieves (almost 5 %).
The purpose ofdisinfection is to remove pathogenic microorganisms through the addition of chemicals (hypochlorite, chlorine gas, ozone) or physical devices (UV light). The target pathogenic microorganisms include those of viral origin (poliomyelitis, hepatitis, gastroenteritis), bacterial origin (cholera, typhus, dysentery, tuberculosis) and parasite origin. All the tertiary treatment facilities in Madrid are equipped with UV lamps installed in closed reactors (Figure 8.3a), except for one facility, where the UV system is installed in channels.
Theadvanced treatmenttechnologies in operation include various processes that are classified according to pore size and thedriving force responsible for permeate flux (Figure 8.3b): Microfiltration (MF), Ultrafiltration (UF), Reverse Osmosis (RO).
An ultrafiltrationsystem was implemented in one of the facilities dedicated to golf course irrigation. A new advanced recycling plant is under construction using ultrafiltration followed by reverse osmosis and disinfection to supply process water to a paper mill, which manufactures recycled paper.
In summary, the conventional tertiary treatment included in the“Water Reuse Plan”of Madrid aims to produce reclaimed water for irrigation of green areas and golf courses, while the advanced treatments are dedicated to producing water for industry.
Figure 8.2 Views of tertiary pre-treatment processes: from left to right lamella settling (a), ring filters (b) and sand filters (c).
Figure 8.3 Views of UV disinfection (a) and ultrafiltration modules (b).
MilestonesinWaterReuse:TheBestSuccessStories
Water quality control and monitoring
The quality control of reclaimed water is also regulated in Royal Decree 1620/2007 as illustrated by Table 8.2.
Frequency range goes from twice-weekly up to monthly depending on water uses (urban, agricultural, industrial and recreational).
According to Spanish regulations, the reclaimed water quality control programme determines the sampling location, as well as the minimum frequency, analytical methods to be used and limit concentration values for each parameter. Finally, it also defines the guidelines for assessing the reclaimed water quality and the contingency plan in the case of non-compliance.
Sampling is performed at various points throughout the reclaimed water production and distribution system. Essential points are therefore the tertiary treatment effluent, holding tank outlets, automatic sampling stations distributed throughout the network and the points of water use.
In addition to the controls required by the regulations, Canal de Isabel II has a series of Official Sampling Stations (O.S.S.) located throughout the reclaimed water network to provide data regarding water quality so that the appropriate measures can be taken in the event of deviation from the established standard. The parameters measured automatically are total chlorine and turbidity.
In the event of non-compliance, service is suspended until the cause is identified and resolved. During the suspension period, water from the urban drinking water network can be used as an alternative supply to ensure the continuity of service. For this reason, all reclaimed water tanks in the distribution system have an alternative drinking water supply.
In order to avoid cross contamination between the reclaimed water and drinking water supplied to a customer, it is absolutely essential that a cross-connection control is performed before the start-up and periodically during operation of the dual distribution system.
8.3 WATER REUSE APPLICATIONS
The main uses of reclaimed water in the Autonomous Community of Madrid are irrigation of public parks and gardens (Figure 8.4), golf courses, street flushing and industrial uses.
Table 8.2 Monitoring frequency of recycled water according to the Royal Decree 1620/2007.
Parameter Minimum frequency range
Intestinal Nematodes Weekly-fortnightly
Escherichia coli 2 times/week-weekly
Suspended solids Daily-weekly
Turbidity Daily-weekly
Other contaminants1 Weekly-monthly
1Legionella.: 3 times/week, only for industrial use.
Figure 8.4 Views of landscape irrigation in Madrid.
TheexcitingchallengeofwaterreuseinMadrid111
In public parks it is essential that the existing irrigation networks (previously fed with drinking water) be disconnected from the drinking water network for fountains, before recycled water is fed into them. The development of the Water Reuse Plan has meant that since mid-2011 almost 60 public parks, covering an area of more than 275 ha, can be irrigated using reclaimed water.
Similarly, a number of points throughout the urban areas have been furnished with hydrants in order to allow filling of reclaimed water tankers used to flush town streets.
Particularly notable is the case of the supply of reclaimed water into the manufacturing process in a paper mill, whose production amounts 470,000 tonnes a year of 100% recycled paper, with an annual water consumption of 4.3 Mm3. The significant volume of drinking water consumed by this paper mill, combined with the increasingly frequent periods of drought threatening the Autonomous Community of Madrid, made it apparent that alternative water sources were needed in order to ensure optimum operation of the plant and guarantee its supply at all times and under any circumstances. In this context, an agreement was signed between Canal de Isabel II and the paper mill to fully replace the drinking water supply with recycled water. The use of reclaimed water in the factory’s industrial processes requires water with a low salt content and no risk of contamination from bacteria, protozoa or viruses and of particular importance, no trace of endotoxins. This last aspect is critical in this particular case due to the generation of aerosols in some of the manufacturing processes.
Based on these requirements, the recycling facility for the paper mill was designed with a flow capacity of 12,400 m3/day, with a physical-chemical treatment, sand and activated carbon filtration, ultrafiltration using hollow fibre membranes, two-stage reverse osmosis and final remineralisation of the treated water. The total investment for this advanced tertiary treatment is€19 million.