THE AQUASAVE PROJECT

THE AQUASAVE PROJECT:

WATER SAVING SYSTEM IN HOUSEHOLDS

ENEA (Italian National Agency for New Technologies, Energy and Environment); ARPA (Environment Regional Agency of Emilia Romagna); Az.USL (Bologna City Health District); G. DOZZA Cooperative society; Scagliarini (Architect); SeaBo S.p.A. (Energy and Environment Company of Bologna); Bologna Municipality.

ABSTRACT

Water is precious for life and its needs. Water must be protected and used in an appropriate way. Drinkable water use in household is not always appropriate; only a small percentage is used for drinking or food preparation (~ 4%) the remaining part is consumed for other uses.

The aquasave project aims to study and evaluate the potentiality of drinkable water saving in households (see figure 1), by means of an experimental new model of water resources management implemented in the city of Bologna in Italy.

Results show a valid possibility for drinking water saving in households.

KEY WORDS

Potable water saving, greywater reuse, rainwater use, components at low water consumption.

INTRODUCTION

Water demand in the world is always high. Water resources are not unlimited. In geographic areas where the resources are not able to satisfy demand, water saving on traditional consumption could be a way to contribute to the solution of the problem.

In this framework the Aquasave Project (AP) is dealing with the consumption saving of potable water in the city, by means of a new experimental way of resource consumption management.

The European Commission, in the framework of the life-environment action (Life 97 Environment /IT/000106), financed 50% of total costs.

METHOD

The water management system had been installed in a residential building of eight flats; the construction phase had been completed by the autumn of 2000 (see photo 1). The system maximizes reuse by a) greywater reuse system (see figure 2): it collects, treats and sends greywater (coming from showers, bathtubs, and washbasins located in bathrooms) to toilet flushing; b) rainwater use system (see figure 3): it collects, treats and sends rainwater to dishwashers and washing machines. The system minimizes waste production by installation in the flats of components at low water consumption.

Figure 1. Water management.

Photo1. Construction phase.

MATERIALS

Building

The building has eight flats distributed on three storeys. The floor of the plant room, where the treatment plant is installed, is located three meters under the ground-floor. The roof surface is about 200 m². The plant room surface is about 90 m². The plant room is about 2.9 m high. The persons living in the flats are 22.

Greywater Reuse System

Greywater coming from bathroom washbasins, bathtubs, and showers (see figure 2) is collected through an appropriate network, pre-filtered (a grid stops solids: about 500 µm) and sent to the collection tank in the plant room; then greywater is filtered (through quartzite filter: about 50 µm), disinfected, and sent to the storage tank. Afterwards, through a dedicated distribution network, a loading system sends the treated greywater to the flats and then to the toilet flushing cisterns. The treatment plant works automatically.

Figure 2. Reuse of treated greywater.

Rainwater Use System

Rainfall coming from the roof (see figure 3), collected through a dedicated network, flows to the plant room. Here: first rainwater, which could be highly polluted and rich in particulate, is separated and sent to the sewer (depending on mm of rainfall); a pre-filter stops (through grid: about 500 µm) leaves, pieces of paper, birds’ feathers and faeces, and other solids; so pre-treated rainwater flows into the collecting tank. Afterwards, rainwater is filtered (through quartzite filter: about 50 µm, see photo 2), disinfected and sent to the storage tank to have a reserve of water to be used in periods of little rainfall. Afterwards, through a dedicated distribution network, a loading system sends the treated rainwater to the flats and then to dishwashers and washing machines. The appliances use rainwater at washing cycle beginning (~66% of total washing machine consumption), and potable water at cycle end for final rinse. The treatment plant is automatic.

The very low calcium and salt concentration (a) allows reduction of detergent consumption, (b) reduces need of salt regeneration in dishwasher ion-exchangers.

Rainfall is about 670 mm year^-1. The surface of the roof is ~200 m². Rainwater availability for appliance consumption is ~100 m³ year^-1. A storage system of about 35 m³ collects rainwater in periods of high rainfall, to be used in period of little rainfall.

Figure 3. Use of treated rainwater.

Consumption Reduction System

Simple technical solutions allowing water consumption reduction, with the same comfort and performance, are implemented. The main equipments applied are: (a) toilet flushing, operating with cisterns (with dual discharge volume) of only 3.5 L versus the traditional cisterns of 9 L; (b) water taps with two possibilities of water flow rates (5 and 10 L/minute), provided with Venturi diffusers that allow washing with lower water flow by mixing air to water (due to higher water velocity); (c) washing machines using 60 L/cycle versus 100 L/cycle for traditional cloth washing, (d) dish washers using 14 L/cycle versus 20 L/cycle for traditional dish washers.

In order to stimulate waste reduction suggestions are made to users, like: watering the garden in the evening when the temperature is not high, etc.

Photo2. Filter.

Separated Network System

Differentiated water distribution and discharge systems are adopted; i.e.: the potable water network (distributing water into sinks, bath-tubs, showers, etc.) is separated from the “treated greywater” distribution network, and from the “treated rainwater” distribution network. There is no possibility of treated greywater and rainwater water drinking.

Table 1. Disinfectant dose.

Table 2. Parameters after treatment.

Figure 4. Consumption percentage.

Figure 5. Comparison.

RESULTS

The main results, obtained from Nov 2000 till Nov 2001, are reported below.

Table 1 shows the peracetic acid dose for a complete disinfection (faecal coliforms up to zero: see table 2). Figure 4 shows the consumption percentage in the flats. Figure 5 shows comparison between AP system consumption and the traditional one.

DISCUSSION

The potential water saving percentage of the proposed AP system compared to the traditional one is ~50% of potable water (see figure 5), of this: a) ~30% by means of components at low water consumption, b) ~15% by means of greywater reuse; c) ~5% by means of rainwater use.

Greywater coming from body washing (33% of total consumption in the flats) is enough to feed the 23% of toilet flushing consumption in the flats (see figure 4). Rainwater allows ~8% saving of the total consumption in the flats (see figure 4); treated rainwater use represents ~66% of total washing machine consumption.

CONCLUSION

Results show a valid possibility for drinking water saving (~50%) in households. Experimentation continuation will make it possible to obtain more data about sustainable development.

ACKNOWLEDGMENTS

The Partners wish to thank all the people and companies that have been working and co-operating in the AP.

PROJECT SECRETARIAT

ENEA (Italian National Agency for New Technologies, Energy and Environment) Section of Wastewater Treatment and Water Cycle; ENEA.PROT.IDR; B. Failla; Via Martiri di Montesole, 4; 40129 Bologna (Italy); Telephone +39 051 6098698; Fax +39 051 6098309; E-mail: failla@bologna.enea.it