Run off surface waters

Oil traps and separators

Oil traps are used for treating wastewaters containing oils that originate from residential, industrial or crafts areas, such as garages, squares, parking lots, mechanical workshops, vehicles washing plants, etc., before being discharged into the public sewage or before being treated in an appropriate purifying plant (pressurized filtration, chemical-physical treatment, etc.).

Sand traps are used for separating sands and inert particles present in wastewater.

Oils separation is a physical removal process of all substances having a specific weight inferior to water. Sand and inert particles separation is also a physical process, but it removes all the substances having a specific weight superior to water.

Oil traps are decantation tanks equipped with an internal section, where oils float to surface by means of physical liquid/liquid separation mechanisms. Separated substances are trapped into the internal section, while purified waters flows to the main compartment through a specific passage at the bottom of it, and then to the exit.

Sand separators are decantation tanks in which sands and inert particles settle to the bottom.

These items may be integrated with pre- and post- treatments that allow to improve the total purification efficiency, depending on incoming wastewater features and final discharge type.

Oil traps and separators are particularly suitable to small and medium households communities, as they offer the following advantages:

• They simplify the treatment process, by consequently reducing the number of parts, thus the necessary investment.
• They are very easy to manage and maintain.
• No electric consumption.

First flush rainwater treatment plants

In the last years it has become more and more important to correctly manage the rainwater washing paved surfaces; this is a key matter in any environmental protection project of urban areas. The best solution to this problem is having a multidisciplinary approach which involves technical, social and economic sides.

The big urban expansion of the last decades has created new waterproof areas and an extension of the existing ones; this has consequently reduced the natural aquifers renewal and has generated a proportional increase of the water flow rates in the urban areas. This involves a strong impact on rainwater quantity and quality. These waters have to be duly purified and correctly discharged in drainage networks and water streams, which are often not sufficient to receive the surplus flow.

First rainwaters usually correspond to a 5 mm rainfall in the first part of every meteoric event, evenly spread on the whole draining surface served by the rainwater collection network. At first these waters are collected in a storage section, then they are automatically conducted to treatment plants that purify them, in order to comply with required qualitative standards – in Italy as per Appendix 5 of the national law D. Lgs. 152/06.

Rainwater recovery plants

Recovery and reuse of rainwater coming from roofs and coverings.

Water is a precious and free resource. About 50% of the daily water needed in residential buildings (corresponding to a per-capita request between 150 and 200 liters) may be obtained by rainwater recovery, which can be used for green areas watering, vehicles washing, WC cisterns filling and laundry washing.

By multiplying the recovered rain water volume for the cost of potable water, it can be easily calculated the economic saving obtained by not having used the aqueduct potable water.

Italian financial law of 2008 – Law 244/2007, clause 1, paragraph 288 – declares that starting from 2009 the release of a building permission is subjected, in addition to the building energetic certification, also to its structural characteristics, aiming at water saving and rainwater reuse.

Some Italian regions have already issued specific laws, i.e. Lombardy, Tuscany, Marche, Lazio, Puglia, Umbria, while others are in their issuing phase.