SCHEMES OF CONNECTION OF RAIN GARDENS TO DRAINAGE NETWORKS

Abstract

Based on existing technologies for accumulation, temporary retention, and filtering of surface runoff, 3 schemes for connecting rain gardens to storm sewer networks are proposed and the shapes of hydrographs for a specific scheme are substantiated.

According to scheme № 1, the entire volume of rainwater with a flow rate Q_д enters the rain garden. This scheme is used in cases where the rainwater is conditionally clean, for example, runoff from the surface of roofs, from improved surfaces on which there is no traffic and there are no other sources of pollution. For this scheme, the inflow of rainwater to the rain garden Q_en coincides with the hydrograph of rainwater: Q_en=Q_д.

According to scheme № 2, the polluted part of the runoff with a flow rate Q_оч enters the facility's drainage system or directly to the treatment facilities, and the conditionally clean runoff with a flow rate Q_en enters the rain garden. In this case, the overflow flow rate Q_пер can be discharged back into the network or into the nearest ravine, depression, etc. Accordingly, for this scheme, the inflow of rainwater to the rain garden is:

– at Q_д<Q_оч:

Q_en =0;

– at Q_д >Q_оч:

Q_en =Q_д–Q_оч.

where Q_оч – treatment flow, i.e. the flow of contaminated wastewater that requires treatment.

According to scheme № 3, the polluted part of the runoff from the runoff basin first goes to local treatment facilities, and then is fed into the rain garden. The advantage of this scheme is the possibility of installing an autonomous surface drainage system. This scheme also allows for the fullest use of the rain garden's post-treatment function without the risk of groundwater contamination and without clogging of the garden's filtration and drainage loading. For this scheme, the inflow of rainwater to the rain garden is:

– at Q_д<Q_оч:

Q_en =Q_д ;

– at Q_д> Q_оч:

Q_en =Q_оч.

Compared to scheme No. 1, schemes No. 2 and No. 3, under the same conditions, have smaller calculated areas of the filter bed.