Siphon type composite vertical subsurface flow constructed wetland

A siphon type composite vertical subsurface flow constructed wetland, comprising:

• an uplink pool and a downlink pool, a depth of the uplink pool being ¾ of a depth of the downlink pool;
• siphon type drain tubes equidistantly distributed at a first outer side of the uplink pool driven by a depth difference between the uplink pool and the downlink pool, a total flow through the drain tubes being greater than a total influent flow;
• and
• three layers of substrates on the uplink pool and the downlink pool, from top to bottom, a substrate on a first substrate layer being a biological ceramsite, another substrate on a second substrate layer being zeolite, a further substrate on a third substrate layer being cobblestone;
• the first substrate layer and the second substrate layer of the downlink pool and the first substrate layer and the second substrate layer of the uplink pool being separated by barriers, the third substrate layers of the downlink pool and the uplink pool being integrally communicated, and sewage in the downlink pool being configured to flow to the uplink pool through a communication port;
• and
• wherein:
• the biological ceramsite has a grain size smaller than that of the zeolite;
• the zeolite has a grain size smaller than that of the cobblestone;
• the first substrate layer comprises aerobic microbes adhered thereto for an aerobic sewage treatment;
• at least one part of the first substrate layer is always in air;
• and
• the siphon type drain tubes are configured to discharge sludge in the third substrate layer along with water.