Circulating pump unit of sewage suction truck

The utility model discloses a circulating pump unit of a suction-type sewer scavenger, which belongs to the technical field of sanitation trucks and is formed under the combined action of a sewage tank body, a circulating pump body, a first pipeline, a second pipeline, a third pipeline, a purification box, a fourth pipeline and a fifth pipeline so as to realize the effect of sewage circulating treatment. Meanwhile, the effect of recycling the sewage is also achieved, and water resources are greatly saved; a first filter layer, a second filter layer and a third filter layer are arranged in the purification box, so that the effect of purifying sewage is achieved, the situation that the sewage pollutes the environment when being discharged is avoided, and the effect of environmental protection is achieved; the first one-way valve and the second one-way valve are arranged at the inlet end of the third pipeline and the inlet end of the fifth pipeline respectively, so that the sewage recycling effect is achieved un