A unit (8) is intended for treating waste water. It includes a well (9) with an inlet conduit connector (21) and with an outlet conduit connector (22) at the outside of the well (9). The unit further includes a connecting conduit (20) inside the well (9). The connecting conduit (20) connects the inlet conduit connector (21) to the outlet conduit connector (22). There is at least one storage tank (13) inside the well (9) for a liquid chemical and a metering pump (18) inside the well (9) for pumping the chemical from the storage tank (13) into the connecting conduit (20). A control device (23) activates the metering pump according to a signal of a sensor (24) which senses a quantity of chemical element in the liquid flowing through the conduit (20).

A segment for an annular structure is disclosed. The segment includes an arcuate body extending between a first end and a second end. The segment includes a first plurality of interlocking portions extending from the first end and a second plurality of interlocking portions extending from the second end. Each interlocking portion includes a first leg and a second leg partially embedded in the arcuate body and a connecting portion connecting the first leg and the second leg, the connecting portion external to the arcuate body. The segment also includes a flange proximal to the first end and the second end of the arcuate body. Each flange includes a first spacing portion that extends radially outward from the outside surface and a second extending portion that extends distally from the main body portion.

A segment for an annular structure is disclosed. The segment includes an arcuate body extending between a first end and a second end. The segment includes a first plurality of interlocking portions extending from the first end and a second plurality of interlocking portions extending from the second end. Each interlocking portion includes a first leg and a second leg partially embedded in the arcuate body and a connecting portion connecting the first leg and the second leg, the connecting portion external to the arcuate body. The segment also includes a flange proximal to the first end and the second end of the arcuate body. Each flange includes a first spacing portion that extends radially outward from the outside surface and a second extending portion that extends distally from the main body portion.

An inner peripheral portion of a receiving frame and an outer peripheral portion of a lid body each include first and second surface parts. In the closed-lid state, the first surface part of the lid body is supported by the first surface part of the frame, each of which include a gentle gradient. The second surface parts of the lid body and the receiving frame are pressed against each other by a force caused by elastic deformation of at least one of the outer peripheral portion of the lid body and the inner peripheral portion of the receiving frame. The second surface part of the receiving frame includes a steeper gradient than the first surface part of the receiving frame by reducing its diameter toward a downward direction of the receiving frame.

An inner peripheral portion of a receiving frame and an outer peripheral portion of a lid body each include first and second surface parts. In the closed-lid state, the first surface part of the lid body is supported by the first surface part of the frame, each of which include a gentle gradient. The second surface parts of the lid body and the receiving frame are pressed against each other by a force caused by elastic deformation of at least one of the outer peripheral portion of the lid body and the inner peripheral portion of the receiving frame. The second surface part of the receiving frame includes a steeper gradient than the first surface part of the receiving frame by reducing its diameter toward a downward direction of the receiving frame.

A manhole base assembly and a method for making the same employ a non-cylindrical, low-volume concrete base that is fully lined to protect the concrete against chemical and physical attack while in service. This lined concrete manhole base assembly may be readily produced using a modular manhole form assembly which can be configured for a wide variety of geometrical configurations compatible with, e.g., varying pipe angles, elevations and sizes. The form assembly is configurable to provide any desired angle and elevation for the pipe apertures to interface with various underground systems, and can be formed on-site to facilitate compatibility with existing structures. The assembly provides for flexible, modular construction of a wide variety of lined manhole base assemblies at minimal cost, reduced concrete consumption and reduced operational complexity. The modular nature of the production form assembly also facilitates reduced inventory requirements when various manhole base assembly geometries are needed.

The present disclosure is generally directed to processes and apparatuses for use in forming one or more flow channels within a prefabricated manhole assembly. More specifically, an exemplary apparatus embodying various aspects of the disclosure may contain a rigid channel form with a closed top portion, a curved bottom portion, a first end, and a second end. The apparatus may also contain a bung(s) removably positioned into an exterior hole through a sidewall of the prefabricated manhole that may receive one end of the channel form, the bung(s) interior end may further have an open-ended U-shaped slot. A sliding wedge may be used to engaged/disengage the flow channel form.

The present disclosure is generally directed to processes and apparatuses for use in forming one or more flow channels within a prefabricated manhole assembly. More specifically, an exemplary apparatus embodying various aspects of the disclosure may contain a rigid channel form with a closed top portion, a curved bottom portion, a first end, and a second end. The apparatus may also contain a bung(s) removably positioned into an exterior hole through a sidewall of the prefabricated manhole that may receive one end of the channel form, the bung(s) interior end may further have an open-ended U-shaped slot. A sliding wedge may be used to engaged/disengage the flow channel form.

An oil and grit separator system having twin vortex which uses gravity providing a twin vortex effect to remove sediment and oil from contaminated water. The system is designed to control storm water runoff and reduce the annual suspended solids loading of the granulometric particles. The conception and configuration of the system has a double action vortex. It ensures an optimal treatment level in either light or heavy rain and avoids re-suspension of particles. It also removes, separates and stores floating oil without any possible re-suspension of the matter.

Disclosed herein is a free-standing cesspool and a cesspool liner that may be used to retrofit existing cesspools in order to provide additional storage and/or processing for raw sewage before the sewage leaches out of the cesspool.