J. Huesa successfully completes the commissioning of an industrial wastewater treatment plant for a leading multinational in the sale of pulses that is immersed in an expansion of its factory to accommodate a new line of cooked pulses.
Once the analytical parameters of the starting water had been analysed, together with the current and future requirements of our client, the technical team of J. Huesa, together with the specialist team of the industrial company, got down to work on the customised design of an aerobic biological purification system, which is detailed below.
Data and water properties
As the owner is entering a new market, he is not clear on how he will operate the production plant, which will affect the quantity and quality of the discharges generated, which is why one of the starting requirements for the planned facility is that it can accommodate future expansions if necessary.
Raw water characteristics:
The objective of the WWTPi is that the clarified wastewater complies with the discharge parameters
The main data of the system implemented, which consists of an aerobic biological treatment system of the SBR (Sequential Biological Reactor) type, are detailed below. This technology integrates the biological reactor and the decanter in the same tank, so that the system operates by means of treatment batches developed over time in stages, with the clarification of the mixed liquor being one ofthe stages of the process.
The discharge from the factory is collected in a civil works well in which a pumping system has been installed, with a back-up pump. The pumps are designed to withstand a peak flow of 20 m3/h.
To prevent malfunctioning and clogging of coarse solids, a roughing screen has been installed to retain the coarsest solids (> 1mm).
The roughing system prior to the homogenization tank consists of a rotary sieve. Self-cleaning device, capable of operating for long periods of time without the need for extensive maintenance.
Rotary Sieve Detail
The solid particles are retained on the surface of the screen and are conveyed by the scraper, which is responsible for separating them and depositing them on an inclined tray to fall by gravity, and are subsequently collected in a container for their management.
The next step in the treatment line is a homogenization tank, which is equipped with a coagulant dosing system to reduce phosphorus. To counteract the acidification of the mixed liquor, a soda dosing system is included. A pH meter is installed to monitor this parameter at all times.
The homogenization tank has a double function: on the one hand, to homogenize the flow to avoid contamination peaks and to have space to store spillage in case of failure of one of the main components of the system. Two days of retention time have been considered.
In addition, to prevent anaerobic conditions from occurring, a submerged radial aeration system has been installed.
Aerobic Biological Treatment type SBR
The objective of biological water treatment is the reduction of organic matter and the elimination of non-sedimentable colloidal solids using microorganisms. In conventional biological treatment, there are at least two distinct stages: firstly, the biological reactor in which the organic matter meets the microorganisms that eliminate it, and then a clarification process in which the biomass or sludge is removed from the treated effluent, normally by decantation.
Depending on the nature of the organic matter present in the effluent to be treated, the use of oxygen may or may not be necessary for its metabolization.
The SBR type biological reactors differ from conventional treatments in that they integrate the biological reactor and the decanter in the same tank, operating the system by means of treatment batches developed over time in stages, with the clarification of the mixed liquor being one of the stages of the process, obtaining two advantages over the conventional system such as the reduction of the space occupied by the installation and increased flexibility of the aeration – anoxia processes necessary for the elimination of nitrogen.
A SBR such as the one installed at our customer can divide its operation into operating cycles in which the following phases can be distinguished:
- Filling: fundamental phase of the process in which the feed rate, the volume to be maintainedin the tank and the concentration of the reactor play an important role.
- Reaction: Occurs simultaneously with the previous phase; in this phase the reactor conditions (anoxic, anaerobic, and aerobic phase) that facilitate the elimination of organic matter and nonsedimentable solids are realized.
- Resting/decanting: After the reaction, a reactor rest stage is necessary to favour the gravity settling of the micro-organisms inside the reactor.
- Emptying: the discharge is evacuated on the surface of the reactor, since the clarification of the mixed liquor that takes place in the previous phase remains on the surface of the reactor.
- Purging or emptying of excess sludge produced in the biological reactor.
- The following measuring elements have been installed to ensure the correct operation of the SBR:
- Tank level meter, a key piece that regulates the operation of the different stages that take place in the SBR tank.
- Redox and pH meter, necessary to know the redox potential of each of the reactor phases and to optimise the nitrification/denitrification processes, as well as to control the reactor aeration system.
- Aeration system consisting of a grid of diffusers distributed over the entire surface of the reactor. This aeration system is the most efficient alternative for aeration in biological systems.
- Agitation system, which complements the aeration system by means of a submersible propeller agitator that allows the development of anoxic phases that guarantee denitrification.
The sludge produced in the SBR tank is pumped by means of a centrifugal pump into a conical sludge accumulation tank with a capacity of 15 m3. The internal sludge removal system in the reactor tank is arranged in such a way that large quantities of sludge can be pumped out in one go. In this way, longer concentration and thickening times are used before purging, reaching higher concentrations and thus reducing the amount of sludge to be managed.
Instrumentation and control
The WWTP is equipped with instrumentation and control elements (automatic valves, pressure switches, pressure transmitters, flow meters, conductivity and pH meters…) which communicate with the programmable logic controller, included in the control panel, through IO-Link technology.
The control panel also includes a touch screen for the operation and configuration of the plant. J. Huesa’s Instrumentation and Control team has designed the control panel so that it can be integrated into the customer’s SCADA system. It also includes a remote-control system.