Global Water Engineering has partnered with Chokyuenyong Industrial in Thailand to cut effluent COD pollution levels at its cassava production plant by more than 95 percent while extracting gas from its wastewater to power its boilers and generate electricity for its own use and to sell back to the provincial grid.
Processing 1,200 tons of cassava roots a day, Chockyuenyong Industrial, headed by Tawatchai Yuenyong, uses GWE anaerobic technology with a capacity of 3,200 m3 effluent a day. The installation provides wastewater cleanliness while generating green power and carbon credit profits as well.
Commissioned and refined over the past three years, the Chockyuenyong installation:
- Cut the Chemical Oxygen Demand (COD) pollution level of influent wastewater from 22,500 ml/l (14,525mg/l Biochemical Oxygen Demand, BOD O2) to less than 1125 mg/l, resulting in substantially cleaner discharges to treatment ponds and ultimately the environment.
- Returns up to 2.7 Mw of electricity a year to a provincial power grid, PEA, which serves some areas distant from major generating sources and welcomes fresh input of green power generated locally.
- Saves the equivalent of up to 21,000 liters a day of fuel oil by producing up to 34,000 Nm3 of bio gas, which is used to power the boilers and heating equipment used extensively in cassava drying and processing and to generate electricity for the large amounts of rotating equipment used in processing.
- Generates carbon credits under the United Nations’ Framework Convention on Climate Change, through which it earns valuable internationally tradable CER certificates, representing the right to emit one ton of carbon dioxide or carbon dioxide equivalent.
Chokyeunyong’s process involves an equalization basin (total volume 1600m3) with submerged agitators, degasifying basin with agitator (24 m3) in-line pH adjustment, NaOH storage tank (25m3) UASB methane reactor (active volume 4800 m3) and biogas flare (standby, for use if required). The technology is all above-ground for simplicity and ease of maintenance.
GWE’s anaerobic treatment significantly reduces the plant’s carbon footprint by avoiding the release of methane gas into the atmosphere. The wastewater passes through several pre-treatment steps before entering a GWE methane reactor in which the wastewater’s organic content (COD) is digested by bacteria in a closed reactor, degrading the compounds and converting them into valuable biogas and cleaned effluent.
Biogas from the process is collected and reused as renewable fuel in the plant’s thermal oil boiler, saving money that would otherwise be spent on bunker oil.Chokyeunyong’s excess biogas is used in electrical power generation.
Results achieved at Chokyeunyong can be even further improved by converting its solid wastes (residual pulp from the roots, after starch extraction) into biogas as well, using GWE’s RAPTOR™ treatment system for solid organic residues, says GWE.
Its RAPTOR technology stands for Rapid Transformation of Organic Residues. It’s a powerful liquid-state anaerobic digestion process that consists of enhanced pre-treatment followed by multi-step biological fermentation to optimize conversion of almost any organic residue or energy crop into biogas, valuable electricity or heat.
Chokyeunyong Industrial President Tawatchai Yuenyong says his company’s investment program has been well justified by the outcome in terms of environmental and financial results and as a good neighbor in the local community. “Our investment program has had a very happy ending,” he says.