Solutions for energy recovery from wastewater and organic waste

From May 30 to June 3, the sales team of bio­gas spe­cial­ist Wel­tec Biopow­er will be avail­able in Hall A4, Stand 217, to answer all ques­tions relat­ing to the con­struc­tion and retro­fitting of anaer­o­bic ener­gy plants: The range includes proven process­es from the field of bio­gas tech­nol­o­gy. The high sav­ings poten­tial of these process­es is demon­strat­ed by the mod­ern­iza­tion of the munic­i­pal waste­water treat­ment plant in Bücke­burg, Ger­many, which serves 33,000 inhab­i­tants. Since Wel­tec Biopow­er switched to anaer­o­bic sludge sta­bi­liza­tion in 2021, oper­a­tion of the plant at full load has become sig­nif­i­cant­ly more economical.

As gen­er­al con­trac­tor, the com­pa­ny was respon­si­ble for the con­struc­tion of the waste­water treat­ment sys­tem at the munic­i­pal sewage treat­ment plant. In addi­tion to the earth­works, the con­struc­tion of the foun­da­tion and the elec­tri­cal cabling, the work includ­ed the con­struc­tion of a new sta­t­ic sludge thick­en­er, a machine room for the com­bined heat and pow­er plant, the con­trol and pump­ing sta­tion, and a stain­less steel digester with a gas stor­age roof. Thanks to anaer­o­bic waste­water treat­ment, the sludge vol­ume has dropped by 35 per­cent, result­ing in a sig­nif­i­cant reduc­tion in trans­port and dis­pos­al costs. In addi­tion, the digester gas pro­duced can now gen­er­ate around 465,000 kWh of elec­tric­i­ty at full load. This allows the oper­a­tor to meet about 40 per­cent of its elec­tric­i­ty needs and save two-thirds of its elec­tric­i­ty costs.

“In view of the new green­house gas reduc­tion tar­gets and the sharp rise in ener­gy prices, an anaer­o­bic stage is an eco­nom­i­cal­ly attrac­tive solu­tion for waste­water treat­ment plant oper­a­tors, which also ben­e­fits from pub­lic sub­si­dies. Ulti­mate­ly, the com­bi­na­tion of waste­water treat­ment, pow­er and heat gen­er­a­tion, and cli­mate pro­tec­tion enables more effi­cient oper­a­tion, espe­cial­ly for small and medi­um-sized waste­water treat­ment plants.”

- Jens Albar­tus, Man­ag­ing Director

How these goals can be achieved with organ­ic waste is demon­strat­ed by a WELTEC plant in Pid­dle­hin­ton, south­west Eng­land. Here, a mix of food waste, expired food from super­mar­kets and organ­ic waste is fed to the bio­gas plant. In addi­tion to the sub­strate mix, the tech­ni­cal approach is also spe­cial. Before feed­ing and shred­ding, a de-pack­ag­ing machine sep­a­rates the food from the packaging.

Anoth­er effi­cien­cy bonus: The waste heat from the cogen­er­a­tion plant is sold to a near­by feed pro­duc­er, which also uses most of the elec­tric­i­ty. The bio­gas plant oper­a­tor feeds the excess elec­tric­i­ty direct­ly into the pow­er grid, gen­er­at­ing fur­ther rev­enue. The diges­tate from the process meets the require­ments of the British indus­try stan­dard PAS-100, so local farm­ers can use it as fertilizer.

Fol­low­ing a capac­i­ty expan­sion in 2014 from 20,000 t of sub­strate input per year to 30,000 t, the Group installed an addi­tion­al digester and stor­age tank, as well as Gas­Mix blend­ing sys­tems and a sep­a­ra­tion unit. A plant with this equip­ment would also sup­port the con­ver­sion to bio­methane production.