Wastewater Solutions

Deploying new WWTP technologies while generating renewable energy sources and gas from waste materials

Why Texzon Utilities for Waste Water Infrastructure?

Why it is important

Wastewater operations are typically the largest energy expense in a community, and reductions in energy usage can yield significant environmental, economic, and social benefits for these communities. Across the country, municipal wastewater treatment plants are estimated to consume more than 30 terawatt-hours per year of electricity, which equates to about $2 billion in annual electric costs. Electricity alone can constitute 25% to 40% of a wastewater treatment plant’s annual operating budget and make up 15% to 30% of a given municipality’s total energy bill. These energy needs are expected to grow over time, driven by population growth and increasingly stringent water quality requirements. Moreover, wastewater contains about five times more energy than is needed for its treatment in terms of untapped thermal energy, which can be captured and used to generate energy.

Wastewater facility retrofits can yield up to 50% in energy savings and 30% on average. In recent years a growing number of utilities responsible for clean water have been moving from strict wastewater treatment to water resource management, some formally renaming themselves water resource recovery facilities. As wastewater facilities undergo this transition in equipment, processes, and operations, there are abundant opportunities to make energy efficiency retrofits. Facilities can expand this energy-efficient foundation with resource recovery measures to move closer to a sustainable wastewater infrastructure.

Wastewater & Agriculture

Agricultural and waste treatment professionals once accepted the high costs of operating wastewater and manure treatment facilities as a consequence of meeting their discharge permit requirements. As the cost of energy rises and emphasis on renewable energy increases, local authorities and municipalities are seeking solutions that save money and meet renewable requirements. Jenbacher gas engines provide a renewable energy solution through combined heat and power (CHP) technology that results in long-term savings for wastewater treatment plants. Alternatively, biogas upgrading plants can convert biogas to biomethane for injection into the gas grid or for vehicle fuel.

Wastewater Treatment Energy Costs

Waste treatment processes include energy-intensive operations such as aeration and pumping. As a result, wastewater treatment plants (WWTPs) require significant energy consumption. As electrical prices increase, plant operators are facing higher energy costs in order to meet discharge permit requirements. The second leading expense to WWTP owners is the cost of energy, behind only personnel. For plants, who employ anaerobic digestion for biosolids treatment, the process of combusting digester gas to produce electricity and heat through cogeneration/CHP may provide a solution to rising operational costs.

A large proportion of the world’s sewage systems do not recover value from the sewage in the form of electricity and heat. But the renewable energy fuel source derived from sewage gas can be converted using reciprocating gas engines, to electricity and heat, offsetting as much as two-thirds of a plant’s electricity demand and eliminating the need to purchase fossil fuels for plant heating processes.

Benefits of CHP and Wastewater Treatment Facilities

Generation of renewable energy from a waste material through cogeneration / CHP
Reduction in carbon emissions especially compared to aerobic sewage treatment
Economical onsite electrical power production and reduced transmission losses
Production of a low-carbon fertilizer / soil improver
Cost effective, proven technology

Biogas from Waste Disposal

Treatment of biological waste represent a major challenge for municipalities. For a wide range of organic substances anaerobic digestion is a superior alternative to aerobic designed systems which releases methane into the environment. Biogas – a mixture of both methane and carbon dioxide – is created during anaerobic digestion of bio-waste and slurry and serves as a high-energy renewable fuel that can be used as a substitute for fossil fuels. Biogas-fueled gas engines improve waste management while maximizing the use of an economical energy supply.

Biogas Creation

Biogas results from anaerobic fermentation of organic materials. As a metabolic product of the participating methanogens and acidogenic bacteria, the prerequisites for its production are a lack of oxygen, a pH value from 6.5 to 7.5 and a constant temperature of 35-45°C (mesophilic) or 45-55°C (thermophilic). The digestion period or retention period is typically between 10 and 30 days depending upon the type of digestion employed. The anaerobic digestion systems of today operate largely within the mesophilic temperature range.

Conversion Steps from Waste to Power

The process of biogas generation is divided into four steps: 1. Preparation of the input waste material – including removal of physical contaminants, particle size reduction & pasteurization 2. Digestion (fermentation), consisting of hydrolysis, acetogenesis, acidogenesis and methanogenesis 3. Conversion of the biogas to renewable electricity and useful heat 4. Post-treatment of the digestate Initially the feedstock to the digesters is received in a primary pit or liquid storage tank. From here it is loaded into the digester by various means depending upon the constitution of waste materials. In the digestion tanks a series of biological processes are harnessed in order to produce biogas. Hydrolysis is the process where the organic material is solubilized into the digestion liquid. It then undergoes the intermediate steps of acidogenesis and acetogenesis which create the precursor molecules for methanogenesis. Methanogens feed off these precursors and produce methane as a cellular waste product. The biogas containing this biologically-derived methane is contained and captured in a gas storage tank which is located separately to the main digester, or alternatively can form its roof. The gas storage tank acts as a buffer in order to balance fluctuations in the production of gas in the digester.