NEXOM provides reliable and cost-effective solutions for water and wastewater treatment with a specific focus on OPTAER® lagoon based processes. Our extensive research and development in cold temperature technologies, and experience in pond and lagoon based project applications, has provided a level of technical understanding of these processes that is second to none.
We specialize in the optimization and restoration of existing water and wastewater treatment infrastructure. More than simply an equipment manufacturer, we are a complete solution provider, striving for 100 percent customer satisfaction by offering a diversified mix of expertise, methodologies, and technologies.
NEXOM is dedicated to the development of integrated wastewater treatment technologies and designs that maintain the low capital and operation and maintenance costs of the original stabilization and aerated lagoon concepts, while achieving the effluent quality performance of “high-tech” advanced treatment facilities.
Since 1997, we have completed more than 200 water and wastewater treatment projects with more than 95 percent of those projects are completely “turn-key” including design, equipment supply, and installation.
Nitrification & BOD/TSS Reduction
Total ammonia in wastewater is comprised of un-ionized ammonia (NH3) and ionized ammonia (NH4+). The ratio of un-ionized to ionized ammonia is a interrelation of pH and temperature. The un-ionized portion is toxic to fish at low concentrations, and wastewater treatment systems that discharge to flowing streams typically have ammonia or toxicity limits to protect fish living in the receiving stream.
Decreasing the toxicity of wastewater effluent can be accomplished in part by decreasing the temperature of the effluent or by reducing the pH. In most cases temperature and pH manipulation are not viable and the toxicity must subsequently be lowered by the reduction of total ammonia through nitrification.
Lagoon or pond based treatment systems provide some ammonia removal capability during the summer months, but are generally incapable of meeting current standards during prolonged periods of low water temperatures. The problem with nitrification in cold climate lagoons is two-fold:
- Nitrifying bacteria, Nitrosomnas and Nitrobacter, are generally not able to compete with heterotrophic bacteria in high BOD wastewater, so nitrification is easiest to accomplish near the back end of a lagoon system once BOD has been reduced to below 30 mg/l.
- In cold climate winter conditions, the lagoon water temperature near the back may be below 1°C. Nitrifying bacteria are very temperature sensitive, resulting in reduced (negligible) treatment rates as water temperatures drop below 5°C.
Nitrification (ammonia conversion to nitrates) in the OPTAER® system is performed by the SAGR®. The SAGR® is ideally suited for post lagoon nitrification in severe cold to moderate climates where water temperatures can be below 0.5°C for extended periods of time.
The SAGR® can be combined with aerated or facultative lagoons to meet effluent ammonia requirements in systems that operate as continuous discharge or controlled discharge.
Extensive data collected from demonstration facilities in Steinbach, Manitoba and Lloydminster, Saskatchewan shows that the SAGR® can reliably nitrify lagoon effluent year round consistently meeting effluent levels of <1.0 mg/l. SAGR® systems in cold climate areas across North America are allowing communities to meet their new ammonia and toxicity limits without abandoning their existing lagoon infrastructure.
Total Phosphorus Removal
Phosphorus is known to have a deleterious effect (eutrophication) on receiving bodies of water and is typically the limiting nutrient for algae growth in lakes and streams. The algae blooms reduce the recreational value of the lake, cause odors and consume dissolved oxygen during decomposition. Low dissolved oxygen levels stress higher aquatic life forms and in extreme cases cause fish kill. While there are many sources of phosphorus in water bodies, the contribution of soaps, detergents, and other phosphorus compounds in wastewater effluent cannot be ignored.
The Nelson Environmental Solution
OPTAER® Wastewater Treatment Facilities can be equipped with chemical addition systems prior to the final settling cells to bind and settle phosphorus.
Where lagoons discharge into especially sensitive receiving streams, phosphorus removal to lower levels may be required. A filtration system following the lagoon further removes chemical floc formed in the lagoons while additional chemical may be added to a contact chamber upstream of the filter to achieve lower effluent Total Phosphorus (TP) levels.
A Ferric Chloride addition system can be used in combination with a gravity sand filter to achieve high levels of phosphorus removal. The system includes a serpentine contact chamber, which leads into an upflow gravity sand filter. In the filter, phosphorus is removed from the effluent by adsorption to the hydrous ferric oxide coated filter media. Rejected solids are recycled to the primary cell of the OPTAER® wastewater treatment lagoon where the precipitated phosphorus and iron settle out.
Alum addition in ponds with adequate settling time can reduce TP levels to 1 mg/l. Adding filtration after the settling ponds with secondary Alum addition can reduce TP levels to levels as low as 0.5 mg/l.
A gravity sand filter equipped with a ferric addition system following an OPTAER® lagoon process can achieve effluent total phosphorus levels of less than 0.02 mg/l. Filter reject is generally returned to the lagoon. Settling cells are typically designed to provide 10 to 20 years of sludge storage prior to de-sludging.
Raw Water Reservoir Aeration
Raw Water Reservoirs (RWR) store water prior to passing it through a potable water treatment plant. In many cases, water quality in the raw water reservoirs is poor since surface runoff with high levels of dissolved organics, iron, and manganese, is the typical water source. These contaminants cause a brownish water color (staining) and contribute to undesirable taste and odor. Anaerobic decomposition of settled organic material generates Hydrogen Sulfide (H2S), creating a “rotten egg” taste and odor in raw water sources while increasing treatment plant chemical usage demand.
Natural atmospheric aeration in a reservoir only provides oxygenated conditions to a depth of 2 to 3 m during ice free conditions. In areas where ponds freeze over, there is no opportunity for surface re-aeration during cold periods. Typically, water intakes are located close to the bottom of the reservoir, where dense, poor water quality resides due to thermal stratification. The lack of dissolved oxygen also causes the release of phosphorus from anoxic sediments, encouraging algae growth and causing oxygen depletion during biodegradation. This further contributes to poor taste and odor.
Fine Bubble Aeration: The LINEAR fine bubble aeration diffusion tubing is laid on the bottom of the raw water reservoir to induce complete circulation and introduce oxygen at the sludge water interface. Systems are designed to turn over the water in the reservoirs multiple times per day to disrupt the formation of thermoclines and anaerobic zones. The overall aeration intensity is low so that it does not roil up the sludge and subsequently increase suspended solids.
Dissolved Oxygen: Dissolved oxygen reacts with the soluble iron and manganese in the water column creating a precipitate that settles to the bottom of the reservoir. Increased oxygen levels prevent bottom waters from becoming anoxic thus reducing the release of iron, manganese, and phosphorous from accumulated sediments back into the water column.
Oxidation eliminates undesirable tastes and odors that emanate from anaerobically decaying organic matter. It also provides useful food to support a mix of organisms that compete with undesirables, such as algae, for available nutrients.
Destratification: Destratification results when “good” and “bad” water layers are eliminated, converting the entire body of water to fully oxygenated conditions. Bottom intakes are no longer a problem as water quality is uniform throughout the pond and reservoir temperatures are equalized through destratification. Cooler water is mixed to the surface resulting in reduced algae growth and evaporation.
Aeration and mixing to destratify a reservoir will maintain dissolved oxygen levels above the 5 mg/L required to effectively reduce TOC levels and the formation potential of THMs. Conditions stressful to algae (high-light intensity and high-dissolved oxygen) can force algae into a photorespiratory state, thereby reducing THM formation potential.
LINEAR diffuser tubing is composed of a virgin low density polyethylene (LDPE) containing >2% Carbon Black for UV resistance. An encapsulated ballast keel is located at the bottom of the tubing eliminating the need for concrete or steel weights.
Surgically produced die-cuts (air releases) in the tubing require 14 kPa (2 psi) more than hydrostatic pressure to allow air to pass through. The die-cuts act as valves throughout the life of the system, ensuring that:
- The diffusers emit a uniform air pattern even if the pond bottom is not perfectly level. Bottom elevation variations of up to 0.5m (1.5 ft) will not compromise the bubble pattern.
- If airflow is interrupted, the die-cuts act as one-way valves allowing water but little or no solids to enter the diffusers.
Treating water biologically by aerating a raw water reservoir is good environmental stewardship; as treatment plant chemical usage is significantly reduced from levels normally required to treat the water. Much of the organic, iron, and manganese removal occurs in the reservoir itself prior to reaching the water treatment plant.