Pulp Paper & Logistics
KEMIRA 27
represents the percentage of bioreactor solids that are active microorganisms. Maximizing the ABR provides many benefits such as enhanced sludge quality and improved settling. ABR is calculated through the ratio of AVSS to Total Suspended Solids (TSS).
• Specific Floc-Bulking ATP (s-fbATP) – represents the quantity of ATP from bulking floc relative to microorganisms. This measurement has been shown to provide early-warning of bulking conditions, allowing operators the ability to proactively identify bulking conditions. The fundamental reason for this approach being a common practice is that the conventional indicator of biomass quantity (Mixed Liquor Suspended Solids, or MLSS) and (Mixed Liquor Volatile Suspended Solids or MLVSS) are unable to distinguish between living, dead, or biologically-inert solids. With no way to be certain of the quantity of living biomass, operators must maintain a high MLSS and inventory to ensure sufficient treatment capacity. There are various downsides to this approach, which include: • Starvation: ‘sluggish’ biomass performs at less than peak efficiency. This can occur when the plant has accumulated too large a biomass population or if the plant experiences low flows and/or a drop in available food. • Poor settling: along with starvation, high total solids inventory creates competition and results in advantages for filamentous microorganisms (which are a major oxygen consumer). • Increased waste biomass: to offset new growth and maintain recycle rates, Waste Activated Sludge (WAS) flows must increase
to accommodate higher solids inventory, meaning more waste biosolids requiring disposal. • Poor mass transfer: increased solids concentration creates additional resistance to mass transfer for aeration, decreasing efficiency and increasing power requirements. • Increased pumping: increased solids loading creates additional wear on pumps and requires more dewatering, thereby increasing energy input requirements. • Aerobic digestion: increasing solids concentration increases the
possibility of aerobic digestion of old or dead biomass waste water constituents that are difficult to degrade. In addition, digestion of old biomass consumes costly process additives such as oxygen and nutrients, and even results in the release of nutrients to the effluent.
Daily measurements of AVSS
can be used to quantify the living biomass in the process and confirm the presence of sufficient biomass to degrade the waste water constituents entering the process each day. Purging
the system of solids will allow living biomass to re-populate the process to create greater efficiency, resulting in sufficient Active Volatile Suspended Solids (AVSS mg/L) and Active Biomass Ratio (ABR%) levels to treat the incoming waste water. Each plant has its own specific
requirements, and Activated Sludge Process Biomass Inventory needs to be set to the proper level to meet the process configuration and gain on efficiency and cost of operation. Kemira says that the LumiKem Wastewater technology, combined with its waste water sofware package Portal G2, provides access to a ground-breaking new tool that delivers significant benefits for the operation by predicting upset, managing causes and effects, managing energy costs and much more. More information from Mats
Rönnbäck, Snr Vice President, Global Marketing and Business Development, Kemira, Helsingborg, Sweden. Tel: 46 737 191 606.
www.kemira.com
May 2013
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