Don't reject the idea of treating reject water

Abstract

Separate treatment of sludge liquor (reject water) is a promising alternative for conventional biological extension of sewage plants with sludge digestion. Treatment of this nitrogen-rich water may significantly save in cost as well as in area demand. This article evaluates pilot plant investigations of five treatment options: the biofilm airlift suspension reactor, the membrane bioreactor, the bioreactor without sludge retention, stripping of ammonia (both airstripping and streamstripping) and the MAP/CAFR-process. The choice of the optimal treatment method is dependent on site-specific factors. This is demonstrated by two case studies.

Development of a bio-zeolite fixed-bed bioreactor for mitigating ammonia inhibition of anaerobic digestion with extremely high ammonium concentration livestock waste

“…Removing ammonia during the anaerobic digestion has attracted considerable interest in recent years. Many physicochemical and biological methods have been developed to alleviate the inhibition of ammonia, such as ammonia striping [7,8], adding ammonia-adsorption materials [9][10][11], struvite precipitation [12,13] and anaerobic ammonia oxidization [14,15]. However, since their complex process, low efficiency and high operation costs, these methods are usually unsatisfactory to the practical application for ammonia removal.…”

Biomass production and nutrient removal by Chlorella sp. as affected by sludge liquor concentration

“…The reject water derived from the dewatering process of anaerobically stabilized sludge, sludge liquor (SL), has a concentration of nitrogen in the order of 1000 mg L À1 , high chemical oxygen demand (COD), and high total suspended solids (TSS) content (Davis and Masten, 2009). The SL is usually returned to the head end of the WWTP and accounts for 15e25% of the total nitrogen load at the WWTP (Fux et al, 2006;Janus and van der Roest, 1997). Algae could potentially be integrated at a WWTP to treat the side-stream of SL and offers the combined benefits of nutrient removal, energy production, and CO 2 sequestration (Rusten and Sahu, 2011;Sahu et al, 2013;Yuan et al, 2012).…”

The removal of phosphate from wastewater using anoxic reduction of iron ore in the rotating reactor

“…The concentration of phosphorus in municipal wastewater is from 5 to 20 mg/L; meanwhile the concentration of phosphorus in reject water is up to 130 mg/L [2]. Although the flow of reject water is only 2% of the raw sewage flow [3], it contributes from 10 to 80% of phosphorous load on the activated sludge tank [4]. Therefore, the removal of phosphorus from reject water can significantly reduce the phosphorus load to the main stream of the MWWTPs.…”