Analysis of Reject Water Formed in the Mechanical Dewatering Process of Digested Sludge Conditioned by Physical and Chemical Methods

Abstract

Reject water separated from digested sludge may be a potential source of nutrients due to its high content. However, most often, reject water after sludge dewatering is directed to sewage lines at wastewater treatment plants, negatively affecting their operation, especially in the biological part. The activities related to sludge conditioning before dewatering have a direct impact on the quality of the reject water. The reject water of raw digested sludge is characterized by very high concentrations of ammonium nitrogen, at 1718 mgN-NH4+/dm3; phosphates, at 122.4 mgPO43−/dm3; and chemical oxygen demand (COD), at 2240 mgO2/dm3. The objective of the research was to determine the impact of selected sludge conditioning methods on the quality of reject water obtained after sludge dewatering. The following parameters were analyzed in the reject water: the chemical oxygen demand (COD), phosphates, ammonium nitrogen, and total suspended solids (TSS). It has been observed that the sludge sonification process increases the content of impurities (COD, phosphates) in reject water with an increase in the amplitude of the ultrasonic field. On the other hand, the chemical reagents cause a decrease in the concentration of the pollutants with an increase of the chemical dose. It has been found that the inorganic coagulant PIX 113 gives much better results regarding the reduction of contamination than the polyelectrolyte Zetag 8180.

Possibilities of Managing Waste Iron Sorbent FFH after CO2 Capture as an Element of a Circular Economy

“…In the case of combinations E and F, where elemental sulfur was added to the samples, the filtrate was most contaminated with suspension and dissolved substances. The characteristics of the filtrate, regardless of the combination used, indicate that it must be subjected to further purification and/or recovery, similar to the filtrate from sludge dewatering [55]. The filtrate after the solid-liquid separation process was also assessed for the presence of iron and sulfur compounds as a potential mineral waste coagulant (iron sulphate), (Table 10).…”

“…In the case of combinations E and F, where elemental sulfur was added to the samples, the filtrate was most contaminated with suspension and dissolved substances. The characteristics of the filtrate, regardless of the combination used, indicate that it must be subjected to further purification and/or recovery, similar to the filtrate from sludge dewatering [ 55 ].…”

Application of Advanced Oxidation Technology in Sludge Conditioning and Dewatering: A Critical Review

“…The anaerobic fermentation treatment of the excess sludge after ozone treatment can strengthen the anaerobic fermentation speed and increase biogas production, which has a significant effect on the energy conversion and reduction of sludge [ 51 ]. However, high ozone dose or long pretreatment time will lead to mineralization of dissolved organic matter and inactivation of key microorganisms, which is not conducive to methane production and energy recovery [ 52 ]. High cost is the main obstacle restricting the engineering application of ozone sludge treatment.…”

Adaptive Fuzzy Control of Sludge Conditioning and Pressing

“…A filter cloth is sandwiched between each group of filter plates and filter frames, and the filter plates and filter frames are pressed tightly with the movable end, so that a filter press chamber is formed between the filter plates and the filter frame. The sludge flows in from the feed liquid inlet, and the water flows through the filter plate out from the filtrate discharge port [17]. During this procedure, the filter cake will be squeezed and accumulated on the frame filter cloth.…”