Particulate Chemical Oxygen Demand Removal Research Articles

The Treatment Effect of Chemical Coagulation Process in South African Brewery Wastewater: Comparison of Polyamine and Aluminum-Chlorohydrate coagulants

An evaluation of a laboratory scale chemical coagulation using aluminium chlorohydrate (1%) and polyamine (1%) coagulants on its effectiveness in the removal of bulk inert pollutant contents such as particulate chemical oxygen demand (COD) and turbidity to obtain clean effluent discharge and most cost-effectively treated effluent using a jar test was conducted in this current study. This study aimed to find the viable inert removal coagulant between the two above-mentioned coagulants in order to achieve zero liquid effluent discharge (ZLED). The preliminary results showed that adding variable dosages of polyamine and 50% aluminium chlorohydrate combined coagulants dosages presented an improved particulate chemical oxygen demand, color, and turbidity removal efficiencies. The ascertained turbidity removal efficiency using the combined coagulation dosage of polyamine–aluminium chlorohydrate (PAC) treatment was 90.50% and 59.36% particulate chemcial oxygen demand removal, as comparable to polyamine alone with particulate chemical oxygen demand removal of 50% and turbidity of 75%. Likewise, an appreciable removal efficacy was observed as the aluminium chlorohydrate treatment alone was for particulate chemical oxygen demand and turbidity was 37% and 54%, respectively. In essence, this study emphasized the knowledge gap of the significant effect of the polymeric polyamine flocculant strength in adopting the combined coagulation dosage method to improve its coagulation efficiency and the high agglomeration on suspended solids, thereby, removing more of the unwanted inert contents from brewery wastewater. To determine zero liquid effluent discharge, this study clearly recommended an integrated treatment approach, microbial fuel cell integrated with a lab scale chemical coagulation technique for efficient non-biodegradable pollutant removal.

Microaerophilic treatment enhanced organic matter removal and methane production rates during swine wastewater treatment: A long-term engineering evaluation

Anaerobic biotechnology has been widely used for swine wastewater (SWW) treatment. However, its organic loading rate (OLR) is far lower than expected, mainly because of the low rate of hydrolysis. In this study, the comparative process performance and efficiency of an up-flow anaerobic sludge blanket (UASB) reactor (R1) and an up-flow microaerobic sludge blanket (UMSB) reactor (R2) were evaluated for SWW treatment, operating for 264 days under higher OLRs and lower hydraulic retention times than those found in the literature. The R2 was subjected to the three different air doses: 0.09 (stage I), 0.17 (stage II), and 0.25 (stage III) LO2 Lfeed−1 d−1 aiming at enhancing the hydrolysis step of the anaerobic digestion (AD). The overall results showed that 0.17 LO2 Lfeed−1 d−1 was the best experimental condition evaluated, which provided volatile suspended solids, total chemical oxygen demand, and particulate chemical oxygen demand removal efficiencies of 85.0 ± 1.9%, 83.8 ± 2.5%, and 82.1 ± 4.8%, respectively. This performance was due to the higher organic matter hydrolysis, resulting in higher methane production. Therefore, the UMSB reactor treatment was demonstrated to be a feasible alternative for SWW, although some strategies to control biomass washout must be investigated.

Performance of electrocoagulation and electro-Fenton processes for treatment of nanofiltration concentrate of biologically stabilized landfill leachate

In the present work, experimental study for leachate nanofiltration concentrate treatment by electrocoagulation and electro-Fenton processes using iron electrodes was carried out in a batch electrolytic reactor. Removal efficiencies of 60.2% for total organic carbon (TOC), 69.4% for chemical oxygen demand (COD), and 87.6% for color from the electro-Fenton process at the optimum operating conditions and 45% for TOC, 57.4% for COD, and 77.1% for color from the electrocoagulation process at the optimum operating conditions respectively, were obtained. Additionally the fraction of biodegradable COD increased from 6.37% to 17.04% and 30.08% after electrocoagulation and electro-Fenton processes respectively. About 39% soluble COD and 82% particulate COD removal efficiencies were obtained by electrocoagulation whereas 57% soluble COD and 81% particulate COD removal efficiencies were obtained by electro-Fenton process. Electro-Fenton process was found to be more effective than the electrocoagulation process with respect to the removal efficiencies of COD and TOC. However both processes could be efficient methods for converting nonsoluble COD to soluble COD and removal of nonbiodegradable COD. As a result both of the processes could be used as a post-treatment method for leachate and an effective method inert COD removal from leachate nanofiltration concentrate.

High-rate activated sludge processes for municipal wastewater treatment: the effect of food waste addition and hydraulic limits of the system.

Conventional activated sludge (CAS) process is one of the most commonly applied processes for municipal wastewater treatment. However, it requires a high energy input and does not promote energy recovery. Currently, high-rate activated sludge (HRAS) process is gaining importance as a good option to reduce the energy demand of wastewater treatment and to capture organic matter for valorizing through anaerobic digestion (AD). Besides, food waste addition to wastewater can help to increase the organic matter content of wastewater and thus, energy recovery in AD. The objective of this study is to evaluate the applicability of co-treatment of municipal wastewater and food waste in a pilot-scale HRAS system as well as to test the minimal hydraulic retention times (HRTs) such as 60 and 30min. Food waste addition to the wastewater resulted in a 10% increase in chemical oxygen demand (COD)concentration of influent. In the following stages of the study, the pilot-scale system was operated with wastewater solely under the HRTs of 60 and 30min. With the decrease of HRT, particulate COD removal increased; however, soluble COD removal decreased. The results demonstrated that if the settling process is optimized, more particulate matter can be diverted to sludge stream.

Development of a staged anaerobic pond for methane recovery from domestic wastewater

Since their inception in larger pond systems, the focus of anaerobic ponds has shifted from solids removal to optimising biogas production and reducing physical footprint to minimise land requirements. In this study, a horizontally baffled (HBAP) and vertically baffled (VBAP) anaerobic pond were compared. Distinct differences in the removal efficiency of COD fractions were observed, with particulate COD removal of 78% and 32%, and soluble COD removal of −26% and 19% in the HBAP and VBAP, respectively. A staged pond (SAP) was constructed through an HBAP placed upstream of a VBAP, with an additional HBAP used as a control (CAP). The SAP demonstrated superior biogas recovery potential over the control: methane production by the conclusion of the study was 6.09 and 9.04 LCH4 m−3 wastewater treated for the CAP and SAP, respectively. Methanogenic activity in the ponds was higher closer to the outlet, and hydrogenotrophic methanogenesis dominated over acetoclastic pathways.

High-rate activated sludge system for carbon management – Evaluation of crucial process mechanisms and design parameters

The high-rate activated sludge (HRAS) process is a technology suitable for the removal and redirection of organics from wastewater to energy generating processes in an efficient manner. A HRAS pilot plant was operated under controlled conditions resulting in concentrating the influent particulate, colloidal, and soluble COD to a waste solids stream with minimal energy input by maximizing sludge production, bacterial storage, and bioflocculation. The impact of important process parameters such as solids retention time (SRT), hydraulic residence time (HRT) and dissolved oxygen (DO) levels on the performance of a HRAS system was demonstrated in a pilot study. The results showed that maximum removal efficiencies of soluble COD were reached at a DO > 0.3 mg O2/L, SRT > 0.5 days and HRT > 15 min which indicates that minimizing the oxidation of the soluble COD in the high-rate activated sludge process is difficult. The study of DO, SRT and HRT exhibited high degree of impact on the colloidal and particulate COD removal. Thus, more attention should be focused on controlling the removal of these COD fractions. Colloidal COD removal plateaued at a DO > 0.7 mg O2/L, SRT > 1.5 days and HRT > 30 min, similar to particulate COD removal. Concurrent increase in extracellular polymers (EPS) production in the reactor and the association of particulate and colloidal material into sludge flocs (bioflocculation) indicated carbon capture by biomass. The SRT impacted the overall mass and energy balance of the high-rate process indicating that at low SRT conditions, lower COD mineralization or loss of COD content occurred. In addition, the lower SRT conditions resulted in higher sludge yields and higher COD content in the WAS.

Removal of residual dissolved methane gas in an upflow anaerobic sludge blanket reactor treating low-strength wastewater at low temperature with degassing membrane

In this study, we investigated the efficiency of dissolved methane (D-CH 4) collection by degasification from the effluent of a bench-scale upflow anaerobic sludge blanket (UASB) reactor treating synthetic wastewater. A hollow-fiber degassing membrane module was used for degasification. This module was connected to the liquid outlet of the UASB reactor. After chemical oxygen demand (COD) removal efficiency of the UASB reactor became stable, D-CH 4 discharged from the UASB reactor was collected. Under 35 °C and a hydraulic retention time (HRT) of 10 h, average D-CH 4 concentration could be reduced from 63 mg COD L −1 to 15 mg COD L −1; this, in turn, resulted in an increase in total methane (CH 4) recovery efficiency from 89% to 97%. Furthermore, we investigated the effects of temperature and HRT of the UASB reactor on degasification efficiency. Average D-CH 4 concentration was as high as 104 mg COD L −1 at 15 °C because of the higher solubility of CH 4 gas in liquid; the average D-CH 4 concentration was reduced to 14 mg COD L −1 by degasification. Accordingly, total CH 4 recovery efficiency increased from 71% to 97% at 15 °C as a result of degasification. Moreover, degasification tended to cause an increase in particulate COD removal efficiency. The UASB reactor was operated at the same COD loading rate, but different wastewater feed rates and HRTs. Although average D-CH 4 concentration in the UASB reactor was almost unchanged (ca. 70 mg COD L −1) regardless of the HRT value, the CH 4 discharge rate from the UASB reactor increased because of an increase in the wastewater feed rate. Because the D-CH 4 concentration could be reduced down to 12 ± 1 mg COD L −1 by degasification at an HRT of 6.7 h, the CH 4 recovery rate was 1.5 times higher under degasification than under normal operation.

Using the Kinetics of Biological Flocculation and the Limiting Flux Theory for the Preliminary Design of Activated Sludge Systems. I: Model Development

Current activated sludge models consider that the removal of biodegradable organics by suspended growth includes rapid enmeshment of the organic particles in the microbial floc, hydrolysis of the complex organic molecules into readily biodegradable organic substances, and oxidation of dissolved organic substances. All of the models assume hydrolysis is the rate-limiting step, but none consider the role that the kinetics of biological flocculation and the sludge settling characteristics may play in defining the activated sludge operating parameters. Several researchers have studied the kinetic of biological flocculation, and have analyzed its role on the removal of particulate COD in suspended growth reactors. It has been demonstrated that a large proportion of the organic matter present in sewage can be removed by biological flocculation using short hydraulic retention times and subsequent settling. This paper demonstrates that the one-dimensional limiting flux theory may be useful for coupling the sludge settling properties with the aeration tank behavior, and is a reasonable first approximation that can be used for activated sludge system design and operation.

The Role of Bioflocculation on Suspended Solids and Particulate COD Removal in the Trickling Filter Process

Understanding that there is a significant presence of extracellular polymeric substances at the biofilm/wastewater interface and that the primary constituent of chemical oxygen demand (COD) in domestic wastewaters is organic particulates, this research describes the kinetics of particulate removal in a pilot-scale trickling filter (TF) and the role of bioflocculation in the removal process. Recent research has described the role of bioflocculation on particulate COD (PCOD) removal in suspended growth biological wastewater treatment systems. However, no research pertaining to PCOD removal by bioflocculation in attached growth systems was identified prior to this study. For this study, experiments were conducted using both bench- and pilot-scale biofilm reactors and provided evidence that the removal of organic and inorganic particulate matter in a TF bioreactor follows a first-order bioflocculation rate equation. The statistical analysis of data obtained from the pilot TF fits the dispersion model to suspended solids and PCOD remaining in the pilot TF.

Decentralised treatment of concentrated sewage at low temperature in a two-step anaerobic system: two upflow-hybrid septic tanks

The decentralised treatment of concentrated sewage (about 3,600 mgCOD/l) at low temperature was investigated in a two-step anaerobic system: two-anaerobic hybrid (AH) septic tanks (each 0.575 m3). The two reactors were placed in a temperature controlled-room and the HRT was 2.5 days for each reactor. The system was fed with concentrated domestic sewage, mainly black water from about 40 toilets flushed with only 4 litre of water and a limited amount of grey water. The system showed high removal efficiency for the different COD fractions. Mean removal efficiencies in the two-step AH-septic tank at 5 days HRT and 13 degrees C were 94, 98, 74 and 78% for total COD, suspended COD, colloidal COD and dissolved COD respectively. The results of short run experiments indicated that the presence of reticulated polyurethane foam (RPF) media in the AH-septic tank improved the removal of suspended COD by 22%. The first AH-septic tank was full of sludge after 4 months of operation due to the high removal of particulate COD and the limited hydrolysis at low temperature conditions. Therefore, a simple mathematical model was developed based on ADM1 (the IWA model in 2002). Based on the experimental results and the mathematical model, only a one-step AH septic tank is required. An HRT of 5.5-7.5 days is needed for that one-step AH septic tank to treat concentrated sewage at a low temperature of 13 degrees C. Such a system can provide a total COD removal as high as 87% and will be full of sludge after a period of more than a year.

Nitrification in partially aerated flocculation filters - a full-scale approach

In a full-scale approach, we investigated whether nitrification can be carried out in partially aerated flocculation filters without compromising the removal of suspended solids. The objective is an aerated filter in addition to an advanced nitrification in the main biological treatment step to reduce low NH4-N concentrations in the effluent to very low concentrations. In two separate sets of experiments with an aerated filtering layer of 0.7 m and 1.4 m, nitrification rates up to 14 g N/(m3/h) were achieved. Compared to unaerated chambers, there was approximately the same removal of particulate COD and of precipitated phosphorus compounds. Due to the formation of anoxic zones, nonspecific denitrification occurred in the chambers under both conditions. Decay products are suspected to be the endogenous H-donors.

Nitrification in partially aerated flocculation filters — A full-scale approach

In a full-scale approach, we investigated whether nitrification can be carried out in partially aerated flocculation filters without compromising the removal of suspended solids. The objective is an aerated filter in addition to an advanced nitrification in the main biological treatment step to reduce low NH4-N concentrations in the effluent to very low concentrations. In two separate sets of experiments with an aerated filtering layer of 0.7 m and 1.4 m, nitrification rates up to 14 g N/(m3/h) were achieved. Compared to unaerated chambers, there was approximately the same removal of particulate COD and of precipitated phosphorus compounds. Due to the formation of anoxic zones, nonspecific denitrification occurred in the chambers under both conditions. Decay products are suspected to be the endogenous H-donors.

Organic carbon and nitrogen removal in moving-bed biofilm reactors

Pilot moving-bed biofilm reactors (MBBRs), fed on primary settled wastewater, were used in order to study organic carbon removal and nitrification. Nitrate uptake rate (NUR) tests were performed by feeding sodium acetate and potassium nitrate to a bench-scale moving-bed batch biofilm reactor. In both experiments the same polyethylene biofilm carriers were used. Both particulate and filtered COD removal rates appear to be proportional to the corresponding loading rates. Particulate COD removal is the net effect of adsorption onto and release from the biofilm surface. Filtered COD removal is the sum of the influent filtered COD removal and the removal of hydrolysed colloidal COD. Filtered COD removal rates could not be evaluated with a kinetic expression because back-diffusion from biofilm is not always negligible. Nitrification tests, performed at oxygen limiting conditions, show that the reaction rate was nearly first order with respect to dissolved oxygen due to liquid film diffusion. Denitrification batch tests showed denitrification rates very close to other reported data. Since the process proved reliable and easy-to-operate, it is suitable for application to small WWTPs, either in designing new plants or in upgrading existing overloaded activated sludge systems.

Organic carbon and nitrogen removal in moving-bed biofilm reactors

Pilot moving-bed biofilm reactors (MBBRs), fed on primary settled wastewater, were used in order to study organic carbon removal and nitrification. Nitrate uptake rate (NUR) tests were performed by feeding sodium acetate and potassium nitrate to a bench-scale moving-bed batch biofilm reactor. In both experiments the same polyethylene biofilm carriers were used. Both particulate and filtered COD removal rates appear to be proportional to the corresponding loading rates. Particulate COD removal is the net effect of adsorption onto and release from the biofilm surface. Filtered COD removal is the sum of the influent filtered COD removal and the removal of hydrolysed colloidal COD. Filtered COD removal rates could not be evaluated with a kinetic expression because back-diffusion from biofilm is not always negligible. Nitrification tests, performed at oxygen limiting conditions, show that the reaction rate was nearly first order with respect to dissolved oxygen due to liquid film diffusion. Denitriftcation batch tests showed denitrification rates very close to other reported data. Since the process proved reliable and easy-to-operate, it is suitable for application to small WWTPs, either in designing new plants or in upgrading existing overloaded activated sludge systems.

Comment on “degradation of non-diffusible organic matter in biofilm reactors” by Lars Rohold and Poul Harremoës, Wat. Res.27, 1689–1691 (1993)

Pilot moving-bed biofilm reactors (MBBRs), fed on primary settled wastewater, were used in order to study organic carbon removal and nitrification. Nitrate uptake rate (NUR) tests were performed by feeding sodium acetate and potassium nitrate to a bench-scale moving-bed batch biofilm reactor. In both experiments the same polyethylene biofilm carriers were used. Both particulate and filtered COD removal rates appear to be proportional to the corresponding loading rates. Particulate COD removal is the net effect of adsorption onto and release from the biofilm surface. Filtered COD removal is the sum of the influent filtered COD removal and the removal of hydrolysed colloidal COD. Filtered COD removal rates could not be evaluated with a kinetic expression because back-diffusion from biofilm is not always negligible. Nitrification tests, performed at oxygen limiting conditions, show that the reaction rate was nearly first order with respect to dissolved oxygen due to liquid film diffusion. Denitriftcation batch tests showed denitrification rates very close to other reported data. Since the process proved reliable and easy-to-operate, it is suitable for application to small WWTPs, either in designing new plants or in upgrading existing overloaded activated sludge systems.