Effect Of Hydraulic Loading Rate Research Articles

Removal of Per- and Polyfluoroalkyl substances by anion exchange resins: Scale-up of rapid small-scale column test data

Anion exchange (IX) is a readily implementable water treatment method that can effectively remove per- and polyfluoroalkyl substances (PFAS). The overarching objective of this research was to predict PFAS removal in full- or pilot-scale packed-bed IX resin contactors from rapid small-scale column test (RSSCT) data. Specific objectives were to (1) assess the effects of IX resin crushing on total anion exchange capacity and packed bed density, (2) determine the effects of initial PFAS concentration on PFAS uptake capacity, (3) determine the rate-limiting step controlling PFAS uptake kinetics, (4) determine the effects of hydraulic loading rate on PFAS uptake capacity, and (5) link constant diffusivity RSSCT data to pilot test data to develop a scale-up protocol. Experiments were conducted with two single-use IX resins and three water matrices, including coagulated surface water and groundwater.Crushing IX resin did not substantially change the bed density and total anion exchange capacity, but the morphology of particles changed from almost perfectly spherical to irregularly shaped. PFAS uptake capacity was independent of influent PFAS concentrations in the 30–300 ng/L range. This finding facilitated the development of an RSSCT scale-up approach because influent PFAS concentrations in RSSCTs and corresponding pilot tests often differ. Biot number values and data from interrupted RSSCTs demonstrated that film diffusion or a combination of film diffusion and intraparticle diffusion controls the rate of PFAS uptake by IX resins. From RSSCTs with identical empty bed contact times but different hydraulic loading rates (vf), PFAS uptake capacity was found to be a function of the square root of the product of Sherwood number and particle shape factor (Sh×ϕ). Using a constant diffusivity RSSCT design with a reduced vf, full- or pilot-scale PFAS breakthrough data can therefore be predicted by multiplying the bed volumes of water treated in the RSSCT by a factor of (Shpilot×ϕpilot)/(ShRSSCT×ϕRSSCT) . This research will support the design of future IX treatment processes in the context of PFAS remediation and drinking water treatment.

Effect of Hydraulic Loading Rate on Treatment Performance of a Pilot Wetland Roof Treating Greywater from a Household

To solve the upcoming environmental problems, sponge city concepts as well as new technologies are being developed these days. One of the future challenges is to reduce drinking water demand by using decentralized water recycling systems. This study aimed to investigate the performance of a specially designed pilot wetland roof (PWR) treating domestic greywater (GW) at ground level under outdoor conditions and to evaluate the effects of different hydraulic loading rates (HLRs) for a period of two years. The results showed highly efficient removal of typical greywater pollutants from the system, e.g., five-day biochemical oxygen demand (BOD5) > 96%, chemical oxygen demand (COD) > 93%, total suspended solids (TSS) >94%, anionic surfactants (AS) > 94%, ammonium-nitrogen (NH4-N) > 84%, total nitrogen (TN) > 71%, total phosphorous (TP) > 87%, and E. coli (1.86 ± 1.54 log-removal). The mean concentrations of the targeted parameters at the outflow were in compliance with the requirements for discharge to the environment and met reclaimed water quality standards for agricultural irrigation, except for E. coli. Statistically significant (p < 0.05) results of pollutant mass removal rate across different HLRs indicated the potential effect of HLR on treatment performance, and HLR in a range of 67–80 L m–2 d–1 contributed to a higher removal efficiency without compromising the limit values. A comparatively low HLR of 45 L m–2 d–1 should be applicable if pathogen removal is the most important requirement. Plant species showed good plant vitality and adapted well to the water storage mat. The higher the mean ambient air temperature, the greater runoff reduction (>50%) was observed due to high evapotranspiration. The results showed the system is a promising green technology for GW recycling and can be scaled up for application to urban buildings.

Effect of Hydraulic Loading Rate on Production of Tomato (Solanum Lycopersicum) with Pearlspot (Etroplus Suratensis) in Recirculating Aquaponic System

An experiment was conducted to evaluate the effect of hydraulic loading rate (HLR) on tomato (Solanum Lycopersicum) with pearlspot (Etroplus suratensis) in a recirculating aquaponic system. The experiment consisted of three treatment groups with different HLR of 3 m.day-1 (T1), 6 m.day-1 (T2), and 12 m.day-1 (T3); while the control (C) group had HLR of 3 m.day-1 without plants. Tomato and pearlspot were stocked at 4 plants.m-2 and 0.86 kg.m-3 (142 no.m-3 with an average initial weight of 6.06±0.09 g), respectively. The results indicated that the HLR had profound influence on the growth of both plant and fish. Tomato growth was highest in T1 (1.60±0.04 kg.m-2), followed by T2 (1.35±0.05 kg.m-2) and T3 (1.09±0.069 kg.m-2). Pearlspot growth was highest in T2 (13.57±0.04 g), followed by T1 (13.48±0.04 g), T3 (13.17±0.01 g), and C (13.00±0.28 g). The removal of nitrate (65.71%), phosphate (46.43%), and potassium (62.74%) was highest in T1, followed by T2, T3, and C. Based on the tomato and pearlspot growth as well as the maximum nutrient removal, a HLR of 3.0 m.day-1 can be recommended for tomato and pearlspot production in an aquaponic system.

Effects of hydraulic loading rate and substrate on ammonium removal in tidal flow constructed wetlands treating black and odorous water bodies

The efficient removal of ammonium nitrogen (NH4+-N) is vital to eliminating black and odorous water bodies. In this work, tidal flow constructed wetlands with gravel (TFCW-G) and with a mixture of zeolite and gravel (TFCW-Z) were set up to treat black and odorous water bodies at different hydraulic loading rates (HLRs). Results showed that zeolite significantly enhanced nitrogen removal, and the maximum NH4+-N removal efficiency of 96.69% was achieved in TFCW-Z at HLR of 3 m·d−1 with a flooding and drying cycle of 2 h. Zeolite addition changed the microbial community structure and the abundance of nitrification genes. Comammox Nitrospira was the only enriched strain accounting for NH4+-N removal in TFCW-G, while the co-occurrence of comammox Nitrospira and the canonical and potential ammonia-oxidizing bacteria were identified in TFCW-Z. Summarily, high performance, together with low footprint and low maintenance cost, are characteristics that make the TFCW-Z a promising and competitive alternative.

Effects of Hydraulic Loading Rate on Spatial and Temporal Water Quality Characteristics and Crop Growth and Yield in Aquaponic Systems

Aquaponics is a rapidly growing food-production system integrating aquaculture and hydroponic crop production through an energy-intensive water recirculation process. Crop performance and yield in aquaponics are affected by essential and toxic nutrient levels in the root zone, which can be regulated by water flow rate. This study was conducted to examine the effects of hydraulic loading rate (HLR) on water quality and crop growth and yield in recirculating aquaponic systems set at three different loading rates: high (3.3 m3/m2/day; HFR, which is 12 times lower than recommended loading rate), medium (2.2 m3/m2/day; MFR), and low (1.1 m3/m2/day; LFR). Crop species varying in growth rate were examined for their optimal HLR: fast-growing Chinese cabbage (Brassica rapa) and lettuce (Lactuca sativa); medium-growing mustard (Brassica juncea) and chia (Salvia hispanica); and slow-growing basil (Ocimum basilicum) and Swiss chard (Beta vulgaris). Compared to LFR, HFR decreased water and leaf temperatures and total ammonium nitrogen (TAN) but increased dissolved oxygen and pH in aquaponic solution up to one and two weeks after transplant, respectively. HFR increased NO3–N concentration by 50 and 80%, respectively, compared to MFR and LFR, while reducing the exposure duration of roots to ammonia (NH3–N) and its peak concentration through rapid dissipation of the toxic compound. Lower electrical conductivity (EC) in HFR during the last two weeks of production was associated with higher plant nutrient uptake and greater biomass production. The leaf greenness, photosynthetic rate (Pn), and total plant N were significantly higher at HFR than LFR. Fish growth rate, fresh weight, and feed-conversion efficiency were also increased by HFR. The growth of fast-growing crops including total fresh weight, shoot fresh weight, leaf area, and Pn was not different between HFR and MFR, while HLR had less significant effects on the growth and performance (i.e., shoot fresh weight and whole plant photosynthesis) of slow-growing crops. In conclusion, the flow rate is an important component in aquaponic crop production as it affects spatial and temporal water characteristics and subsequently determines the growth and yield of the crops. HLR at 3.3 m3/m2/day was sufficient across the crops allowing better chemical and physical properties of the aquaponic solution for maximum yield and quality. HLR should be maintained at least at 2.2 m3/m2/day for the production of fast-growing crops but can be lowered for slow-growing crops.

Combined Vertical-Horizontal Flow Biochar Filter for Onsite Wastewater Treatment—Removal of Organic Matter, Nitrogen and Pathogens

This study investigated the performance of a combined vertical-horizontal flow biochar filter (VFF-HFF) system in terms of organic matter, total nitrogen (Tot-N), Escherichia coli and Salmonella removal and explored the effects of hydraulic loading rate (HLR) on pollutant removal. The combined VFF-HFF system used biochar as the filter medium and comprised two stacked sections: (i) an aerobic vertical flow filter (VFF) in which the wastewater percolated through the biochar medium in unsaturated mode and (ii) a horizontal flow filter (HFF), in which the biochar was saturated with water and had limited access to air, to enable anaerobic conditions and enhance the denitrification process. The system was tested over 126 weeks using real wastewater applied at different HLR (23, 31, 39 L m−2 day−1). The results showed that long-term removal of organic matter in the entire system was 93 ± 3%, with most (87 ± 5%) occurring in the VFF. For Tot-N, the long-term removal was 71 ± 12%, with increasing trends for nitrification in the VFF and denitrification in the HFF. Mean long-term nitrification efficiency in the VFF was 65 ± 15% and mean long-term denitrification efficiency in the HFF 49 ± 14%. Increasing HLR from 23 to 31 L m−2 day−1 increased the nitrification efficiency from 42 to 61%. Increasing the HLR further to 39 L m−2 day−1 decreased the denitrification efficiency from 45 to 25%. HLR had no significant effects on VFF and HFF performance in terms of E. coli and Salmonella removal, although the VFF achieved a 1.09–2.1 log10 unit reduction and the HFF achieved a 2.48–3.39 log10 unit reduction. Thus, long-term performance, i.e., removal of pollutants measured during the last 52 weeks of the experiment, was satisfactory in terms of organic matter and nitrogen removal, with no signs of clogging, indicating good robustness of the combined VFF-HFF biochar filter system.

Effect of hydraulic loading rate on the growth of koi carp (Cyprinus carpio var. koi.) and Gotukola (Centella asiatica (L.)) using phytoremediated aquaculture wastewater in aquaponics

The study evaluates optimum hydraulic loading rate (HLR) based on the fish and plant production performance and nutrient removal percentage in aquaponics. The growth of Gotukola (Centella asiatica (L.))—a leafy vegetable as well as traditional medicinal plant—and koi carp (Cyprinus carpio var. koi.)—a high demand ornamental fish—were evaluated at three different HLRs, viz. 2.6 m day−1 (T1), 7.8 m day−1 (T2), and 13.0 m day−1 (T3). Treated aquaculture wastewater was utilized in a combination of the freshwater in 1:1 ratio with 2.1 kg m−3 fish stocking density. The highest fish mean length; weight; feed conversion ratio; specific growth rate; NH3, NO2−, and NO3− removal percentage; and plant growth parameters were observed. Considering fish (koi carp) and plants (Gotukola) growth parameters as well as nutrient removal percentages, a HLR of 7.8 m day−1 was found to be the optimum in aquaponics.

Effect of hydraulic loading rate and vegetation on phytoremediation with artificial wetlands associated to natural swimming pools

Abstract The treatment of pool water, whether for recreational or sporting purposes, by phytoremediation is widely applied. This work evaluates two artificial vertical flow wetlands, one on a real scale and the other on a laboratory scale, which have been planted with Typha domingensis, for the treatment of pool water in the climatic conditions of the city of Santiago de Cuba. When the hydraulic load applied to the real scale wetland was less than 0.25 m3∙m–2∙d–1, the levels of organic and microbiological contamination in the pool were below the maximum limits allowed by Cuban standards. At a laboratory scale, the presence of vegetation favoured the elimination of nitrogen compounds (nitrates and ammonium) and organic materials (BOD and COD). This behaviour is explained by the presence of processes of assimilation of organic compounds, or by the action of microorganisms associated with the rhizome of plants, which establish a symbiotic mechanism favourable to phytodepuration. The minimum concentration of ammonium obtained in outflow from the laboratory-scale reactor without vegetation reached a value of 2.15 mg∙m–3, which is within the limits allowed by the sanitary regulations.

Effect of aeration and hydraulic loading rate on nitrogen removal by subsurface infiltration systems.

This study investigated the effect of hydraulic loading rate (HLR) on matrix dissolved oxygen (DO), organic matter removal, nitrogen removal, N2 O emissions, and the abundances of functional genes participating in nitrogen removal in intermittent aerated mode (IAM) and nonaerated mode (NAM) subsurface infiltration systems (SISs). In contrast to NAM SISs, IAM SISs were able to create aerobic conditions in the upper matrix (above 50cm depth) and anoxic or anaerobic conditions in the lower matrix (below 80cm depth). Subsequently, this enhanced the abundance of functional genes related to nitrogen removal. Chemical oxygen demand (COD) and nitrogen removal performance were significantly higher under IAM SISs than with NAM SISs. Under a HLR of 0.3m3 /(m2 d), the IAM SIS was able to achieve low N2 O emissions (12.6mg/[m2 d]) along with removal efficiencies of 90.5%, 91.4%, and 85.7% for COD, ammonia nitrogen ( -N), and total nitrogen (TN), respectively. PRACTITIONER POINTS: Intermittent aeration successfully realized sequential aerobic and anaerobic conditions at 50 cm depth and at 80 and 110 cm depths of a subsurface infiltration system. Intermittent aeration reduced N2 O emissions and improved hydraulic loading rate and organic matter, nitrogen removal efficiencies. Intermittent aeration enhanced the abundances of amoA, nxrA, napA, narG, nirS, nirK, qnorB, and nosZ.

Nutrient removal from high ammonium swine wastewater in upflow microaerobic biofilm reactor suffered high hydraulic load

To understand the ability of an upflow microaerobic biofilm reactor (UMBR) to remove nutrient from manure-free swine wastewater rich in NH4+ with a COD/TN ratio less than 1.00, effect of hydraulic loading rate (HLR) on the microaerobic process was evaluated with a constant reflux ratio of 25 at 25 °C. The results showed that changes in HLR had a remarkable effect on the performance of the UMBR in nutrient removal from the wastewater. With the favorable HLR 3.0 m3/(m3·d) (Hydraulic Retention Time (HRT) 8 h), average removal of COD, NH4+ and TN in the microaerobic process reached 59.3%, 87.7% and 84.7%, respectively, though the COD/TN ratio was as low as 0.84. With an over HLR of 4.0 m3/(m3·d) (HRT decreased to 6 h), bad performance of the UMBR was observed with an average removal of COD, NH4+ and TN as low as 45.0%, 59.0% and 57.5%, respectively. Since the HLR was decreased to 2.4 m3/(m3·d) (HRT 10 h), the microaerobic process regained the efficiency in nutrient removal with a removal of COD, NH4+ and TN averaged 59.0%, 95.3% and 87.8%, respectively. The microaerobic condition allowed anammox bacteria, ammonia-oxidizing bacteria and archaea, nitrite-oxidizing bacteria and denitrifiers to all thrive in the UMBR, resulting in the efficient synchronous removal of organic carbon and nitrogen. As the dominant approach to nitrogen removal, anaerobic ammonium oxidation (anammox) pathway contributing to the TN removal in the microaerobic process exceeded 59.5% at HLR 3.0 m3/(m3·d). The results demonstrated that the UMBR can remove nitrogen and carbon from swine wastewater, with a suitable HLR.

Effects of Hydraulic Loading Rate on Nutrients Removal from Anaerobically Digested Swine Wastewater by Multi Soil Layering Treatment Bioreactor.

A multi soil layering (MSL) treatment bioreactor was developed aiming at nutrients removal from anaerobically digested swine wastewater (ADSW). The start-up of the MSL bioreactor and its performance in nutrients removal at different hydraulic loading rate (HLR) were investigated. Results showed that the MSL bioreactor was successfully started up after operation for 28 days, and at this time, the removal efficiencies of ammonia-N, total nitrogen (TN) and total phosphorus (TP) in the ADSW reached 63.6%, 58.5%, and 46.5%, respectively. The MSL bioreactor showed a stable performance during the whole working process with varying HLR from 80 to 200 L/(m2·day). Maximum removal efficiencies of ammonia-N, TN and TP were obtained at 160 L/(m2·day), and was appeared as 94.2%, 94.4%, and 92.5%, respectively. It was worth noting that iron scraps were the key factor that enhanced the independent capability of the MSL bioreactor in TP removal, because there was only 21.4–25.8% of the TP was removed when the MSL bioreactor run with no iron addition.

Effects of hydraulic loading rate and organic load on the performance of a pilot-scale hybrid VF-HF constructed wetland in treating secondary effluent

This study evaluated the performance of a pilot-scale hybrid constructed wetland system for secondary effluent and investigated bulk organic matter characteristics. The hybrid constructed wetland consisted of a vertical-flow (VF) bed followed by a horizontal-flow (HF) bed. We also investigated the effects of hydraulic loading rates and influent organic load on the performance of the pilot-scale VF-HF hybrid constructed wetland. The results showed a high removal efficiency for suspended solids (>95%) and organic matter as determined by total organic carbon (>98.5%) and dissolved organic carbon (>70%), but no significant change in nitrogen removal was observed. The wetland treatment efficiency for suspended solids and organic matter showed a good buffer capacity even when hydraulic loading rates increased from 750 to 1500 L m−2 d−1 and 500–1000 L m−2 d−1 during the VF and HF stages, respectively. Moreover, there was no significant change in the performance when influent organic load increased eight-fold. Fluorescence excitation-emission matrix and liquid chromatography-organic carbon detection (LC-OCD) were used to investigate the dissolved organic matter characteristics in the hybrid VF-HF constructed wetland. Fluorescence excitation-emission matrix spectroscopy showed that both protein- and humic-like substances did not significantly change in the effluent when hydraulic loading rates and organic load increased by two- and eight-fold, respectively. Biopolymers determined using LC-OCD were effectively removed via the VF and HF stage wetlands, indicating the occurrence of biodegradation. Fluorescence excitation-emission matrix spectroscopy and LC-OCD provided the fate of dissolved organic matter characteristics in the hybrid VF-HF constructed wetland.

Feasibility investigation of a multi soil layering bioreactor for domestic wastewater treatment

ABSTRACTIn this study, a multi soil layering (MSL) bioreactor was constructed to treat synthetic domestic wastewater. Effects of hydraulic loading rate (HLR) on the performance of the MSL bioreactor for synthetic domestic wastewater treatment were investigated. Results showed that the MSL bioreactor exhibited a strong adaptability on the variation of HLR, when the HLR was adjusted to 400 L·m−2·d−1, average removal efficiencies of chemical oxygen demand (COD), ammonia, total nitrogen (TN), and total phosphorus (TP) reached 93.4%, 94.9%, 80.4%, and 94.7%, respectively, which meet to the 1A discharge standard of the Discharge standard of pollutants for municipal wastewater treatment plant (GB 18918-2002). In the treatment process by the MSL bioreactor, biological decomposition and biotransformation processes of microorganisms was the most important pathway for COD, ammonia, and TN removal, while TP was removed by the chemical reaction with ferric ion. Nitrobacteria, ciliate, rotifer and epistylis were in large numbers in the operating phase, indicated that the biofilm was matured with a high quality and the MSL bioreactor was effective for domestic wastewater treatment.

Effect of hydraulic loading rate and pollutants degradation kinetics in two stage hybrid macrophyte assisted vermifiltration system

Three cylindrical vertical flow (VF) (1st stage) and three horizontal flow (HF) vermifilters (2nd stage) were designed and planted with Canna indica to study the effect of HLR. The vermifilters were loaded (to VF) with synthetic dairy wastewater at three HLRs of 0.3, 0.6 and 0.9 m d−1 and operated for 100 days. Removal rate constants were higher at HLR 0.6 m d−1 and the value of KBOD5, KCOD, KNH4+-N, KTN, KTP (for VF + HF unit) were 0.51, 0.41, 0.32, 0.23, 0.26, respectively. Efficiency of VF reactor were higher than HF reactor in case of all types of pollutants. The average removal of BOD5 was found to be 90.43% at HLR 0.3 m d−1 and 85.75% at HLR 0.6 m d−1, while for COD it was found to be 85.59% and 79.64%, respectively. In the present study, the overall theoretical oxygen transfer rate (OTR) for HLR 0.3, 0.6 and 0.9 m d−1 (VF + HF unit) were 36, 92 and 195.6 g m−2 d−1, respectively. The OTR value for HF reactor was very less. The present value is much higher than other studies and it may be due to earthworm respiration and their burrowing and tunnelling activities. The percentage increase of earthworm number in all VF reactors were in the range of 28.3–31.5 and in HF reactor in the range of 19.1–26.2.

Factors affecting the performance of horizontal flow constructed treatment wetland vegetated with Cyperus papyrus for municipal wastewater treatment

ABSTRACTThe effect of hydraulic loading rate (HLR) and hydraulic retention time (HRT) on the bioremediation of municipal wastewater using a pilot scale subsurface horizontal flow constructed treatment wetland (HFCTW) vegetated with Cyprus papyrus was investigated. Different HLRs were applied to the treatment system namely 0.18, 0.10, and 0.07 m3/m2. d with corresponding HRTs of 1.8, 3.2, and 4.7 days, respectively. The flow rate was 8 m3/d, and the average organic loading rate (OLR) was 0.037 kg BOD/m3/d. Results showed that the performance of the HFCTW was linearly affected by decreasing the HLR and increasing the HRT. The highest treatment efficiency was achieved at HRT (4.7 days) and HLR (0.07 m3/m2. d). The percentage reductions of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) were 86%, 87%, and 80%, respectively. Satisfactory nutrient removal was obtained. Also, removal of 2–3 logs of bacterial indicators of pollution was achieved. The dry biomass of Cyperus was 7.7 kg/m2 and proved to be very efficient in nitrification processes due to high diversity of the roots that increase the treatment surface area.

The Effect of HLRs on Nitrogen Removal by Using a Pilot-scale Aerated Steel Slag System

Discharge from domestic wastewater treatment plant amongst the main sources of nitrogen pollution in the environment. However, to remove nitrogen conventionally in domestic wastewater require high cost and complex chemical treatment method. Vertical flow aerated rock filter emerged as one of attractive alternative wastewater treatment method due to simplicity and compactness of the system. However, the application is yet to be developed in warm climate countries in particular Malaysia. Therefore, this study was conducted to investigate the effect of hydraulic loading rate (HLR) to the performance of a pilot-scale Vertical Flow Aerated Rock Filter (VFARF) in removing nitrogen from domestic wastewater using pilot-scale VFARF systems with steel slag as the filter media. Furthermore, this study has been designed to focus on the effects of two HLRs; 2.72 and 1.04 m 3 /m 3 .day. Influent and effluent of the filter systems were monitored biweekly basis for 11 weeks and analyzed for selected parameters. Results from this study shows that the VFARF with HLR 1.04 m 3 /m 3 .day has performed better in terms of removal ammonium-nitrogen and TKN as the system able to remove 90.4 ± 6.9%, 86.2 ± 10.7%, whilst the VFARF with 2.72 m 3 /m 3 .day remove 87.4 ± 9.9%, 80 ± 11.7%, respectively. From the observation, it can be concluded that nitrogen removal does affect by HLR as the removal in lower HLR system was higher due to high DO level in the VFARF system with 1.04 m 3 /m 3 .day which range from 4.5 to 5.1 mg/L whilst the DO level was slightly lower in the VFARF system with 2.72 m 3 /m 3 .day in the range of 3.7 to 4.5 mg/L.

Effects of Hydraulic Loading Rate on the Removal of Pollutants from an Integrated Biological Settling Tank

Based on the designing concepts of rotating biological disk and settling tank, a hybrid biological purification and settling tank was developed to achieve simultaneous removal of turbidity causing materials, organic matters, NH4+-N, and TP. Experimental results showed that under certain rotary speed and water quality conditions, the removal rates of both turbidity and organic matters and NH4+-N were relatively stable first and then started to decrease with the increase of hydraulic loading rate. The highest value was achieved at 0.036 g·(m2·d)-1 and 0.064 g·(m2·d)-1 respectively. Compared with turbidity and TOC and NH4+-N, the removal rate of TP was greatly influenced by hydraulic loading rate. The average TP removal was the worst at 0.064 g·(m2·d)-1. Appropriately decreasing or increasing the hydraulic load was helpful to the phosphorus removal process. Further study showed that nitrification and dephosphorization processes competed for the limited carbon source and DO in the water phase. Along the flow direction, the surface of the disc populations of microorganisms with good coordination and distribution along the characteristics ensured that the process still had certain decontamination effect under the condition of unfavorable hydraulic load, which indicated that the biological settling tank had a capacity in resisting organic loading rate shock and could be used in enhancing pollutant removal in treating micro-polluted water.

Performance evaluation of an Integrated On-site Greywater Treatment System in a tropical region

Integrated On-site Greywater Treatment System (IOGTS) with primary (settling/filtration), secondary (constructed wetland) and tertiary (adsorption) treatment was used to treat greywater from hostel. A field scale IOGTS was constructed for hostel located in Sakharale, District Sangli (M.S.) India. The performance evaluation of IOGTS was carried out for a study period of one year. The quality parameters used to assess feasibility of disposal for land application were COD, TKN, suspended solids, and pathogens. The effect of hydraulic loading rate (HLR), Hydraulic Retention Time (HRT) and Organic Loading Rate (OLR) on performance of the system was also studied. A consistent performance (30% COD removal and 70% turbidity removal) was observed in upflow-downflow filter throughout the study. Secondary treatment in IOGTS was evaluated for HLR (10–100mm/d) and OLR (10–350kg COD/ha.d). HLR (40mm/d) and OLR (170kg COD/ha.d) showed a better removal efficiency of COD. Overall performance of IOGTS for COD, TKN and pathogen removal was observed to be 70%, 70% and 85% respectively. Therefore, IOGTS can be considered to be an appropriate treatment option to treat greywater to satisfy effluent standards for its reuse in land application.

Effect of hydraulic loading rate on pollutant removal efficiency in subsurface infiltration system under intermittent operation and micro-power aeration

The low hydraulic loading rate (HLR) greatly restricts the wide application of subsurface wastewater infiltration system (SWIS) in densely populated areas. To increase the HLR, an innovative SWIS was developed using cyclic operation mode. In each cycle, a wastewater feeding period is followed by a drying period, in which the aeration is conducted by a medium-pressure fan. Results indicated that the removal rate of TOC and NH4+-N were more than 85% at HLR of 0.5m3/m2d, whereas the TN removal rate was lower than 20%, indicating that the aeration was efficient and denitrification process was largely limited in the SWIS. When HLR decreased from 0.5 to 0.2m3/m2d, the pollutant removal efficiency enhanced slightly except for TN. Overall, the intermittent operation and micro-power aeration, combined with shunting the pollutant loading were really helpful for SWIS to achieve higher HLR, which offers a reference for the design of innovative SWIS.

Study of nitrogen removal performance in pilot-scale multi-stage vermi-biofilter: operating conditions impacts and nitrogen speciation transformation

The present work investigates pollutant removal and the transformation of nitrogen from sewage wastewater using a pilot-scale multi-stage bio-vermifilter system. Over a study period of 48 weeks, the pollutant removal performance of the system was measured and the effects of hydraulic loading rate (HLR) and dry–wet ratio (D/W) were estimated. The relationship between oxygen transfer rate and load of oxygen necessity was calculated and analysed for system optimisation. The method for diluting the isotope δ15N-NO3 − was applied to study nitrogen transfer. Moreover, statistical correlations were analysed to determine the crucial factors which influence nitrogen transfer efficiency. The system removes pollutants efficiently; specifically, the average removal efficiencies are 94.2 % for chemical oxygen demand (COD), 93.3 % for NH4 +-N, and 58.2 % for total nitrogen (T-N). Lowering HLR and D/W can enhance nitrogen removal. Nitrogen speciation and transformation were examined under an optimised condition with an HLR of 0.36 m day−1 and a D/W of 3. The results of isotope δ15N-NO3 − dilution showed that NO3 −-N was mainly produced in trickling bio-filter and vermibio-filter (VBF) I. By contrast, NO3 −-N was mainly reduced in VBF II. Under stable operating conditions and environmental factors, COD/T-N was verified as the crucial factor in nitrogen removal.